jungy

I have been battling Charge system fault issues like many other C5 owners and have tirelessly tried anything I can find to remedy my issues. My car is a 1999 frc.

With the engine off and the key in the on position I am getting 11.8v at the battery and the alternator but I am only seeing 10.8v on the L field wire on the alternator connector.

At idle I am seeing 14.4v at the battery and the alternator. The DIC shows 13.4v.

So far I have done the following:
-remanufactured 110 amp alternator
-M530 voltage regulator for the valeo 110 amp alternator per: https://www.corvetteforum.com/forums...nator-fix.html
-big 3 4 ga. wiring upgrade with a 100 amp fuse in the charge wire
-repaired my ignition switch per the DIY thread
-inspected and cleaned factory ground connections under hood

I for the life of me cannot figure out why I am still getting a "charge system fault" message and a generator F terminal range high error. I know I'm not going to get the exact same voltage at the battery as the cluster but seeing a 1v difference at the cluster and L wire on the alternator seems suspicious to me. Any guidance would be much appreciated.

GravelSurfer83

Check all of your fuses and the starter cables. Throw a charger on the battery over night then have the entire charging system checked out. A dead cell in the batt is possible and the vette does some crazy stuff with a low batt.

dadaroo

11.8 at the battery is DEAD for the C5 electronics. Fix that first.


Mr. Sam

jungy

I've gone through the fuses and visually inspected the fusible links at the starter, all apear to be good. I havent checked the resistance of the wires but the voltage sense wire that runs from the starter to the alternator connector gives me the same voltage reading as at the battery.

The battery is a 1 year old optima red top. It reads 12.4v with the key off. The 11.8v is with the key on and a load being placed on the battery.

jungy

Another oddity I am finding is that the DIC voltage only is .1-.2v off of the battery voltage with the engine off and the key is in the on position.

dadaroo

The ignition switches are crap and the sanding contact repairs do NOT repair it to OEM specs.


Mr. Sam

jungy

That may be my next attempt at this.


Another thing that I checked was I probed the ecu fuses in the under hood fuse box I am getting the same voltage as at the battery. when I get a chance I'm going to check the l terminal voltage at the ecu.

popshumphrey

Could it be a bad battery? I have had a battery go bad in a year. It does not sound right to have that low of voltage with the key on. You can have that checked at any auto parts house.

jungy

Well I got back to it again and thoroughly cleaned all the terminals at the starter to a bright shiny brass. They didn't look too suspect they just had typical oxidization for the age. Unfortunately, this didn't work.

I also back probed the ignition switch with my multi meter and I an only seeing a .5 volt loss with the battery at 12.6v with the engine not running.

lionelhutz

With the key on and engine off you should get 10V on the L terminal.

You should get a scan tool on the car and check the F terminal duty cycle with the key on and with it running.

If you don't want to do that then you need to verify the wire from the F terminal to the PCM is not broken or shorted to ground or shorted to power.

jungy

I'll check the L terminal voltage as well as scan the duty cycle of the F terminal tonight and report back with my findings.

Pounder

wrong alt. ?????

lionelhutz

I forget, 10V with the alternator disconnected.

jungy

Well I think its time for me to revisit this. I am still having the charge system fault messages and I did end up ordering a new ignition switch as you guys had mentioned.

I tried to log my f-terminal duty cycle with hp tuners since that is the charge system fault error that I am getting but unfortunately it doesn't give me any logged data.

jungy

I've finally fixed my Issues I ended up getting a pretty good deal on a low mileage used French Valeo alternator out of a crashed car and as soon as i fired up the car there was no charge system fault. I've put 65 miles on and have yet to see any charging issues.