I'm getting these readings from the pfc commander.
About 2 weeks ago my readings were 14.3 highest on a 4th gear pull to 8k rpms it was 14.0-14.-3

I've driven my car like 10 times the last 4 months. Letting it sit for 2 months one time and 2 other times of 2 weeks each. Each time my battery died totally and I had to charge it.

Today we noticed the charge light on and my voltage was only going to 12.2 max! 11.7 at idle or something. Then I got on the highway to go home and the voltage started dropping a 10th of a point every 10 minutes. After 2 hours it was at 9.8! I turned my headlights off and drove and it would go to 11 again. Then all of the sudden I look down at its at 13.5-13.6 and it stayed like that all the way home and I just drove the car 2 more times tonight already and its the same.

So my friend says the alternator is going slowly. Has anyone else had weird readings like this? And I'm curious to how close I was to the car shutting off when it was in the 9s. Also, we drove the car pretty hard at 11.5 or so volts when we didn't notice it was that low. Could you possibly blow up the engine because of a bad alternator since the fuel pump would only get that voltage??!@!
If I had floored it and hit 17psi with the 9.8 volts it would be over right? Does the pfc do anything to correct for this voltage? I doubt it since it doesn't even retard timing with the knock sensor.

Well thats my long boring story but it made for an exciting trip home because I was pretty sure I wasn't going to make it.

-MY fd sux

 

hey surge,

i went through the SAME EXACT problem. its your alt. if your turn on your car you should hear your air pump clicking (a.p. clutch engaging and disengaging). your voltage kept dropping because you were prob running off of the battery, then all of a sudden your alt came back on.

as far as your motor going because of the loss of power... im not 100% sure. i think if you had no power or low power (like you said 9 volts) your entire car would shut down before your fp went out.

i would be more worried about pulling high psi, getting at high speed, then losing power along with your hydrolics to your brakes. i guess in worse case just pull the e-brake.

i am on my third alt. first one went out the same way you described, i the bought a used alt off a forum member, but that alt went out three weeks later and finally i am getting a brande new alt. i am getting this new alt from silverrotor.

https://www.rx7club.com/showthread.php?t=363914
it will take a couple weekes but you dont have to give up a core, has a one year warranty, and cheaper then if you go to your local auto shop. its also not a rebuilt alt!!!!

best of luck

ian

 

Ian great information

I'm glad that I'm not alone. I did take my alternator apart 2 times to polish it and repolish it but had no issues putting it back together correctly I thought...This was about 6 months ago. It is the original alternator and my car just hit 55k miles. I guess 10 years will do that to an alternator.

Well thanks again and I think I may spring for that alternator from that guy but I'd have to send him my covers cause I do want it to be polished.

Yanni

 

Hydraulic for the brakes run on a vacuum brake booster which has a one way check valve to the intake manifold. During running , if the engine dies off , the brake booster will allow 2-5 vacuum assisted braking before all the vacuum is depleted from the booster . Even with out the vacuum brake booster you still will be able to brake , but the braking force need will be very much greater .