Volt Gauge Sky High

[GLHS592]

I took the Shelby Charger out the other day after I got the dash back in the car and noticed that the volt gauge was reading very high. I double checked the plugs on the back of the cluster and they are plugged in correctly. Of course, they only plug in one way. The car has a SDS stand alone fuel injection system with a carb'ed L-body voltage regulator. All the wiring looks good. Would this be a sign of a bad voltage regulator?

[GLHSKEN]

Kevin,

My 82 charger 2.2 would ped sky high (external reg) looked like I had halogen headlights (back in 1984.. hell I don't think they were even out!!!) Took it in to be tested. Tested fine.. ran it again, same thing... It was intermittent. Brought it back to be tested.. Tested fine, I said "shake it" well, it went balistic. A new reg solved it.

[8valves]

I took the Shelby Charger out the other day after I got the dash back in the car and noticed that the volt gauge was reading very high. I double checked the plugs on the back of the cluster and they are plugged in correctly. Of course, they only plug in one way. The car has a SDS stand alone fuel injection system with a carb'ed L-body voltage regulator. All the wiring looks good. Would this be a sign of a bad voltage regulator?

Take a multi meter and test the check the posts of the battery while the vehicle is idling. With the car off it should be around 12.5v (make sure it is checked after the car has been running since it's in storage, but give it a minute for any "ghost voltage" to wear off) With the car running depending on the condition of the charging system your posts should read 13.5 to 14.5 volts I believe. For your gauge to be pegged or sky high it would probably have to be out of that range by quite a bit.

Wouldn't you more lean to the idea that it was something that happened with the dash going in/out a sin a gauge hookup, even though you checked them once, since it was fine before hand. Is it a different gauge cluster and the gauge is whacked? Just throwing out some options. I'm a litle rusty on my electrical skills, it's been a while since I've had to deal with them.

Aaron Miller

BTW- the check showed up a day or so ago Kevin, thanks!

[GLHS592]

I would have tried the multi meter, but it's in my tool box across town. :( I'm using the same gauge cluster. I'm not sure if the voltage was doing this before the dash swap because I've not driven the car much since SDAC-15. I last had the car out before Halloween. I don't remember the volt gauge being pegged. The voltage regulator is only about a year old.

Another thing I noticed is the problem with my dim driver's side headlight and non working parking light went away. Could this be related?

[8valves]

Maybe. If those two items use the same feed wire and has some sort of resistance not allowing normal voltage to A) light the headlight properly and (B) get the parking light to come on...

And now that you have monster voltage being supplied it can push through this resistance and give it enough juice...

Just a random idea though.

That would make everything make sense, and would point back to you having a bad regulator. Or so it would seem... Your car is well done enough that I don't see it being a random old wire issue or something along those lines.

Aaron Miller

[WVRampage]

sound like a bad regulator.

[jckrieger]

Make sure all your grounds are good, especially from the regulator to the battery. My old 79 Ramcharger (same regulator) was overcharging due to some rust between the regulator and the firewall.

[GLHS592]

I'm assuming Autozone can check a voltage regulator. I will check all the wiring while I'm at it.

[GLHS592]

I started the car up tonight. This is odd. The voltage gauge was normal. Here's the catch. When the gauge is normal, the driver's side headlight is dim and the driver's side parking light doesn't come on. When the gauge is sky high, the lights are normal. What in the world?

[GLHS592]

Does this sound like a ground problem or a voltage reg. problem?

[GLHS592]

Anybody? Help! Please! I suck at electrical.

:)

[GLHS592]

I fooled around with the car today. I fixed the headlight and parking light problem. The headlight was a bad ground and the parking light was a loose filament in the light bulb.

The voltage regulator shows normal when the engine is at idle. Any rpm over idle causes the voltage gauge to go sky high again. I'm going to have the voltage regulator checked out at Auto Zone.

[JDAWG]

sound like voltage reg, or poss bad fusible like or wiring, got a spare power module or logic module to swap?

[GLHS592]

I don't have a logic module or power module anymore. I have a standalone ECM with an external voltage regulator. The wiring looks good.

[GLHS592]

I swapped in a brand new voltage regulator. It is doing the same thing. I tested the volts at the battery. At idle, it is showing around 12 volts. When you rev the motor, it shows anywhere between 12 volts and 19 volts. I'm guessing it's a bad alternator. HELP!!

[Tony Hanna]

I can't see how the alternator could be your problem. If I remember correctly (and it's been awhile) the voltage regulator controls the alternators output by varying the power supplied to the alternator's field windings. Taking that into account, your symptoms point more toward a regulator/wiring problem resulting in too much power to the fields which would cause the alternator to overcharge. A quick way to test this would be to unhook the field wire. With the car running, it shouldn't charge at all. Maybe I'm wrong, but that's all I can come up with.

[GLHS592]

The wiring was brand new last year and I've swapped in a new voltage regulator. I just can't see it being anything other than the alternator.

Field wire? Are you talking about the wire on the alternator or voltage regulator?

[Tony Hanna]

The field wire should be running from the alternator to the regulator. If there are two of them one will run to the regulator and one will ground (I think).
I'm getting in a bit over my head here because I understand the general theory, but I don't have any practical experience with the Chrysler setup. I've been lucky enough so far not to have any problems out of the stock setup.
With that said though, in an externally regulated setup, there shouldn't be any way for the alternator to overcharge unless it's a fault of the regulator.
The only possibility I can see and it's extremely remote is that something shorted internally causing the alternator to get a full 12 volts at the field constantly.
I wish I could be more help.

[DeckSetter]

Has the high voltage fried anything else yet?

My 280ZX needed an alternator when I got it. It was charging WAY high anywhere off idle, and it fried the ignition module in the distributor. New alternator, problem solved. They told me when it charges too high the diode pattern is bad. What that means, I have no idea...

I've never had to mess with an external voltage regulator, how does that wire in? Does it wire between your alternator and battery or between the battery and accessories? If it's between the battery and accessories and the voltmeter reads straight off the battery, your alternator is probably shot and overcharging your battery while your regulator is keeping everything else happy.

[GLHS592]

Nothing has fried. I'd have to ask Kevin Davis how it's wired in because he wired it for me.

[87csx2.4]

With that said though, in an externally regulated setup, there shouldn't be any way for the alternator to overcharge unless it's a fault of the regulator.
Exactly,its got to be the reg.I bought 2 the last time and 1 was bad out of the box.

[GLHS592]

Kevin, do you have a known working regulator I can try? I just don't think that's the problem.

[Tony Hanna]

Kevin,
Do you have a spare alternator you could swap on?
I'll be really surprised if that turns out to be the cause of the problem but if you have one, then you're not out anything but a little time to try it.
How does that saying go? When you've exhausted every other possibility, the remaining possibility no matter how improbable has to be correct.
This sounds like it's turning into one of those head scratchers where you go through everything without finding the problem and then one day you figure out the regulator body isn't getting a good ground or something goofy like that and fix it.

[87csx2.4]

Kevin, do you have a known working regulator I can try? I just don't think that's the problem.Ive got 2 or 3 alternators and a voltage reg.come on by and get them.

[Phreakish]

its your alternator, trust me. I had this SAME issue with my charger last year, you can read the drama on TD.com

Anyhow, there was somehow a short ONLY at higher rpm than idle that would full field the alt and cause an overcharge... The alt tested fine 8 times, and the field always read fine. I finally hooked a DMM to the field and revved the engine - direct short to ground at rpm... go figure. I even replaced brushes, cleaned the comms, rewired the field terminals, still had to replace the alt... sigh.

[GLHS592]

I was thinking of upgrading my alternator anyway. Kevin, how much for one of your alternators?

[GLHS592]

I finally got it fixed. As it turns out, it was easy. I was told it didn't matter which wire went to the alternator and which went to the power source. It does. I switched the wires and the multi-meter shows just under 12 volts at idle and any higher rpm.

[Tony Hanna]

Should charge a touch higher than that shouldn't it?
I usually look for 13.8-14.5

[GLHSKEN]

Glad it's working. I HATE elec problems... I'd rather pop a piston than track them down.

[BadAssPerformance]

lol, I hate electrical problems too but I don't know if I'd go that far ;)

[GLHSKEN]

You don't know me and wirecutters.... let alone the soldering iron. ;) When that happens it's pick-up phone and dial either Warren or James!!!

[Tony Hanna]

I always rather enjoyed working on electrical problems. Some of them can present a pretty interesting challange.

[GLHS592]

Should charge a touch higher than that shouldn't it?
I usually look for 13.8-14.5

Would an underdrive pulley affect the voltage?

[Tony Hanna]

Would an underdrive pulley affect the voltage?

Since it spins the alternator slower, it may affect it at low rpms. Have someone hold the engine at ~ 2500 rpm and check it again. If everything is right, you should see 13.8-14.5 at the battery terminals. I know some people don't like underdrive setups because of this (charging problems at lower rpms) but I can't see it being a problem except in a situation where a vehicle spends alot of time at idle. I sure wouldn't want an underdrive setup on a taxi...:nod: For a driver or race car, it should work fine as long as the battery has enough reserve capacity to take up the slack until the rpms come up.
HTH,

[GLHS592]

I checked it both at idle and at rev. It showed just under 12 volts the whole time. The voltage stayed exactly the same. I wonder if the voltage reg. is supposed to hold the idle voltage. I've not had any problems with it. I don't have too many things in the car that would draw voltage. I have no heater or radio.

[Tony Hanna]

In that case, it sounds to me like it's not charging. The reg should hold the alternator's output between 13.8-14.5. It may not be able to at idle due to the underdrive, but it definately should as the rpms come up. Just out of curiosity is there any difference in the voltage reading between when the engine is running and when it's off?

[GLHS592]

It could be a bad voltage reg. I will check the voltage of the battery with the engine not running next time I see the car.

[MiniMopar]

The way the stock charging system works is that one field terminal is connected to 12V (often a black wire with dark green stripe...the ASD relay output, or a dark blue wire...the ignition key output). The other (dark green) goes to the power module, which drives the wire towards ground when it needs to generate more charging current.

The external regulators work the same way. One terminal should be connected to the ignition key power source and the other to the regulator. The other terminal of the regulator will also be the same 12V feed (dark blue wire). This is how the regulator gets internal power and also how it senses the current charging voltage. The regulator gets it's ground from the chassis.

Now it sounds like your wiring is all hackified, since you say that you are not using the stock electronics, so the wire colors may not apply. When it was overcharging before, it was getting full-fielded (full 12V across the field terminals). Now you say you swapped the field wires and it isn't charging at all. Sounds like one of the alternator field terminals is shorted to ground. Did you blow any fuses this last time?

[GLHS592]

Now it sounds like your wiring is all hackified, since you say that you are not using the stock electronics, so the wire colors may not apply.

I'll assure you that that isn't the case. Nothing on this car is "hackified" at all.


When it was overcharging before, it was getting full-fielded (full 12V across the field terminals). Now you say you swapped the field wires and it isn't charging at all. Sounds like one of the alternator field terminals is shorted to ground. Did you blow any fuses this last time?

It was overcharging before. Now, it is showing just under 12 volts at idle and any engine rpm. The car runs and starts every time. I haven't blown any fuses in a while. Even when it was overcharging. Also, when the alternator was overcharging, it showed just under 12 volts at idle.

[MiniMopar]

I'll assure you that that isn't the case. Nothing on this car is "hackified" at all.

Sorry, all I meant was that the wire colors I mentioned may not apply to you if it has been completely rewired. I did not mean in imply that your wiring was a hack job. :thumb:


It was overcharging before. Now, it is showing just under 12 volts at idle and any engine rpm. The car runs and starts every time. I haven't blown any fuses in a while.

Yeah, you are probably not charging anymore at all. Without poking around with a voltmeter, all I can say it to try to swap things. The alternator would be the next suspect. You can experiment, if you wish, and disconnect the field wires that you have now and try to apply 12V across the terminals while it is running (be careful). If the voltage doesn't go way up with some throttle, then something is up with the alt, probably.


Even when it was overcharging. Also, when the alternator was overcharging, it showed just under 12 volts at idle.

Well, that's not all that unusual. The charging systems on these cars tend to struggle quite a bit at idle, especially when there are other electrical loads like headlights or if an underdrive pulley is being used. The ECU will full-field the alt, but it can't always keep up. If the voltage went through the roof when you blipped the throttle, then I think it is safe to say that there was a short and the alt was full-fielding all of the time.

How much of the front engine harness is original? There is a large ground splice inside the harness around where the oil pressure sensor is. I've seen the splice get toasted, which makes the alt go nutty.

[GLHS592]

Sorry, all I meant was that the wire colors I mentioned may not apply to you if it has been completely rewired. I did not mean in imply that your wiring was a hack job. :thumb:

OK. The car hasn't been completely rewired. The SDS splices into the factory harness.




Yeah, you are probably not charging anymore at all. Without poking around with a voltmeter, all I can say it to try to swap things. The alternator would be the next suspect. You can experiment, if you wish, and disconnect the field wires that you have now and try to apply 12V across the terminals while it is running (be careful). If the voltage doesn't go way up with some throttle, then something is up with the alt, probably.

The voltage I'm getting is at the battery, so I'd assume it is charging at least < 12 volts.


How much of the front engine harness is original? There is a large ground splice inside the harness around where the oil pressure sensor is. I've seen the splice get toasted, which makes the alt go nutty.

The complete front engine harness in all intact. I will check more grounds when I get back to my parents' house.

[Phreakish]

its still your alternator...

Like I said, same issue with me. It doesnt' matter at all what wires go where on the field (so long as they ARE field wires). If there is a short in your field, it can cause the voltage to drop below 12 (you should always have at least 12.5v at idle, and 13.5-14 otherwise).

The alternator wont test bad tho, swap in another and see if it goes away... when it does, ya owe me a beer ;) lmao.

When I had the problem, I could swear that the alt was the last issue it could be, but as soon as I swapped it, bingo - problem solved (had to replace some fusible links with real fuses tho! damn short caused massive power draw thru the power feed to the PM and fried part of the fusible harness).

[GLHS592]

I'm going to try my other voltage regulator first. Then, I'll try the alternator. If you're right, I'll work out some sort of payment. :)

[Phreakish]

lmao - Yeah, I carry a spare... everything... in the trunk. The friend riding with me when it happened in phoenix (145 miles from home) laughed his --- off when I pulled out a spare... COMPUTER for the car, hah (since I still have the lm/pm). But if you're interested, you can read the saga at td.com:

http://www.turbododge.com/forums/showthread.php?t=79875&highlight=alternator

[GLHS592]

I finally got the chance to take the alternator to get it checked out. It was shot. A new one will be here Tuesday. $40 with a core at O'Reily Auto Parts.

[90turbo]

my bet is the voltage regulator