The Stovebolt Site Forums The Shop Area The Electrical Bay Installing led lights in instrument cluster.

All my dash lights in my 49 3100 quit working. I think it might be because they are 6 volt bulbs and the truck was changed to 12 volt. I was thinking of putting led bulbs in it. At least I hope the bulbs are just burned out. Haven't really dove into checking it in depth yet. Truck still has all old wiring under dash so could be some other problem. Thanks for any info on this issue. Grady.

Hi GradyB,

That's certainly a possibility. Have you checked brighter/dimmer function of the headlight switch? Sometimes the knob can be turned too far one direction or the other and it won't energize the dash bulb circuit. Those old switches can be found in really rough shape after 70 plus years. Jon G has a great headlight switch refurbishing thread to reference. Let us know what you find and you'll get plenty of help.

It could be that switch. It has never seemed to work correctly. I'll get it checked in a day or so.

I will try new 12 volt bulbs. Thanks.

I would agree with Bartamos that the answer is still NO. To add a bit of detail, I recommend against LEDs in places that were designed for incandescent bulbs for a couple reasons.

The first one is that the dimming curve for LEDs is very different from traditional bulbs. The dimmer circuit you have is a rheostat that adjusts the *voltage* down. The brightness of an LED is a function of the *current*. There is a relationship between them, but the brightness will be very non-linear as you adjust the dimmer. Also, once you get to the cutoff voltage for LEDs, they will just turn off instead of getting dimmer. Personally, I like the dash lights dimmer than I can usually get then on an incandescent dimmer.

The second reason is that LEDs and incandescent bulbs have very different light emissions patterns. When you put in LEDs, you will almost always end up with hot spots where you can see the "beam" coming out of the LED instead of a nice uniform glow. I say "almost" because you can buy specially made LEDs with a more uniform distribution, but they are still not quite right and cost $$$.

A third (and somewhat lesser) reason is that automotive LEDs tend to burn out much faster than incadescent bulbs. Unless you are spending literal dollars each, they are going to be "regulated" with a current limiting resistor and 90% of the time the value of that resistor assumes a 12V supply because autos use a "12V" system. Due to the fact that 12V automotive systems actually run +/-14V, those LEDs are being overdriven and burn out much faster than they should on paper.

All that said, I love me some good LED backlit gauges. But good LED backlit gauges are designed and build to take advantage of the LEDs quirks and to operate them within thier spec range.

Finally got to check further into problem. Changed light bulbs. No change. Seems the switch might be bad. Waiting for new one. All the wires under the dash are the original ones. Does anyone know if they make a harness for just under the dash? I can't seem to find just that. Most other wires on truck have bèen upgraded as it is 12 volt now. And also the fuse panel under the hood doesn't seem to have power at most fuses? Checked with volt meter. I would like to install turn signals, so should I just get a complete wire harness and redo everything? I'm not really much on electric wiring but figure if I take my time I can figure it out. Thanks.

It is one of the first things I do when I get one of these trucks. That old harness is brittle and falling apart. You would be doing yourself a huge favor.

If "no change" means that the only issue is dash lights not working, that is a very small issue. Easy to troubleshoot and does not require a harness. Be sure that is the only electrical issue, then we will help fix it.

It seems you are buying parts and have not done proper checking.

Don't know what you mean by other wires being "upgraded". Generally speaking, if 6V wires are OK, if insulation is not all dried out and cracked, they are just fine for 12V.

It could be you have the headlight knob rotated CCW. That may dim dash lights to almost off.

1. Who did the 12V conversion?
2. How did you know the dash lights were 6V bulbs? Were all the filaments burnt out?
3. How did you find 12V bulbs so fast without asking for a number?
4. Do you have the dash disassembled?

If you have any more trouble, as a person who is new to electrical, you need to ask before acting. We started out by advising to change to 12V bulbs and after you did that you moved on alone instead of reporting back. This is not usually a good way for a novice to work. But as you said, you can figure things out.

The switch has no stop points. It just goes round and round. Figured that wasn't right that's why I ordered a new one. Is there something else to.check while I wait for new switch? I've not taken anything apart yet.

If the switch knob to dim the instrument lights just goes round and round, the switch is toast. The rheostat is supposed to rotate maybe 300 degrees between stops, so the contact is probably broken, meaning there's NO voltage going out to the instrument lights.
I think you're on the right track replacing the switch.

Normally you would drop the headlight switch and let it hang. Then check to see if the dash light terminal had 12V as a first step. Maybe the new switch will be the ticket. If you have problems after install, report them. Sometimes an aftermarket headlight switch is slightly different as to wiring. Did you buy the 12V version?

As for anything else to check, you only mention one other issue. The fuse block on firewall. You would use an ice pick voltage tester for that. You would test input side of fuse and output side of fuse with ignition switch off and ignition switch on. Report results and report what each fuse does and what item it is protecting.

You are not answering my questions from my last post.

To answer your other questions:

With mechanical gauges, there are not many wires to need to buy a "dash harness".
Adding turn signals may require socket changes and a few wires. Dual filament bulbs are required which need dual filament sockets.
The decision to buy a whole new harness depends on the condition of wires. Ratty or decent. Stiff or flexible. Loose terminals on the ends or tight. There are some very good advantages to a new harness.

Ok just checked The fuse panel under hood. No power to top 4 fuses with ignition switch on or off. Bottom fuse had power with switch on or off. The second and fourth go to headlight and power when lights are turned on. Third has power when parking lights are on. Don't know what first, top, fuse goes to.

Top/first fuse: Hi beam........power depends on dimmer switch and H/L switch
Second: Lo beam.....power depends on dimmer switch and H/L switch
Third: Park lights......power depends on H/L switch
forth: Tail lights......power depends on H/L switch
Fifth: Stop.....power depends on brake switch/pedal depressed
Sixth: Horn........hot all the time so horn can always honk

Looks like all are working correctly.

Ok they all work ok but there are only 5 fuses on mine? My horn does work. I order to drop light switch I should disconnect the power right?

Grady, I was still typing, go back and read. Can you figure out which fuse is missing?...or two wires on one fuse?

Headlight drop: Disconnect the battery negative cable. Take switch loose and see if it has enough wire length to hang and you can get at it. May have to unscramble wires under there. Once all terminals on H/L switch are safe from touching metal dash, attach battery cable and test switch.

It's good to have the H/L switch dropped and still wired so as to transfer wires to new switch one at a time. (with battery cable disconnected)

Got switch dropped. Some of wire to instrument lights are missing the coating. There's bare spots. Light bulbs I looked at aren't blown but have different numbers on them. 53 and 57 and 1445. What should they be?

Wires sound like they need replaced. Especially if other wires are similar. May be time for a harness. Not my call.

The bulbs are all 12V. The 57 is twice the wattage as the other two and it's globe is bigger. The bases are all the same. They are OK if globe fits panel hole.

Any suggestions as to what harness would be best? And should I get one with the turn signal hook up? Question you asked earlier the truck was wired when I bought it 6 years ago. Not everything was redone. So I guess now it's up to me!😜

You want a harness with a prewired fuse panel. 12 circuit will be plenty. EZ wire or Speedway universal harness or equivalent. $170 -$220. All are about the same quality. All have instructions. They all support turn signals. They support alternator or generator. See what you think.

The EZ wire 12 Circuit Standard has the larger fuse panel. I guess the mini version is OK too. (instructions are very primitive)

The Speedway is also a good harness. (good instructions) They also sell a turn signal switch $36. Click..................and Click The order will be free ship.

The install won't be over your head with help. There are several things you can eliminate while doing the new harness. The new harness will take some soldering/crimping and crawling.

Ok. I will get one ordered and ask for help when it gets here and I get time to do it. Thanks for all the information. I will be back.

I added and subtracted info just now. Better review.

Hello again. Received the wire harness from Speedway and a new light switch. I am going to get at this soon but have a few questions.
1. Will I remove the original headlight fuse panel or just hook up to it? I would like to keep it in as the truck is mostly all stock.
2. I think I will have to get new sockets and bulbs for turn signal installation.
3. Should I remove all old wires from truck first?
This looks intimidating, but I will take my time and ask questions if I get stuck. Am going to start on in next few days. Thanks, Grady.

If it was my truck, I would make a wiring diagram of what I have now and compare with the original Chevy/GMC diagram.
I would understand what I have before removing anything. Take pictures.

Many replacement wiring harnesses "modernize" and are not the same as original.
Learn and understand the differences before you start.
Example:
The kit may be designed for a newer GM steering column which has a new plug and you may have to fabricate or purchase an adapter plug.
The kit may not have the instructions you need to adapt your existing turn signal circuit (there were/are many different add-on turn signal kits).
Most likely you will need to make a turn signal wiring diagram of what you have, and figure out how to adapt it, before you begin.
The manufacturer, of the new wiring harness, may sell a turn signal kit that is designed to work with your new wiring harness.

Just in case, if you have changed from 6V to 12V and retained the original fuel gauge then you either need a voltage dropping resistor, regulator or buy a new 12V gauge.

1. You can leave it mounted but you will not hook up to it. It will not be wired to anything.
2. Yes
3. Yes

What is the part number of the new harness from Speedway?

910-64017. There are a lot of wires I don't think I will be needimg. I guess they can just be cut off? I will take pictures of things before I remove them.

No, you don't want to cut any wires except to get the correct lengths. Any unused circuits/wires will be looped and tied up under the dash. You probably want to mount that fuse box upper left of your left foot in the cab. But low enough to get at fuses. Engine, front light and rear light harness branches will go thru the firewall in 1,2 or 3 places depending. the dash and cab branches stay inside cab. Install dual sockets front and rear first. Take out old harness sort of in one piece, here and there.

I would disagree with Bartamos on one point: question 3.

It can be very helpful to have the existing wiring in place while you are figuring out the routing for the new harness. All of the existing wiring should come out, but not necessarily "first".

And definitely don't cut off the "extra" wires. Make sure the ends are covered so they can't short against anything and/or remove the fuses powering them and zip tie them out of the way for the eventuality that you want them in the future. You don't want to discover 3/4 of the way through your project that you cut off a wire you needed and have to put it back.

For sealing the ends of wires, I like to fold the end over into a J and put a pieceof heat shrink over it to fully cover the end. I find the heat shrink is less likely to accidently get pulled off that way than if I just put it over the end of the wire.

Follow bartamos's and Fibonachu's excellent advice : "you don't want to cut any wires" & "definitely don't cut off the "extra" wires"

There is not a lot to worry about how it was wired or routed. You will more or less end up about the same look.
Also I recommend an alternator and a voltmeter if that is possible regarding your desire for "original". Those items are for simplicity and reliability and are especially adapted to 12V systems.
I have a whole bunch of info/advice/opinion and you will need lots of help. A complete install takes a lot of posts. Kind of difficult to get a whole rewire job done from a forum. Many different answers/opinions and takes days to answer sometimes. Lots of helpful folks here however.

Been studying and looking at the wiring and decided to not use the harness from speedway. The reason being as I didn't want to have all the extra wires coiled up under the dash. As long as I own the truck it will be as close to stock as I can keep it. I have a harness from chevys of the 40s. It's specific for my 49. Was looking at it tonight and have a good idea where everything goes. Only concern is that the wires in the truck going to headlights are much heavier than in the harness. They are all a blue color so I think they may have been changed before I got the truck. Should I be concerned about the difference in wire size? I will be getting at this project very soon. Still a little scared. Thanks for all the info, Grady.

If the harness is "specific for 49", there is nothing to worry about. Colors not mentioned in 1949. Colors/tracers/cross tracers showed up in 1950, but flaky. The modern colors started to show up in 53.

Commentary:
Chevs of the 40's has two harness for 49. One @ $187 and one at $815. You don't accomplish anything meaningful by buying a "specific" harness except to spend a lot of money for nothing. The $815 is cloth covered or cloth loomed wire and is outrageous in price. Unknown insulation quality, abrasion resistance, heat resistance, environmental exposure testing. The $187 is uncovered modern plastic wire, same as a Speedway for example. Yes the terminals are crimped on and the wire lengths are correct. Nothing special about that. That doesn't create "original".

When "restoring" our old trucks, many say they want to keep it "original". There are many folks who start thinking about safety in todays world, highways, speeds, thousands of other fast drivers, dangers of getting stuck on the road/reliability. Original is carried TOO FAR unless you are going to use the truck on a limited basis.
Brakes, tires, steering, differential ratios and WIRING were all designed for a 30's, 40's and 50's world. Designed with the available knowledge and materials. All of the aforementioned systems need upgraded and do not really affect any normal conception of original. (the ratios can be an exception if performance is OK). The addition of turn signals is mandatory. Repeating some of the wiring "mistakes" of those eras is not prudent. I see that Chevs of the 40's used some fork tongue terminals in their harnesses, so as to be "original". An example of continuing a bad idea.

An upgraded harness is better in many ways than what the inexperienced electrical engineers did/used. There are so few wires in old trucks that with a little help, anyone can wire them. No soldering is necessary, just good crimping and some shrink sleeve to attach the necessary ring tongue terminals and/or connector contacts. Cut the length, route and tie up.
In the end, of course, it's up to the individual. But at least be aware of the aspects of "original syndrome".

Well it's been awhile but I am started on the rewire of my 49. Things are going pretty well. Taking my time reading instructions, hooking things up and rereading . Just to make sure it's right. I'm going towards headlights and when taking out old wiring there is a relay, I think, AR-501 12 volt 2x 15 amp where the wires went to then to headlights and fog lights. Fog lights were on their own separate switch. There was also an extra 10 Amp fuse wired into the relay and lights. Is this something I need to reincorporate into system?

What about using LEDs in turn signals on a 12 volt system.

Decided to just keep everything as it was.

Except adding turn signals.

Yes

Other priorities have taken me away from the rewire for a bit, but back at it again. Just what does the relay do? I would like to understand how it works. Electric wiring was never a good subject with me but I am getting more comfortable with it as this learning lets me know i haven't lost all my mind at this age in my life.

A relay is just a switch. In your case you have the original headlight switch and some sort of fog light switch. Either original or aftermarket. Some folks think these switch's contacts/internals can not handle being converted to 12V or handle certain added loads. Therefore they install a relay. A relay is a switch that can handle larger loads. It is operated by the headlight switch and/or the fog switch. It only takes a small current to activate it. The small current powers a small coil which closes the switch. When the switch closes, larger more capable contacts close and finish supplying power to the lamps.
The only thing the headlight or fog light switch does is operate the relay. Your relay is a modern case 30A style. The older horn relays were a tin can style.
Many of the older headlight switches are 30A fuse protected, so it seems they were made to handle the same load as a relay. That is a debate we have had before. They do have big contacts built for 6V currents.
Converting a 6V system to a 12V system does not require a new headlight switch or relays. There is no electrical difference between the 6V and the 12V headlight switch they sell you at vendors.

Thanks. I'm figuring it out. It's going slow but will be worth it when completed.