I moved this post from electronics because i'm looking for a little more impute.

The first symptom is that the fans both come on as soon as i turn the key before starting it? And as soon as i start it, the volts stay at 18 and the fans are still running, which is not healthy?

So last fall before storage i got the alternator tested, tested good. So then i drove it to car shop, still reading 18 volts. Parked the car, walked in for about a minute or two and a technician went outside and starded it up, then drove it into one of the bays. He got out, opened the hood and tested the alternator at the battery and it was just fine, reading 14 volts. So we both looked at the guage inside the car and it was also reading 14 volts. So all he could tell me was that it was just fine and if the volts went up again it probly was the alternator. So after standing there for a minute waiting for it to rise in voltage, nothing happend. So i got in my car and drove it away. For the first five miles it looked like it fixed itself. But as i kept driving the volts started creeping up and finally resting at 18 volts. What would make the volts fluctuate like this?

The problem im having is, when the guage was reading 14 volts all the horse power and torque were present. But as soon as the guage reads 18 volts, it just overpowers the system, resulting in major hp loss. Maybe that symptom will help diagnose the problem?

I've been through the car and nothing is out of place, that i can see.

Im looking for some serious help with this one so don't hold back. If anyone can lend a hand it would be greatly appreciated.

------------------
1989 Chevrolet Camaro Iroc-Z28
5.0 Liter H.O. TPI 5-Speed G92 Performance Package

Mods:
K&N Air Filters
Flowmaster-American Thunder Dual Cat

 

do you have an amp or anything extra that would put extra load on the charging system? rear defroster stuck on? my guess is you're alternator isn't big enough for your needs and it's full fielding on you. it shouldn't read over 16.

------------------
ICON Motorsports

1st & 3rd
MM Black Diamond Lodge 538 F&AM

 

That or the voltage regulator is bad. They do weird things like that when they are dying.

 

Yeah, actualy I just told someone in another thread, I am not sure where the reg is, but if it is easily accessable, go get one of those "cans of air" hold it upside down, and spray it on the reg. The stuff that comes out when held upside down is at -60 degrees F and is bound to cool off any malfunctioning piece of electronics. If you start to see condensation though, back off, water will hurt more than heat I used this to test dying CPU's when I worked for a computer shop. If freezing the processor cured the "Windows Protection Error" you got a bad chip. Same w/ the reg.
Good luck


------------------
Corry Lazarowitz
clazarow@voicenet.com
clazarowitz@hotmail.com
SLP 1 3/4" headers, 3" cat back (stock cat )MSD ignition. MSD Blaster SS coil. More soon when funds are avail...

 

Everything is original except for those mods, no amp, or anything needing extra juice. The defroger has a light that goes on when you press it so thats not on.

I guess i will start with replacing sensers and then maybe even the alternater, even though it tested ok out of the car.

------------------
1989 Chevrolet Camaro Iroc-Z28
5.0 Liter H.O. TPI 5-Speed
G92 Performance Package

 

I've had that problem, it is the voltage regulator. It is located inside the alternator. It is not worth replacing just the voltage regulator, or trying to rebuild the alternator, just get a reman one from your local parts store. Doesn't cost much more and they are usually done better than the average shadetree can do. As for the fans and other sensors and switches, it is possible that the high voltage has damaged one or two of them. When you fix the voltage problem, then figure out if anything was damaged and replace what needs to be.

------------------
89 Transam GTA, 350TPI, auto, 3.27 rear, dual cats, gray.
Magnaflow cat-back,
K&N open element,
Best E.T. 14.63@95mph

 

89,

Can you verify the dash mounted voltmeter with a separate meter? If the voltmeter is correct, the high voltage (over 17VDC) is not doing the ECM any favors.

Inspect the rear case half of the alternator closely. There is a "D" shaped test hole in the rear cover. Just inside the test hole is the test tab for the regulator bypass. If some object is causing this test tab to ground intermittently, the alternator will go to full field current and maximum voltage output.

The same could happen to the system if the regulator was failing internally. In either case, the alternator would need some attention.

Excessive voltage will cause the ECM to be unable to regulate a 5VDC supply to the critical engine sensors and logic in the ECM. It could also possibly overclock the processor, toast the MOV in the ECM power supply circuit, and cause erroneous sensor readings and unusual operation of the ECM. The ECM may have already been damaged if the cooling fans are starting as soon as the ignition is turned on. This should only occur if the AC pressure sensor is above 375PSIG or the coolant temperature is above 223°F, or if the ALDL diagnostic terminal is grounded. My guess is that the ECM thinks that the diagnostic terminal is being pulled low because the battery and system voltage are very high. This may be a permanent condition for the ECM after it has gone overvoltage, or may disappear once the system voltage is normal.

Good luck.

------------------
Later,
Vader
------------------
"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

Thanks Guys!