The Stovebolt Site Forums The Shop Area The Electrical Bay Is "discharging" a problem??

I continue to improve the wiring and functionality of my 58 Suburban. I have the original lights (quad headlights, front markers and rear tail lights) and a set of amber fog lights that were on the truck when I bought it but not hooked up. I wired them in yesterday. I have to aim them better, but they work great. Today I installed a new Tach to replace the HF piece of junk that I bought, as well as a cig lighter/power port.

When I drive the truck with nothing turned on the ammeter reads dead center between D and C. When I turn on the headlights its dips a little towards D. On high beams it dips further. I went out for a test drive this evening. I had turned on the high beams, the fog lights and I plugged my GPS into the power port to test my speedo for accuracy. With all that on the ammeter was down to "a quarter tank" on the discharge side.

Unlike the oil pressure gauge which climbs in relation to engine RPM, the ammeter never goes above dead center.

Is that bad? I guess I don't fully understand the function and data displayed by the ammeter. Does the low reading just mean I'm using a lot of juice or am I really discharging the battery? Is there a way to use my multimeter to see what is going on when all the accessories are turned on?

I have been very careful to use in-line fuses on all the extras I have installed in the truck. I don't think I'm going to start any fires or anything.

you're probably discharging the battery if the meter is good and not hooked up backwards - when you first start the truck you should see the ammeter dip toward discharge, and as the engine starts it should move back to neutral, faster or slower depending on how long you cranked, so how much you ran down the battery - when you first turn something on like headlights you should see a flick toward discharge, then immediate return to 'neutral' .... the ammeter shows how much juice is being sent to the battery or being taken from it, not how much the accessories are using at the moment, the electrical items should be getting supplied by the generator

it may be that your generator or alternator isn't putting out much or anything or the regulator is stuck - new charging device? if it's stock, did you polarize the regulator/generator when you installed them? the way to investigate with a meter is to check battery voltage under all the different conditions, everything off, running, and then with some electrical things on

Bill

Bill;

That's what I was thinking. Either the altenator isn't putting out enough juice or I have a short somewhere. The truck starts right up so I don't see much movement at startup. As electrical items are turned on, the gauge dips towards discharge and just never recovers. The more I turn on, the lower it dips. Then it just stays there.

As far as I know, it is the original unit. The motor is not original. I believe it is a 78-79 250.

How would I polarize the altenator? Am I supposed to polarize it or is that a mistake? To check the battery voltage, should I put the positive lead right on the battery post and the other on a ground? Maybe I could then compare readings from there with readings taken at the altenator.

Obviously electical issues are my most pressing and difficult to wrap my mind around.

Larry:
Some Ideas
- To check for polarity of the ammeter wiring: just disconnect the coil output wire to the distributor, so the engine won't start. Then turn the engine over. You should see a pretty significant negative discharge during that time.
- Was everything normal before you made the latest round of modifications? If so you may want to consider the old rule "check the last thing you did." You may have inadvertently disconnected a wire or mis-wired.
- I'm not aware of the need to polarize an alternator. I never have.
don

Don;

Thanks for the tip. No, everything was not normal before I started my upgrades. The needle always dipped toward discharge when I would turn on the headlights, especially on high beam. I didn't really think much of it until the other night when the needle went so low and never came back up. I don't think I caused the problem.

On a related note: what is the function of the voltage regulator mounted on the firewall? If my alternator is internally requlated, is the firewall voltage regulator not needed? I have a new one in the box that I bought sometime in the last few months. Maybe I'll swap it out tonight and see if that changes anything. If I have time this evening I'll go out to the garage and run the truck with varying degrees of electric items turned on and just messure voltage everywhere that makes sense.

More to follow...

you may have either an internal or external regulated alternator, if it still has the original generator style regulator [3 terminals], with an internally regulated alternator, the regulator is just a junction box, if you have an externally regulated alternator with the correct regulator [4 terminals], it controls the charging activity and could be defective

you might also put a charger on the battery and see if it's been run down after your fiddling or if still has a good state of charge

Bill

" Either the altenator isn't putting out enough juice or I have a short somewhere."

One of the first things to learn about electrical troubleshooting is 'short' means a short circuit to ground. 'There is some electrical problem' does not equal 'short'. If you had a short you would have hot wires and insulation burning.

As Bill stated, you need to ID what alternator you have.

Cletis;

Hooah. Point taken. Correct terminology is important.

I'll take a look at it tonight and see if I can get a picture to upload.

I am happy to report that there is no smoke or fire. All seems well accept for the fact that I have a discharge problem.

Some quality time in the garage with the multi-meter and the wiring diagram/assembly manual will serve me well I think.

Larry,
If the alternator is a 78/79 it would be internally regulated. You would not use the regulator in the firewall. Look at the plug that plugs into the alt., if the plug looks like this (--) it is an internal regulator. If it looks like this (II) it is an older model and would use an external regulator. Why not just take it off and get it checked, most parts places check for free. It's only a couple of bolts to remove it,and if you're not smelling anything burning it's probably bad and will need to be replaced anyway.

Update:

I crawled around on the truck and got the following info on the altenator. Delco Remy 1102473 55A. I assume that is a 55 amp altenator. It has a 2 prong connector (--)on the side with a heavy red wire and a smaller black wire. There is also a bolt on the back with a heavy red wire on it. I'm not positive on the color of the wire on the bolt. I'm partly color blind so picking out colors (especially red/green) in the low light of a drop light is challenging. Anyway, I'm pretty sure it was red.

First I disconnected the power to the distributor and cranked the truck for 5-8 seconds. Absolutely no movement on the ammeter.

I then decided to check the voltage at the following locations:
a. on the battery, one terminal to the other
b. on the battery, positive terminal to chassis ground.
c. on the alternator: bolt post to chassis ground
d. Alternator: red wire on connector to chassis ground
e. firewall mounted voltage regulator "batt" connector to chassis ground.

I started with the vehicle off with no electrical components turned on. This was after the initial no-spark crank to check if the ammeter moved, so there may have been a slight drain on the battery to begin with. The following are the results:
a. 12.40
b. 12.46
c. 12.48
d. 12.48
e. 12.48

Next I started the truck (again no movement of the gauge during crank/startup) and ran it with no electrical components on. Gauge held steady at TDC the whole time.
a. 14.62
b. 14.70
c. 14.82
d. 14.77
e. 14.75

I than turned on the high beam lights, the and the fog lights. I didn't think to turn on the electric wipers. As I turned on the lights the ammeter dipped toward discharge. When everything was on, the needle was down around 1/4 tank towards discharge. It moved down incrementally as the electric components were turned on. It stayed steady and didn't recover at all until I powered off the electrical items. When everything was powered off the ammeter immediately returned to TDC. The voltage readings were:
a. 14.52
b. 14.53
c. 14.55
d. 14.65
e. 14.20

Finally I shut the truck off after having run it for 15-20 minutes with varying electrical loads on it. The final readings were:
a. 13.00
b. 12.97
c. 12.92
d. 12.92
e. 12.91

So what does all that mean?? The pre-start volts looked good and were consistent across the board. During operation the voltage remained constant on all readings regardless of the load on the system. Following a 20 minute run the shut down volts were slightly higher than the pre-start.

My deduction is that there may be an issue in the gauge. Am I tracking???

What's next??

A 55 amp alternator is a little low to charge battery, power high beam headlights, fog lights and wipers. Voltage and amperage are different. Your amp guage is proberly correct in showing you a discharge with all of that load. An in line amperage draw test is your next step to prove you need a larger amp alternator. Most newer cars run 105 plus amp alternator to keep up.

Mike;

Ok. I'm tracking. How do I do an in-line amperage draw test?

Should I just buy a larger amp alternator and call it a day?? Is there any danger to the truck by getting a larger (say 100amp) alternator? I'm not going to melt down the wiring am I? I don't think so, but don't want to make any more ignorant assumptions.

you have a 10SI internally regulated alt .... 55 amps is fine, the original 30 and 35 amp generators ran the same equipment plus more, if adding various modern appliances you might want to go to 65 amp or even a 12SI, 78 amp, but 94 or 105 amp alternators are unnecessarily expensive and scarcer, that's what I put on my RV bus because it'll have 2 start batteries and lots of other draw

reading a bunch there at Mad Electrical might help you understand the system better Larry, I'd say it sounds like the system is working, but something is wired wrong to cause the gauge to read the wrong place in the circuit, need to track the wiring

Bill

Bill;

The MAD Electrical site is awesome. I'll be spending a bunch of time there getting smart on electrical. I assume they have an article on how to see how many amps are being drawn by the system during operation. I'm just curious to see how hard my 55 amp alternator is working to run what I have hooked up. It will be good to know as I make plans for future add-ons.

Thanks for all the help!

Larry,
With the alternator putting out 14.5 volts on a load it is working as it should. What kind of gauge are you using, The original factory or an aftermarket gauge. I'm wodering if you have the wires on the gauge reversed.

Tommy;

As far as I can tell it is the original gauge. Based on Bill's comments and the fact the engine has been swapped, the current theory is that when the new engine and harness were installed, the wiring was run bypassing the ammeter. It is capturing the discharge going throught the dash harness to the electric components but is not capturing the charging being done by the alternator.

I plan to unhook the battery and all the wires from the starter and alternator and then running continuity checks to see where the wires are going. If theory holds true I will find that the wiring from the alternator skips the ammeter and sends the charge straight to the battery. I may have to re-direct/reattach the alternator wiring through the ammeter to the starter/battery.

More to follow when I get some time to really play with the wiring.

Bottom line is I full a lot more comfortable driving the truck. I was afraid it was just going to go belly up out on the road sometime. I am charging the battery and maintaining juice in the system, I just can't see it properly on the gauge.