Just bought a new alternator to replace my other new alternator that died very prematurely due to excessive heat. Figured it was just undersized at 100 amps as I have about 120 - 130 amp draw with all electrical accessories, lights, fans, etc running. Replaced it with another new 150 amp Powermaster single wire amplifier and it too is overheating badly within minutes of starting the car. Battery is less than a year old Yellow Top, voltage is right where it needs to be..

Thinking the alternator is overheating because it is charging continuously for some reason , but with an internal regulator is that possible? I have the original 2 wire harness plugged into the alternator, a 6ga wire off the positive alternator post running directly to a distribution block and back to the battery, and a good ground wire from the main harness to the Alternator ground post. Pretty standard stuff. Car is a 1980, all other wiring is stock.

Does something else control the charge cycling of the alternator in these cars other than the Alternator regulator? When I unplug the factory 2 wire plug from the alternator, it continues to register on the Gauge as full voltage and the alternator is still charging, is that right? Could there be something wrong with the electronics in the storage bay behind the seats that is causing this??

At a loss here, any help is greatly appreciated!

 

Contact the manufacturer of the alternator you purchased and talk to their tech dept...that is what they are there for.

As for your alternator...you alternator is always charging when it is spinning or at least it should...and if my memory serves me correctly...the SINGLE WIRE alternators have an 'exciter' that requires you to rev the engine a little bit to activate it and get it to start to charge...or at least that is how I remember it numerous years ago when I installed these single wire alternators.

What is your alternator charging when you have it running??? And I do not mean by the gauge...but by checking it at the battery.

DUB

 

If you have a 120 amp draw at idle,your 6ga wire may be too small. You may want to try a 2 ga or 1/0 AWG for the charge wire AND the ground wire.

 

How the heck are you getting 120-130A of draw?

How hot is it?

If the new alternator is the same case design as your original then it's a ****-poor design. You need to be using an alternator that started life as a CS144 or AD244.

No alternator produces its rated current when the engine is idling. It's a numbers game. You can get the current at a higher rpm but you can only get 50% to 75% of that current at idle rpm. If you really have a 120-130A load then you need at least a 200A alternator. A GOOD one too. Use a 3-wire with the voltage sensing connected to you main distribution block.

 

I do agree that increasing the wire size would be a benefit.

From the graph posted by 'Crimson Thunder'...11 feet of 6 gauge wire is good for 100 amps.

And I also wonder if you are actually using the amount of amps with everything running like you posted....and I am sure that if your have some massive amp for a stereo..that can do it...

I have used alternators for some special builds that came out of an ambulance and they were stout.

DUB

 

120 amps..no way. And, alternators do run HOT. Use an IR thermometer and see, contact the manufacturer of the alternator.

 

Thanks DUB, I'll call Powermaster when they open back up tomorrow and see what kind of help they can be. I seem to avoid calling for support because I've had so many bad experiences, not with them specifically, but in general. Right or wrong, I rely on this forum first and it usually get's me through. Thanks everyone! I believe the battery read 12.7 volts with the car off and 14.7 volts with the car running / charging.

You're absolutely right, at max draw 6ga is undersized, but I believe that will be the exception not the norm and I'll be ok. When I talk with Powermaster I will ask if that could be a reason for overheating. As far as the ground goes, I only have the factory harness ground to the alternator which is probably a 12ga wire, pretty small. However, shouldn't the alternator be well grounded by default as it's mounted to the engine block via an aluminum mount, steel bolts, etc? Would adding a 6ga wire to the frame be any better than that?

My typical amp draw would not be as high as 120 - 130, but it could get that high. With my headlights, stereo, electric fans, HEI, etc. The attached image is from Powermasters directions on how to choose the right alternator. I chose the 150 amp to give me enough juice at idle when I have high draw. When I say it gets hot, I mean hot enough that a drop of water bounces off the case instantly, it doesn't evaporate, it boils.

I've not temp gunned it but I have one and will do that. No alternator is going to last with that kind of heat and will become less and less efficient as the temperature rises, causing even more issues.

Thanks for all the input guys, I'll make a call to PowerMaster and see what they say. Anyone have any idea if there are factors that control the charging other than the internal regulator of the alternator? In looking at the wiring diagram for my car there are wires tracing back to the 'electronics' behind the passenger seat, but I'm not sure what they do. Could there be something there that's faulty and causing a continuous charge signal to be sent to the alternator via the original 2 wire GM alternator connector?

Thanks for all the help!

 

FYI, good winding insulation can withstand 165*C all day long.

IF the alternator is producing around 14V then it's working correctly. The regulator can't force current to flow without increasing the voltage.

 

To answer your question about the electrical stuff behind the passenger seat. If my memory serves me correctly. On your 1980...all that will be back there is a black square box that is your theft deterrent control module...and if you have intermittent wipers...that control module is also there.

AS for you unplugging the TWO wire connector on your alternator and your VOLT meter stays put....I wonder if your GEN light is working in your gauge cluster.

I am ASSUMING that when you engine is NOT running the alternator is not so blistering hot as you described.

ALSO...if you increase the gauge size of the red wire that runs throguh your frame from the junction block in the battery box and goes to the alternator....MAKE SURE that the pigtail wire coming off your POSITIVE BATTERY CABLE going to the junction block is also increased.

NOW...I prefer NEVER cutting the nice red molded cable end to do a modification IF AT ALL POSSIBLE....so ...in this case..I would go to a stereo shop and get one of those gold plated terminal bolts that allow you to attach a wire to it WITHOUT hacking up the factory cable end. And YES...I have cut the end off the cable and bought one of the replacement side mount battery cable ends and use the red covers for it in some special custom applications....SO ..I have done it...but if I do not have to...I don't. I get those from American Autowire....just in case you need it.

DUB

 

Wow, 165*C is 329*F, that's really hot. Maybe the winding insulation can handle it but can the regulators electronics, capacitors, etc?

DUB, as my old alternator was starting to fail (it only had about 1500 miles on it) the GEN light was working as it should to indicate that it was not charging properly.

The alternator is not hot when the engine is off, so nothing weird there. The 2 wire GM plug has 12.8 volts when the car is off and when ignition is turned on to ACC, it drops to 1/4 volt. Is that normal? I did not start the car to see what it reads at that point, should it read 12+ volts?

Just no clue what's going on here but I don't want to fry another alternator in short order. The new higher output unit is getting even hotter than the old one, and doing it faster.

Can a bad / undersized ground wire cause an alternator to overheat? As I said before, it's mounted to the heads / block with an aluminum bracket and I cannot imagine that it's not well grounded.

I'll contact Powermaster tomorrow to get their take on all of this.

Thanks guys.

 

I'm just pointing out how hot parts can get without damage and that many people don't understand the design limits of the different parts. The rectifier diodes can handle easily 100*C. Bearing about 90*C. The regulator is mounted in a little case that is behind the rotor in the cooling air flow to try and try and keep it cooler than the case mounted components. Still, it's likely using high temperature components capable of operating in the 100*C range too.

Your 2-wire plug should have a red and brown wire. The red wire should have voltage all the time. The brown wire should have a voltage that is switched with the ignition switch.

The new alternator being a "1-wire" design means it shouldn't need the red wire and can optionally work with the brown wire. But, it shouldn't hurt anything to hook up the red wire anyways.

What is the output voltage at idle when it's getting so hot?

 

See if you can find someone with a clamp on DC ammeter, that way you can determine the true load on the alternator.

 

Have you tried using a heat gun and measuring the alternator and then the components and surfaces around the alternator.

Could be everything is hot under the hood. Mine gets really hot and every part in the engine bay is scorching after a drive in 80degs temperature.

 

where did you get that chart of amperage draw from?

I don't see how you could be running that many amps, but even so, the alternator would only put out it's rated capacity. if you ran everything at full power at exactly the same time with all the electric motors drawing start-up load at the same time (which is pretty much impossible), it would just drain the battery faster than the alternator could replenish it. like a house with a 200 amp service, you have a service factor % figured in, you never run 200 amps at home at the same time or the main would trip, which is something you could certainly wire in your car to verify (or just use an ammeter to verify your load).

the only way it would get hot is if you were shorting it out without it running, or the bearings are bad/dry and creating heat, or the alternator being connected to aluminum bracket on aluminum head already running hot is acting as a heat sink, which may be a distinct possibility....

as stated before, if you have a one-wire setup, the two prong plug should have a rubber block-off inside blocking those two terminals. it is installed inside of the alternator to keep from hooking anything to them.

have you determined why the old alternator went bad? did the winding get hot enough to melt the varnish coating? bearings seize? regulator or diodes burn out due to heat?

and forgot to add, the CS series have better designed fans on them and is a better base to build a high amp alternator from if you are not already using one...

 

The ONE WIRE alternators I have installed have also had a rubber plug so the two wire connector could NOT be installed....and the ONE WIRE alternator had to be revved up to get it to charge due to an 'exciter' inside the alternator.

I believe your alternator is grounded OK but I would like to hear what you found out when you talked with the company....AND this is ASSUMING that your FRAME to ENGINE BLOCK ground wire is intact and GOOD. It is located on the passenger side of the engine where it attaches to the engine block frame perch for the motor mount and then goes over to where the support bracket for the starter is bolted to the side of the engine block
I am wondering that due to this alternator is putting out much more than the facotry set-up....that the red wire is under sized and needs to be changed to a larger gauge.

AND...is the red wire on the back of your alternator getting really hot when you follow it back towards the firewall area????

DUB

 

Something to think about here. Buddy installed new radiator and dual electric fans. Removed mechanical fan obviously. Alternator got so hot you could not touch it due to low airflow around it. Electric fans point down. Reinstalled flex fan, electric fans still in place, and the alternator stayed cool. Well cool by comparison anyway. I don't think the flex fan did any good for engine cooling but it moved the air under the hood around. Point is, see if you can get some air flow. I have seen alternators with a shroud and air ducted to it.

 

Yep- BMW's use duct work on the alternator and even have a watercooled one...




water cooled housing-





If you are not running any accessories- the alternator should not get that hot-PERIOD. If you have nothing "big" running it won't matter what size wire -OK within reason - say 10GU.

As far as a bad ground- you should still check the resistance from the chassis to the alternator case...if you are not having any problems starting- you very well could have a good motor ground to chassis- but maybe a bad ground off the case of the alternator to the engine.

If the continuity to ground checks out-I'm thinking the alt is just bad- I'd get one that is not a single wire...

 

Output voltage at the alternator is 15.2v at idle and 14.8v at the battery. I talked to Powermaster about the original 2 prong GM plug, and they said it should not be a factor in heat generation and can be run with or without that plugged in.

Working on that but have not found one with enough capacity.

I tried to heat gun it last night, but the case finish is 'natural' and my temp gun does not read properly on it. I was getting readings of ~110*F but it was scorching hot, no way you could touch it for more than a second without pain. I may need a better heat gun as it seems to work on most other finishes. Everything is hot under the hood, but I just wrapped my headers so theoretically it should be cooler than before, yet the alternator is getting just as hot.

I got the Amp draw chart right off of Powermaster's site. I don't think the amp draw is the issue here however. I've got plenty of overhead with a 150amp unit and output voltage at idle at the alternator and battery are very good, alternator is 15.2v at idle and 14.8v at the battery. I am assuming the old alternator went bad due to prolonged heat exposure, but Powermaster did say I could send it in and they can usually determine the root cause of failure by applying their version of 'forensics' to it. I did compare the mounting bracket temp to the case temp last night to test the heat-sink theory, but the bracket was quite cool compared to the alternator or even heads. I think I can eliminate that as a root cause or contributing factor.

Powermaster said running the 2 wire GM plug along with the one-wire hookup to the battery is a non-issue. As advised by someone here already, they said that I should add an additional ground to the Alternator case in the same gauge as the power wire, so last night I ran a 6GA wire from the case to the frame. That did not seem to have any effect on lowering the temperatures. The alternator is well grounded to the motor by the mount, no paint obstructions, etc., so I cannot imagine that is the issue. My motor to frame ground wire is intact and I have no issues with cranking the motor so I think I am good there. The red wire from the alternator to my distribution block is about 8" and it gets warm, but it's hard to tell if that's motor heat or electrical heat and does not seem abnormal. The wire from the distribution block to the battery does not really get warm at all. See picture of how this is wired. Powermaster said that anything over 200*F at the case is going to cause issues, and I have no doubt that mine is over that based on water drops boiling off of it. The other main reason they cited as overheating is belt slippage. They see alternators coming in with shafts that are blue from the heat of a slipping belt. I have no slippage as the pulley is quite cool compared to the alternator case. If it were slipping it'd be pretty damn hot and I can touch it no problem.

The only 'big' thing I have running are the electric fans and they are intermittent. The alternator gets hot as heck before they even kick in from a cold start. I may have to try another alternator, it would seem very odd that I got two bad ones in a row, but it's possible I suppose. My last one was brand new and only lasted only about 1500 miles.

Thanks for all the input guys, really appreciate it. I'm at a loss at this point, what we've tried so far simply does not seem to be having any effect on lowering the temps. I've not been driving the car because I didn't want to burn up another brand new alternator before I figured this out, but at this point I need to get her out of the garage and on the road. Summer is short here in Wisconsin.. Any additional ideas are welcome however!

 

well then you've got to figure out where it is coming from by elimination.

friction
convection
conduction

if it's not electrically generated, and it sounds like it's not, you're going to have to do some more testing, like disconnect it completely and run the motor straight off the battery, no charging at all, and see if it gets hot.

then do the same thing with no belt on it.

then connect it to another car.

 

I honestly feel that 15.2 volts is a bit high....you are getting really close to 16 Volts which can cause a battery to pop....and that is just my thoughts on that...I may be wrong. I prefer to see 14.4 Volts and not much more than that...but that is on facotry alternators. Normally the volt meter reads about 13.4 v to 13.6v when there is a good battery and all ease is good.

Worth check just in case you have not and that is the NEGATIVE battery cable where it is bolted to the frame under the battery box.

'gungatim's' advice seems solid. I would take the electrical of the alternator out of the equation and see if it gets hot not doing anything but spinning.

Lastly...if you can...I would double up on the 6 gauge wire to your junction block and add another one....because with the chart provided above....I would try a larger gauge wire (more than 6 gauge myself)

And for what it is worth...when I am using my IR gun on a surface that seems to be reflective...I apply a dab of black paint and check it there....or actually use a probe thermometer.

DUB