The Stovebolt Site Forums The Shop Area The Electrical Bay Reducing voltage at heater blower -- something different?

I've finished converting our '55 to 12vdc. Now I would like to run the 6vdc heater motor without burning out. Sourcing a comparable 12vdc motor isn't an option as it is too pricey here in Canuckland.

I tried using a 1 ohm, 50 watt wire wound resistor in series with the OEM rheostat switch. It kinda works but the fan runs quite a bit slower than it did with its native 6 volts applied. And that annoyance is compounded as the rheostat switch is turned for speed control (fan stops on LOW (input becomes more restricted at 2.2vdc)). Paralleling two 1 ohm resistors (equals .5 ohm) makes the fan run much faster across its speed spectrum but the controlling rheostat switch now heats up to the point of almost burning up!

Now it's time to try something different: using a 12v>6v step-down reducer (Buck converter). I see one on eBay that is fully adjustable input and output. Max current output is 12 amps -- plenty for this heater motor (it draws 5.75 amps @ 6.8 volts)

I would like your expert take on this device -- will it do the job? -- thanks.

http://www.ebay.com/itm/DC-DC-CC-CV...12A-EC-/221670461819?hash=item339c96d17b

For less than five bucks, give it a shot and report back
to us on the results.
It's probably using something like a pair of the LM2596
voltage regulators to get the higher current capacity.
These are switching power supplies and convert DC to AC
at a high frequency which allows them to step it down (buck)
or step it up (boost) it to the lower or higher voltage thru
an inductor.
Then it's rectified and filtered converting it back to a DC
output. These typically have an efficiency over 90%.
I may be wrong but I think these can generate some RF electrical
noise and may interfere with receiving devices.
The voltage booster cubes are similar circuits and I use a 5A
one to power my 12v tach and Sony AM/FM/CD player on my stock
6v system.

DG

There is a simple way to address the problem- - - -use a speed control resistor designed for multi-speed fans on 12V systems that mount inside the air box with air flowing over it to control the heat generated. By connecting the various speed control windings in parallel, you can get the speed you're looking for. Virtually all 12V climate control systems have those reisitors- - - -go junkyard scavenging and find one you can adapt to your application.
Jerry

I use a BWD VR1 resistor in line with mine. So far no problems, but I don't use the heater motor often.

Bill

Yeah, I wonder how it would work with a non-static motor load?

So, if the output voltage can be set to say, 6.5vdc, then the heater & switch will draw whatever amperage is needed -- is that how it works?
Or would the amperage have to be preset somehow, and if that's the case, it may again overheat the switch ..hmm.

Another one I found is here: http://www.prodctodc.com/dc-1035v-t...24v-to-6v-7a-42w-p-190.html#.VeiPUM-FOPx
But it's fixed at 6 volts, 7 amps.

Interesting idea.

A while back a friend did let me scavenge from his old derelict '79 Bronco.

Thinking it might work out, I scooped the 12 volt heater blower motor and resistor array from the heater box.
The (vented) blower motor was rusty inside (hood was left open) and had a big shroud mounted to it as part of the casing (still spins though).

The resistor array is still in one piece albeit also rusty -- but useable. My concerns are a)having to cut into the vintage heater box to properly mount it b)having enough cooling airflow over it from the puny 6 volt motor and 4-blade fan c)mounting an ugly non-OEM 3-speed non-rheostat switch in/under the dash.

Similar device as I reported in the original post ..with the resulting problem: much slower speeds especially past the HI position.
Yes, in this PNW climate, the heater can be used a lot in Winter.

As Bill suggests. This is an Echlin part, Chart says one of these is good for 4 amps, put two in parallel for up to 8A. Cheap, easy. The reason it won't perform in Hi: You need two of these in parallel!!!! If your draw is 6A.
Buy here or Napa VT6187
You don't want a live PC board under dash, full of soldered components, mounted to what? How do you wire to it? Forget that thing. This part Bill mentioned is for trucks baby, stud mounted and tough screw terminals. Yeah!
FYI: Those switches are always Hot. That's why they have ceramic bodies and are mounted away from other components. As you can see, the reducer is also ceramic. When you see ceramic, think it's going to get hot. Other switches are not insulated that way. Don't fret over it.

So it's an Echlin part.. still just a big resistor though, which I've already explained will not work satisfactorily. Yes, when 2 high-watt resistors are in parallel it does spin well on HI, but then the OEM rheostat switch (connected in series) starts to smoke in MED position.
Aside from replacing the 6 volt motor with a 12 volt edition, I'm thinking that using a dropping resistor is kind of a crappy inefficient way of trying to address the problem.

So I've kinda exhausted that round of tests.

Methinks, I can figure a way to properly mount a Buck converter into the airstream -- perhaps others here have some suggestions as to how??
Of course an appropriate fuse will be ahead of it.
As referred to above, this alternative device has no exposed components. http://www.prodctodc.com/dc-1035v-t...24v-to-6v-7a-42w-p-190.html#.VeiinM-FOPy
But it has limited output and not adjustable, contrary to the one on eBay.

If you use a component that is made to reduce 12V to 6V and it will handle your amp draw and it smokes a simple speed switch, you are missing something, it defies logic or have a bad motor or switch or wiring. You can go off into electronics land if you want to but this is pretty simple. Did you measure to see you were getting 6V and any amp draw changes at speed levels in your "experimental" efforts? The tech tip section here says use a voltage reducer. This is common practice and the ones linked are designed for automotive use and exactly what you are doing. They will reduce the voltage from 12 to 6, two in parallel will handle up to 8A.(assume your mention of 5.75A is max draw). So that set up will work if other components are working properly. The switches will be hot at mid range, Very hot. Normal. (Not smoking hot.) The resistor is dissipating the energy that would go to motor because it is causing motor to operate slower. If it smokes, again, bad switch, motor, wiring or all three. Are you using the word smoke as just an expression? Do you have the heater blower motor/switch fused? If fused, it will blow before smoke. Fuses are for protecting switches and fan motors, etc. Make sure fuse is not too big. I see you took out motor, did you check fins, rotation, clogging, rubbing, wiring, worn brushes, dry on oil?????? I see you got it running backwards, then "fixed it", I see it's a GMC heater someone put in. Is this a Chevy or GMC "first series"? Methinks you better redo this heater motor and bench test before installing.

When you reduce down to 6 volts, reduce the entire heater circuit including the original switch and the tri-lead resistor on the back. Thats all there is to it. Now everything works as it did in 6 volts and the only thing that gets crazy hot is that 12-6v reducer.

Or do this: http://devestechnet.com/Home/HeaterRestore

12v motor will run you about $50 and then for your original switch, get 2 one ohm 10 watt resistors and replace the one on the back of the switch. Might run about $55 total plus shipping. I have the two resistors but havent gotten around to updating the page yet. There are a few things I want to test before putting it out there as far as placement, wiring, etc.

Some great suggestions here -- thanks.

The switch did 'smoke' but it was probably due to some contaminant in it. Otherwise, it was just really hot with one of the exposed internal coil glowing.
I didn't like that observation especially as it would normally be mounted behind and through the dash.

The motor seems to spin ok once I put it back together. The bearings were reoiled, the brushes looked fine.
Thing is the motor does draw more amps if not spinning in its normal position: horizontal -- which it wasn't when on my bench --I had it propped up with it's hot water pipes holding it up, sort of on an oblique angle. I'm chalking it up to just an old motor with archaic bearings. The motor won't draw any more than 6.5 amps in any position.

Yeah, I did try to gang the two 1 ohm, 50 watt resistors in parallel (provides .5 ohm, 100 watts) and that did spin the motor really well, but it also made the rheostat switch get even hotter too ..the coils within were glowing pretty good. Again, the hot switch concerns me.

After doing some more testing I found that the resistor(s) increased in value as the temperature went up. This definitely had an effect on the output voltage, etc. If I was pursuing this, perhaps I should be looking for a 100 watt version??

So the truck is a 1st series Chev, but the recirc heater is from a '51 GMC. I purchased it at a swap meet some years back. This was to replace the original small heater that had no fan.

I yes, always provide appropriate fuses for my accessories.

You'd think, huh. But I'm not happy with the dropping resistor arrangement I've experimented with.




Nice write-up and pics. However, my heater (GMC,HC-06-51) is quite different from yours.
Chevs of 40's: $60.75 not $50. And my motor shaft is 5/16". So, that motor landed in Canada will run me well over $100, plus new 12v resistor switch.

If I can't get any joy from using a simple voltage reduction kit, I may just order a spectrum of Chinese parts to experiment with. This could include bigger resistors, an electronic step down converter (as described earlier) or put together something like this, only make it easily adjustable with an extendable potentiometer for controlling the motor by omitting the pesky resistor switch altogether (ala PWM control):

http://www.hotrod.com/how-to/additi...nsive-voltage-drops-part-ii-transistors/

This still seems like a better more elegant solution to me ..other than replacing the motor and switch.

As was stated in the original post, I would just like to get some feedback from others who have had some success in employing these e-devices.

1. Switch is mounted where, and how it is, because of heat.
2. 6V and 6.5A is 39 Watts.
3. It's not a TelCom problem, it's a truck heater. Electrical, not electronics.
4. Understand you are looking for someone who has done it other than recommended. Not me, good luck.

There is nothing to experiment with. 6 volt heater switch WITH single quad lead 5 watt resistor built in right? Maybe you don't have an original switch then. The original switch has the resistors on it, a fuse holder and if you put your 12-6v drop before the switch, life is good other than the hot drop resistor. This isnt an AC motor so there isnt any mystery, just two single ohm resistors in series, (one after the other) with the junction between the two being your medium pickoff. If the resistor is broken or has been deteriorated, for 6 volts, use .8 ohm 5 watt resistors like GM did. For 12v, use 1 ohm 10 watt resistors. Use NO resistors if your switch is good because they are already on the switch!

This is part of the new article on 12 volt upgrades that pertain to this issue. Maybe it will help you in setting up a test bench to play with the various solutions you are thinking up. Nothing wrong with that! Keep us posted.

http://devestechnet.com/Home/Native12VUpgrade#heatersystem

Great article, Deve.

Until this afternoon, it could have applied to me...
as I was given an old "rusty" 12v blower motor from a '70's Bronco.
I test ran it before cutting off the mounting shroud, dismantled and thoroughly cleaned/serviced it, and attempted to put it back together.
But when taking it apart the bronze bushings came out with the armature.
Unless there is some sort of repair trick, I doubt the bushings can be put back into their sockets within the shell case -- there are little steel pawls that keep the bushings in place.
Too bad, as the modified motor casing might just have fit the heater core.

So if no-go, then it will be to my alternate plan: finding a more elegant way of dropping the voltage without the use of a power resistor.

Here's the heater assembly I'm up against:

http://s525.photobucket.com/user/my_pics48/slideshow/3100%20Truck

Everything that my website has on it about heaters applies, except keeping the 6v motor. Good luck! But, it would seem a 12v heater motor shouldnt be that hard to find since most heater motors for the past 30 years or more are 12v? Have fun in any case! And, please share with us the circuit you design for this using power transistors!

Well, Wayne started this thread a while back, to offer an
option to the dropping resistors that you can fry eggs on
under your dash or mounted in the duct work.
Ya'all gave him a real ration of sh!+ for his idea and every
reason under the sun why it was to complicated and wouldn't
work.
Using a Solid State voltage reducer sounded like a good idea
to me, so.....I invested $9.96 (free shipping) in a couple of
the DC-DC CC CV Buck Converter Step-down Power Supply Module
7-32V to 0.8-28V 12A Item# 221670461819 that he linked to.
Took a couiple of weeks to get them but they came in the
mail today.
I made a simple set up on the bench with a 6 volt Allstate
accessory heater, a 12 volt battery supply, a digital meter
and the voltage reducer. Connected them all up and watched
it run for about 15 minutes or long enough to run into town
for bread and milk this winter.
The ambient temperature today was 76° and that about where the
reducer ran for the full 15 minutes. No sign of over heating
and it is a simple matter of running 12v power to it and
running the 6v output to your load.

In my book, it's a winner and if.....I say If, I ever
converted an AD to 12v this would be my choice to reduce
the voltage to existing 6v devices.
http://www.pbase.com/dennygraham/image/161327441/large
http://www.pbase.com/dennygraham/image/161327442/large

As a side note, I had an AM radio playing next to it and there
was no RF interference.

Denny Graham
Sandwich, IL

I agree. All that matters is reducing the voltage before the original switch so you dont have a smoking switch. You can use transistors for it, or power resistors, but whatever you do, include the switch. Its not the switch thats the problem. Its the 5 watt quad resistor thats attached to it. If you decide to shunt half of your voltage into neverland. I would use a 12 volt motor so there is no reduction. Even new cars put the reducing resistors in the heaters air stream for low and medium settings. Whatever you do to get there is great. As long as you understand the ramifications of what can happen if things go wrong or installed improperly. Even my 1950 AM radio is converted to 12 volt filament tubes. Its just not that hard to go Native!

Well, after several weeks absent from working on my heater motor problem, the solution finally arrived in the mail. I had done some research into alternative ways of speed controlling DC motors and the following method seemed to be just the ticket, ala moderne.

But before I explain further, the decision was made to replace the original 6 volt blower motor with a 12 volt model from a ’75 Dodge. This was part of a 12 volt conversion upgrade. And I figured that because the truck lost its ‘originity’ some years back there was no need to further antagonize myself with the existing 6 volt motor. A simple Craigslist “wanted” ad produced several quick local hits, one of which was a perfect fit ($25).

Ok, so I had ordered a couple of pulse-width modulated [PWM] motor controllers — one as a spare. These were from an eBay (Chinese) vendor who was selling them at a very reasonable price: under US$6.00 each, including worldwide shipping!

When they arrived I was surprised how well made and just how small the devices really were: roughly 4”x2”x1.5”. A number of colored wires hung out of the crafted aluminum box, as well as a small tethered potentiometer used to adjust the speed.

Testing the device was a piece of cake and everything worked flawlessly: the heater motor spun up from barely moving, through its arc to full speed. This was accomplished by the variable resistor/pot. The unit didn’t even get lukewarm while it was handling the 4.5 amp motor draw. Installing it into the truck proved quite simple — easy to stash. By using a couple of flat washers I was also able to install the potentiometer into the original ½” dash hole formerly occupied by the old heater switch. It was even possible to then friction-fit the original knob over the new pot knob (which acted as a bushing).

Here is a link to a few photos taken of my buckshee test setup complete with heater fan, and new PWM controller:

http://s525.photobucket.com/user/my_pics48/slideshow/Truck%20heater

Note: Methinks if the decision instead was to have kept the original 6 volt motor, then perhaps using a high amperage 12~6 step down buck converter as Denny tested and reported on in an earlier post (and thanks for your kudos, Denny) and then controlling it all with a more appropriate lower-voltage input PWM controller.

My install was not to suggest the defacto way of controlling motor speed. Others here have addressed this matter quite competently.
But for me it was the most elegant — and cost effective — modern variant

I really like what you have done here 55! I have a few questions I hope you can answer..

1) Part numbers and sources for the Potentiometer and the Controller. Found it. Search Ebay for CCM5s Motor Control. I paid $7.18 shipped.

2)The Pot has to take up to 14 watts so did it get hot at all with the heater on LOW? The most amp draw you will see is less than 5 amps, but the power consumed is 10 watts or more.

VERY elegant solution I would like to bench test myself! Thank you for sharing that!

Well, thank you for the compliment, Deve.

I'm not entirely sure what you found. But for any others who are interested, check out eBay (or even Aliexpress) & apply search parameter "DC 9V 12V 24V 48V 60V 20A Motor Speed Controller Regulator Driver PWM 25KHz"
It should give you several units to choose from.
Be sure to get something where the circuit is enclosed in a box as it will act as protection, and as a heat sink in the event of higher draws.

This is a whole different ball game from what was discussed earlier on the topic -- the pot on this PWM device generates no heat at all in any of the speeds. The tiny pot only adjusts the bias of the internal ss devices. I would assume one can replace it with a physically larger pot but with same 100k value. This might make it easier to manipulate at the dash.

..I'm confident your bench test will also prove this out as a nifty solution.

As suggested previously, coupling this device with a 12~6v step-down buck converter on a 6 volt motor could also be an interesting experiment. It may save having to find a 12 volt motor replacement. But I'll leave that for someone else to post here

Can these motor controllers be used with an original 6v AD truck switch with a 12 volt motor? Could the original 6 volt AD switch be modified to take the place of the potentiometer? Where would you place the motor controller? Before or after the switch?

Tim

On the original switch, each resistor (there are two in series) is about .8 ohms. If we find the potentiometer is capable of .8 and 1.6 then we have our low and medium and we can use the switch just as it is. He gave us the hint however that is not the way it works because the pot is used to control solid state devices internal to the controller (probably at much higher ohm values). Nothing that is easy is worth doing. WE can figure out how to adapt it. If not Tim, there is always this:

http://devestechnet.com/Home/Native12VUpgrade#heatersystem

The 6 volt motor is another story. I have one coming for testing to find out.

Deve,

Again I am just trying to find an easier way to include my original 6v AD switch with the 12v motor so that it doesn't overheat on low and medium. Just wondering if this controller can be adapted to the original switch? I like the idea of the claim that no heat was produced.

Thanks again.

Tim

Oh me too Tim! This is very interesting. I have the parts on order and all of my heaters are 12 volt, so I can't wait to test this and adapt it to the switch. It is okay with me if someone beats me to it. We need to have an elegant way to do exactly that!

I got the 12 volt heater motor in and spent a few hours putting it in its new home. It is amazing how nice the 12v motor fits inside the 6v case. I have wanted to update the Heater Resto article for some time to include clearer instruction on how to do this. It's updated for now, but there is more to do. With a 12 volt motor you will never run into wiring problems or heat issues since everything is native 12 volts nothing to go sideways. New content starts about halfway down the page.

http://devestechnet.com/Home/HeaterRestore

I spent the day updating the document below to include the DC Motor Controller 551stseries was so gracious as to share with us.

I tested it on the bench and it looks like a very solid way to go however there is much more to this conversation than that! I have a larger potentiometer on order with an OFF Detent, and an aftermarket rotary switch (the old 6v kind for looks) that I plan on tearing down and using the knob and bracket so it looks decent for our purposes. Lots to it, but it's mostly all here:

http://devestechnet.com/Home/Native12VUpgrade#heatersystem

Scroll down until you get to it. This controller works for both 6 and 12v motors if installed correctly! (Thanks Wayne)

Don't know how you came out with your heater issues, but I wanted to ask you if you've considered using a Southwind heater? In your neck of the woods, it would make enough heat you'd be driving with the windows open. Just curious.
Tramp

If yer addressing me the OP, then I'm satisfied with the GM basic heater I have. Provides enough heat and keeps windows clear after warmup. (I also turn the no-draft windows a tad to help with any fogging.)

I live in the PNW and climate is mild. Also, don't drive the truck much in the Winter months.

Thanks for the contribution

Gas heaters, safe? Sure they're safe, just ask Rick Nelson
and the Stone Canyon Band.

dg

I am testing 100k pots with switch so we can take all power off the motor. The BIG question is going to be aesthetics. Our target audience for this mod would not be stockers, rather those who want to do a few tasteful tweaks to further enjoy their trucks.

This being the case, and also be the case that a Rotary switch is the best way to do this, what would the KNOB look like? Right now, you can get those aftermarket ones with the word HEAT on them. They even have a light built in. A 100K pot will have no light and good luck finding a knob that allows for a light, let alone the word HEAT. I want to do this right so I am hoping I can get some feedback here on how YOU would resolve this and please the majority. Anyone? Knob shaft is .25 or 6mm, preferred outside diameter is 1-3/8" or so.

Reason for the preferred rotary is that it gives us linear control of the fan rpm.

I found a really nice 100K Potentiometer with switch allowing for the click at the OFF point. With the Ohmite 5150 1-1/2" knob (same diameter as the aftermarket HEAT ones) this setup feels like you are tuning one of those high end Kenwood audio systems from the 70's. The knob is solid so its heavy which helps add to the solid feeling and the potentiometer is smooth all the way through its cycle. I tellya, Wayne hit this one out of the ballpark! The DC Motor Controller is THE answer for anyone upgrading their heater system. No heat is generated at all on any part of the system if you go to a 12v motor. It runs the 6v motor with reducer as well (just wire it up so the motor controller is outside of the reducers influence). Very sweet! Full linear RPM control.

http://devestechnet.com/Images/Projects/WarningSystem/WarningSystem0035lg.jpg

No backlight, but if you do not know where your heater knob is maybe you need a hammer instead. I DO want to find a backlit solution though.

Very nice work you made of your heater, Deve! Methinks that belongs more on a display wall than hidden away behind a truck's dash

Regarding some sort of ON-light for the heat:
howabout drilling a tiny hole in the mounting surface (or dash) just under the lip of the switch knob and install (glue) a mini-LED just as it pokes through the surface there? ..and connecting to the LED legs of course.
Or expand the switch mounting hole a tad and mount the LED just next to the securing nut?

Or (more complicated) install a mini-LED on the underside of the knob itself -- perhaps in its structural web -- and use a length of fine stranded wire to the PWM.
Alterative to the wire, perhaps a set of mini contact brushes??

Or a laser light clipped to the headliner and powered so it projects onto the knob when you call for heat.
Heck, even some newer lasers can clearly project words like "HEAT" or "LIGHT UP SOME WEED" anywhere you want them -- although 15 letters might take up way too much area.

Gee, so many ideas with so little time left...

What we really need Wayne is a super geek. Someone who has a 3D printer and can make us a knob with lighting inside and the word HEAT on the face. I would think that knob would sell all over the vintage world not just old trucks. The thing that struck me about the Ohmite 5150 that I got from Mouser was its completely solid so it is nice and heavy. You have some good ideas there! No surprise!

I have updated the Heater Switch section of the 12VUpgrade document to include how to make a bracket for the Potentiometer and knob. This DC Motor controller is THE way to go. No heat is generated, the linear knob gives you total RPM control, and there is nothing Cheap feeling about it. Works with 6 volt motor/reducer even better with 12v PM354 Motor.

http://devestechnet.com/Home/Native12VUpgrade#heatersystem
or
http://devestechnet.com/Home/Native12VUpgrade#SwitchBracket

I am not sure how everyone feels about lighting. Is no lights on your Heater control a big deal? If lights would be nice, there is room on the bracket to put an LED or two under the knob out of site as a backlight system, but then it would mean bringing power to that bracket which at the moment isn't part of it.