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my car start acting up couple days ago. Usually when AC is on, the idle drop down to 300rpm. The dash light is very dim after I shut down the car while the cooling fan still on. Dash light come back to normal when cooling fan shutdown.
I thought its just the cooling fan draining too much voltage, and thinking about continue driving it until weekend then I can swap out the fan/relay... big mistake.
it start losing power on the freeway. Once it die, I don't have enough juice to start it back up. I got it tow home. I charged up the battery, battery never get pass 11.5v. I still manage to start the car with such weak juice... put a voltmeter on... its only 10.4 or so volt! rav the car actually cause the voltage drop. Turn out I was running on total loss system on the highway trip!
So here is my question... should I just swap out the alternator (as well as the regulator, 944online has the whole thing for sale), or there are more debugging to find out what else might be the problem? my car is reaching 130k.
Can confirm. The alternator on my 944S was failing after taking it to the local auto shop to have it tested. Brought it back home, took it apart, and one of the two brushes was just gone. Pulled a spare alternator off the shelf, but for an NA, and the part number for the brush sub assembly was identical. Installed it, had it re tested. Jumped up to 14.1V output.
You can get just the brushes at Napa and I prefer a good solid OEM voltage regulator to a cheapo new one. Check youtube for vids on how to replace the brushes.
130 K miles is about right for alternator replacement on most cars. Some get more before it craps out but 130 is right in the range. Hope that the brush replacement goes well and that you get a good solid 14+ volts out of it.
There is no solid 14+ volt. It is still a total loss system.
new battery + new voltage regulator... I severance next would be the alternator.
There are two wires connecting to the alternator... a small wire look like a ground and a big positive wire. Will those be any problem? Anything you guys suggest to check before I drop $200 on a rebuild alternator?
Yes there's a few things to check. First check the belt. You should not be able to turn the fan on the alternator. Apply as much force that you can to try to turn the fan.
Second, that small wire (blue) is not a ground, it's the excite wire. This circuit supplies a small amount of current to the alternator's rotor to start the charging. When the ignition is on current flows through the ignition switch, charge light, and rotor Illuminating the charge light. When the alternator is charging it can supply it's own power to the rotor, with power at rotor, current is no longer flowing through the excite circuit and the charge light goes out.
If the alternator starts to slip from a load, it can't supply power to the excite circuit and the charge light comes back on.
The larger wire supplies power to the electrical system. It may have high resistance. This can be checked by doing a voltage drop test.
The alternator ground/mounting can also have high resistance. This can also be checked by doing a voltage drop test also.
YouTube has many videos on how to do a voltage drop test.
And lastly, your RPM's should not drop when the A/C is on.
07-23-2016, 09:15 AM
Need help... electrical
