Zags

Hey guys,

I've been having alternator trouble in my 97 c5 for a few months now. It began with the original alternator testing bad. I replaced it with a remanufactured unit from O'Reily's only to have that unit start overcharging. At this point I took the car to a shop that I trust for diagnosis. They tested all the major circuits, cleaned up some corrosion. A week later they confirmed that the issue was with the O'Reily's alternator. That unit was replaced under warranty. This one behaves a little better, but still throws codes. Every time after sitting, after being on the road for an hour, etc.

In any case, I've decided I'm done with O'Reily's / AutoZone, anything of that nature. Hopefully I can get my money back on the junk I bought from O'Reily's but I'm not holding my breath. The dealership however want's $700+ for the part alone (no labor), and I can't bring myself to spend that on an alternator. Where are you guys buying alternators from? NAPA? Rock Auto? Thanks!

Bill Curlee

The problem most likely stems from you installing the INCORRECT GM Alternator. Even though they look exactly the same, yours (or should I say C5 alternators) has internal circuits that are monitored by the PCM. If the PCM doesnt detect that circuit, you get the charging system fault messages.

You need to find the correct Valeo (french made) alternator. The one pictured has an overrun clutch and would be for an automatic transmission C5.

http://www.dbelectrical.com/p-11554-...FcEWHwodoQALdA

Regular non overrun pulley:


http://www.partsgeek.com/gbproducts/...FUSPHwodpGABdA

Bill Curlee

THIS,,,,,,,,,,,,, Is the schematic for your charging system. It is unique to 97 although not that much different than 98-2004 C5 Charging systems



The small plastic connector on the case of the alternator is the connector with the wires that interface with the PCM.

Bigdad

If you have a valeo alternator look in front of the plug for the wires. The part number for the regulator should be there. If you have regulator part number M526 that is the wrong one for an early c5. I had mine rebuilt with that regulator and I was having the same problem as you. I found out the right regulator number is M530.
https://www.aspwholesale.com/index.p...roduct_id=9304

About 3weeks ago I paid $39.55 shipped now they want $54.13 plus shipping.
Bigdad

dadaroo

Bill is correct.

I worked with a guy about 2 months ago that went thru 3 O'Reilly's alternators and I determined it was the alternator. Incorrect for the C5

He went to AutoZone and the first one worked perfectly. He did get his money back from O'Reilly's.

Here is the Thread.

https://www.corvetteforum.com/forums...tem-fault.html


Mr. Sam

Zags

That sounds exactly like what's happening with my car. Thanks for the info. I'll let you guys know how it turns out.

dadaroo

The correct C5 alternator should have 3 pins on it . This is to match up to the schematic above, those are on the upper right side. The Red on the left is the BIG one that provides the charging current and voltage. The connector on your harness has a 4 cavity connector of which only 3 are used.

I bet if you look at the alternator you got it will only have 2.

Keep us informed


Mr. Sam

Zags

Replaced the alternator with a unit from AutoZone at lunch. Autozone alternator has 4 pins molded in the cavity.

Issue persists though. Charge System Failure on startup. Have to rev to 1500-2000 before the voltage come up. Even then it reads around 12.8v.

lionelhutz

Did you keep the original? If yes, get the regulator BigDad posted and try that. I believe it comes with brushes and everything which should get it working again. Typically an an alternator fails due to brushes, regulator dying or the bearings failing and becoming noisy. You could run a little emery cloth on the slip rings to shine them up for the new brushes if you so desired.

Zags

Turned it in for core charge 4 months ago.

lionelhutz

Hmm, is the replacement physically the same? If it is, you could change the regulator on it. Sucks to do on a new part, but it could fix the problem.

I've been thinking that possibly a resistor from ignition switched power to the L terminal could be a band-aid type fix to these alternator problems to make these replacement alternators work. But it could also blow-up the BCM. I'd have to do some testing on my car but it's in storage. The stupid weather turned rather nice as soon as I put it away.....

dadaroo

Pull your dash DIC codes. Unfortunately 97 and 98 may not throw the ones I am looking for, P1537 and P1638.

Are you reading 12.8 AT the battery? That is what I care about right now.


Mr. Sam

Bigdad

in your picture under your thumb nail is there some numbers. That could tell if you have the right regulator. Transpo is the manufacturer.

Bigdad

Zags

I'm not sure where this starts to make a difference, but 3 years ago, my PCM died and was replaced with 99-02 PCM. Had it professionally done and I've had no problems with it. Again, not sure if that makes a difference.

Before I blip the throttle, I'm reading 12.0 at the battery, and 12.0 at the alternator. AFTER I blip the throttle, I get 14.6 at the battery, and 15.0 at the alternator.

I have codes 1637 H and 1638 H C.


These are the only numbers on either of the two alternators I have right now.

AutoZone
http://s17.postimg.org/wiybdq9lb/Full_Size_Render.jpg

O'Reilly
http://s17.postimg.org/ubu2pt4b3/IMG_5611.jpg
http://s17.postimg.org/3s1hno3rj/IMG_5612.jpg


Let me know what y'all want me to do. Thanks!

Bigdad

I was hoping there was a number on the plastic right in front if the plug connector. To search the internet to see if it has the right parts in the regulator.

M530
Voltage Regulator / Brush Holder Assembly.
12 Volt, B-Circuit, S-FR-L Terminals, 14.5 Volt set point
For :
Valeo 110A Alternators
Used On: 1997-2002 Chevrolet Corvette 5.7L (350) V8 , Fiat LCV - Europe (1999-2002)
Replaces: Valeo 593342, 9RC7109, 2541935B, 2546366C, 2546493C, 2542521B, 9RC7109 Unit Nos: GM 10246634, MAGNETON 9-517-186, VALEO A14VI21, VALEONEW 439217, VALEOTECH 2541926
Lester Number : 13721
Features : Transpo w/ 10K Ohm Resistor w/ External Sense 10 Sec LRC and Soft Start Active Lamp Choke Function No Overvoltage Indication and Loss of Sense Light Which Compliant to OE OE Compliant Soft Start Stator, Ignition, Light Activation, Stator, Ignition, Light Activation


M526
Voltage Regulator / Brush Holder Assy.
12 Volt, B-Circuit, S-FR-L-D Terminals, 14.8 Volt set point
For: Valeo Alternators
Used On: (2003-97) Chevrolet Corvette
Unit Nos: GM 10246634; Valeo, 2541916, 2542445A, A14VI21, A14VI39
Lester Nos: 13721, 13864
WAI Ref. Nos: 1-2079-11VA Note: 4-pin connector, but only S-FR-L used. Active lamp function - with output. With FR Resistor. With External Sense.

Both of these regulators are for a c5 but the M530 is for oe.
Bigdad

Zags

Just blank plastic on both. No sticker, nothing stamped.

Bigdad

looks like it is up to Mr. Sam, Bill Curlee, and the others much smarter than me, to solve this problem.
If I was in your shoes. I would give the alt. back and get my money back. I would call Marc at Vettenuts. He might have a good valeo 110 you need. If it needs a rebuilt get it done locally.
Bigdad

dadaroo

I don't know how long that P1637 has been there. Do this, turn the ignition ON but do not start the engine and see what voltage is at the L terminal (small Red wire). You can unplug the connector if you need to.

Boy Zags, you're making this tough for us.


Mr. Sam

lionelhutz

I'd also be curious what the voltage is with it connected, running and charging.

CactusCat

You know how us Okies are..