Hello



1987 firbird 5.0 tpi auto tans stock



I keep burning up alternators. I'm on my fourth one. I tested the alt circuit and also did an amp load check on wires. And all is well there. My battery is good my belt is good also. I have taken back 3 alternators and from two different sources and they all failed the in store test. CH/fan fuse is good and belt is tight. but every time I install and turn the car on its killing the alternator. of this I'm certain


I noticed that I have battery to engine ground as well as battery to chassis ground but I have no engine chassis ground. could this be ruining my alternators? Car has never had an engine to chassis ground as long as I have owned it.


also i think one of my fan motors is bad because it does not come on when i ground the A and B terminals on the aldl. could this be the problem since its in relation to the circuit.


I am not grounding any positive lead while installing the alternator either because I disconnect the battery when installing.


lost on this one

 

i saw a '92 lumina that kept blowing alternators,and the cause ended up being a bad coil(actually one of the 3 coils on the 3.1)that was sparking over from the output to 12v circuit,the alternator not liking the little 30,000+volt spike at all-they would often smoke and arc as they fried...CS130,normally found on an '87-92 is the worse alternator GM has made in the last 40 yrs: 85-86 TPI alternator brackets could be used to mount a CS 144 if you continue to have CS130 problems.

 

All my ignition stuff is new. i dont think thats the prob but i will look into it .

 

another queston is how the alt grounds itself

 

alternator just grounds to the engine through the mounts.sounds like your batt/engine/body grounds are ok,but wouldn't hurt to add an engine/ body ground strap-original one on my '82 was behind RH head to a bolt on the firewall

 

i just dont get how i can blow the alternators with out at least seeing some kind of smoke or malfunction indication

 

that is odd-usually when I had a cs130 fail(on a '91 buick 3.8,replaced about 6 over the last 15 yrs)an output diode would short and alternator would make a weird whirring sound and get very hot in no time though they would still sometimes work at reduced capacity.If no funny noises/smoke/sparks,must just have blown voltage regulator.If you have one of the bad ones lying around,could have an alternator rebuilder look at it and see what went bad in it and repair it.

 

Have you checked the main battery ground on the block for being solid and clean ?
You should also look at the positive log of the starter and alternator wire it connects to the starter lug. Sounds like a corrosion or loose connection.

 

Regarding the fans: Only one comes on with the ALDL bridge.
The secondary fan uses a pressure switch in the passenger cylinder head to come to life, which means you have to get the engine very hot and/or have your A/C running.

 

No corrosion on starter lug but there may be paint on the block where the negative cable is attached.

I also dont have a ground strap mounted in the back of the motor like I should. the car never had one. i hear this could cause problems

I think with the next alt im going to wire the alt. externally from the harness and see what happens. if i do this i will only need to wire the lug cable and the red wire from the thre wire plug to the bat right? I am getting mixed signals on what the other wires in the 3 wire plug actually do but from what i can tell they are not necessary

 

The alternator needs to get power to the sense or excighter wire. This can be hooked to the battery stud of the alternator. This wire is on the plug terminal S.
Then if you run a larger gauge wire to the battery you should be set. You can measure the battery voltage not running the start your engine the voltage will go up.

 

On my 84 I kept burning up alternators and eventually found the resistance in the "L" (lamp) circuit was not within spec.
It was wired through the CH relay coil. The relay was working fine but resistance was not right. Changing the relay fixed the problem. (This was a 12SI though, not CS130 like yours.)
I had another car with an SI that kept eating alternators. Turned out to be intermittent short in the L circuit - it was ok checking with multimeter until you beat on the dash.
With above problem, most of the time I was burning up voltage regulators.
I believe the rectifier bridge is the weak link on the CS130 - you could check your bad one to see if this is your problem. If so your problem may be high current or defective part.
You could also be repeatedly getting sub-standard, weak parts to begin with - which has happened to me also.

 

Iirc the 85-87 was a basterd like the SI and cs had a love child.

 

i noticed the charge light doesnt work so im breaking into that today going t o check the circuit

 

Check the resistance in the brown wire going to the alternator. Turn the ignition on with engine off and pull the alternators weather pack plug. You should have a positive 12 volts and a resistance of at least 50 i believe. To check resistance put one lead of multimeter on the battery or battery lug of alternator and the other on the brown wire in connector. No resistance or no voltage could be the problem.

 

ok so i broke into the instrument cluster. Turns out the car never had a "charge Light" because there is no space for one nor do any of the light cover indicate a charge symbol.

But i did find something interesting. The cluster dimmer (remote dimmer) plug was jumped. There are three wires going to the plug Geen , Green/white, and brown. The green wire was jumped to the brown wire in order to keep the dash lights on i suppose. The remote dimmer is absent obviously. When i did a resistance test from brown wire from the dimmer plug to one of the brown wires that on the alternator i get 15 ohms resistance ! why is this happening

another unusual thing is the the 3 wire plug that connects to the alternator has two brown wires (same color) and one thicker red wire. What do the two brown wires do? i remeber changing the plug out and i could have easily swapped these two wires. Would that cause my alt to fry?

 

You need to make sure the L terminal on the alternator plug is a switched 12 volts with a resistance. You should have a red wire (10 gauge?) Blank spot and the L terminal which should be a brown wire. Other wires in the connector should not exist from the factory, simply pull or cut them if you don't want to trace them in the harness.

 

ok im gona check this out tomorrow

 

So i rewired the alt and it worked for a while and it began to overcharge 18v then took a crap. i cant help but wonder why there is a third wire in the pigtail and if this is why it began to overcharge

 

How exactly did you rewire it? Did you check for the correct key on voltage and resistance? if everything checked out and you had it wired as we said it will work or the alternator is bad. Do you have enough belt tension?

 

so how would i apply he proper resistance to the L wire on the plug?

 

First, verify for us that you have it wired correctly and you have a key on +12 volts at the brown wire.

 

yes everything is wired properly i know one of the wires is supposed to have resistance. i rewired the alt outside of the wiring harness so i need to apply resistance to the L wire i think. just not sure how to go about doing that

 

Just go to radio shack and buy a resistor and solder it in line if it is new wiring.