hey everyone


i searched for anwsers and really didnt find any so i figured i ask. ok heres what happened


last night me and the girl friend were driving around in the FD and everything was fine!! ran nice and smooth with no problems! i noticed my PFC commander read 10.2 volts and my water temp was 84 degrees usally it reads 13.0V-14.5V and 86-88 degress but i paid it no mind to it. today on the other hand i drove to work and had no problems but on my way home the RPMS dropped to 500-600, and it seemed like it was about to stall out. my rpms are always 750-800 at idle ( i know this cuz i watch my PFC ALL THE TIME ) and my volts jumped from 6.0V-8.2V and out of no where it jumped to 13.5v and back down....( strange i know! )also when i reached home it stalled out on me, it took for ever to start again but after that it would not start, i jumped it from my gf's car and it started right up, disconneted it and it ran for about 5 mins before it stalled out again..

im thinking its the Alternator, its still the stock one, and i replaced my battery about 2 months ago, i dont ever push my car like a nut or anything and i maintain it very well...im just looking for opions and comments to support my theory. please help

thanks

-Tony

 

Most likely the alternator or something else in the charging circuit. I just fixed a similar problem for a customer. If you can wait a week or two I can get to it. I am in the process of moving my shop. I am in North NJ.

 

From the facts you laid out, I would start at the altenator also. You replaced the battery not too long ago and the car cranks everytime (no starter problem), altenator is next. You can get one fairly easily from the for sale section. If you need help replacing it, let me know. I work at Ray Catena Mercedes Benz in Edison, can get the car in one day after work, no problem.

 

thanks for the help guys : ) i'll look into a new alternator, i had mine polished and with a new greddy pulley ( like 250 just for the polish job ) and do u think its worth me rebuilding it or do u think its just shot? also i scheduled for a tune on tues. what are the odds me getting my car back on the road by tomorrow night?

 

Take it to any auto electric shop and have it rebuilt. Most of the time, the brushes are worn and that's about it, should cost in the 50-75 dollar range to have it rebuilt. Most give a 1 year warranty on their rebuilds as well.

If you buy one from a parts store like napa or the like, it;s just a rebuilt that they are raping you on, AND they are going to take your core from you.



Just so you know, a bad alternator can trash a battery FAST. Even though you just bought that battery, you might want to have it checked out after you sort out your alternator.

 

Wow, you got bent on the polishing.....I sell freshly rebuilt and polished alternators for $165 all day long provided there is a useable core......

 

def sounds like the alternator.
Goodlellafd3s, with your polished alt's do I need to send you mine or do you just supply the housing?

 

alright, so i had my alternator rebuilt, i had the guy rebuild it with better internals, 170 amps and 17.5 volts( with a greddy pulley ), 225 amps and 18.5 volts ( with a smaller pulley ) BUT the car is still running the same. it reads 9.5 battery volts on the PFC commander and drops to 8.3 volts, now that i have a better ALT. why is the car running the same? i have the greddy pulley on there now but i will be switching it out later when i buy a smaller belt. any suggestions?

 

Have you thoroughly checked your battery posts and terminals?

macca_33, you would send out you existing alt to be rebuilt and polished.

 

it's the battery. i had one that went out within a week of running it on my car. it doesn't matter if they're brand new... batteries fail. do yourself a favor and take the car to autozone and have them run a charging check on the whole system. it's free and they'll tell you what's wrong with it.

A bad alternator can also wreck a battery.

 

i was thinking it may be a bad ground. but then again the car was fine a week ago and i wasnt messing with the terminals or wiring, but im def guuna go ahead and go to autozone, thats a good idea! i'll let u guys know what happens



BY THE WAY

i was doing research on high amp ALT. for the RX7 and its actually 75% cheaper to have ur original one rebuilt with better internals and also if u link up an other ground to the actual ALT. shell the amps and voltage jump up about 15%. which is nice considering all u have to do is make a 2nd ground for it, reason why i know this is cuz when i went to have my ALT rebuilt the guy who did it for me showed me with a voltage meter hooked up how much of a differance the 2nd ground makes

 

aight, so i just got back from auto zone and i had them check my battery, battery was good, but i still went ahead and bought an optimum red top batt. while i was there i had him recheck my ALT. and it showed it was pushing out 13.4 volts. BUT when i looked at my PFC it showed it was pushing 8.7 volts at idle, im stumped....i changed the ALT. to a high amp output, i changed my battery and i even re-wired my terminals, i even made a better ground for the battery and the car is still doing the same thing as before, its running slightly better with the new battery but i still dont see why my PFC is showing such low voltage, i DO have a system but its been off because im afraid of overloading the alt or battery. what do u guys think? could my PFC be mis-reading? i mean its accurate with everything else.

 

Well, if your alternator is working to specs and you have a new battery and your PFC is reading 8.5, I would then go to the next assumption; that you have an electrical issue somewhere.

The PFC is a computer, it just displays diagnostic data that it is receiving from your engine so there is clearly something else going on.

What I would do is get a voltmeter and try to trace your hot lines - if you can figure out where the PFC gets its readings.

 

just a thought....have you checked your engine ground at all?

 

yea the ground is fine, in fact, re-did the ground yesterday so i know its not that, and as far as the voltmeter, where would i begin? ive never delt with an issue like this one before