I did some searching and couldnt find whats happening to my car with in someone elses problems so here we go. It does have a new alt just put a 140 amp on it, has a 6 month old battery, both tested at above 14v when on. I can turn every other electrical componet on and the voltage will not drop much at all. But when i turn on the AC the voltage will drop slowy to 8-9 volts and even if i turn the AC off it will not come back up. I pulled the clutch sensor plug off and turned on the AC and the same thing happend so i plugged it back in and restarted the car ( which brings the voltage back to 14) then i unplugged the plug on the back of the compressor and turned on the AC inside. That obviously worked cause the compressor was not getting any voltage. Now the diagram i read said theres a diode in paralle with the clutch sensor. Now im thinking that something is wrong with this diode because i will complete the ground even if the clutch sensor is unplugged.

Does anyone know what the diode is there for? And where the heck the diode is located? Any other suggestions or ideas? Im going to keep searching to see if i cant find a pic of where the diode is. Thanks for the help

 

Just a WAG, but it could be some combination of reduced idle speed, the fans running, a faulty alt. not re-energizing. What does the car idle at?

 

As far as the diode goes, Im not quite sure what its for. Maybe its for transient voltage suppression. Anyway, it shouldnt allow current to flow with the A/C compressor cluch connector disconneted. Incedentally, IIRC, thats where its located. I suspect that if it was the cause, youd be making a bee line for the fire extinguisher. From the sound of it, theres a considerable load on the battery thats draining it.

 

dimented got what the diode is for. the inductive voltage spike when the A/C clutch turns off is more than enough to kill the ECM, i have been told the A/C clutch can spike over 25,000 volts, the clutch coil & any other coil including the relays work just like the ignition coil, turn the voltage off to them & you get a voltage
spike through the system. like dimented said, the diode is right there at the A/C compressor clutch connector.

the compressor shouldn't use alot of current,.. IIRC seems like about 6~10 amps or so to engage it & around 4~5 amps to hold it in.

as far as your low voltage, also check at the battery when your seeing low voltage inside the car, you may have a bad connection somewhere.

 

Ill go out and check the battery right now. The car idols normal at about 750 rpm, the thing with the rpm is even when i rev the car up the voltage does not gain. Thanks for the clue on the diode i was going to try and bypass it, which would not have been a good idea lol. Anyone have any starting point on where i should look? Other people i have talked to said it sounds like i have a bad ground somewhere. Im trying to find out where that could be. I would of figured it would be somehting on the AC circuit that is grounding itself out when the compressor is turned on. But the only wires i see are to those 2 plugs on the compressor and the one on the condensor. The condensor switch is new about 1 year old or so IIRC. Let me know ill be back to tell you what the battery voltage is when i turn the AC on

 

Ok back. I tested the voltage at the battery with the AC on and it tested at 13 volts. I tested the alt with the AC on and it also was at 13 volts. I tested the connector on the clutch sensor and it was reading 11.7 volts. The guage in the car is reading right about there if not a little lower ( damn analog guage ). So i guess is this right? Is the guage i have bad since the battery is reading 13 volts. I dont have any clue where the guage gets it reading from. Im starting to think its the guage but please clue me in on where it gets its reading from. And let me know if i need to probe anywhere else for helping this.

Problem im having is why when i turn the AC back off the voltage does not come back up to 13-14??

 

13 volts is OK at idle. I wouldnt sweat it. If it drops below that, then you know you have a problem.

 

Where does the guage get is reading from? Is it directly off the battery?

 

It probably gets its reading from a nearby ground and a +12 volt feed off the ignition. The wiring diagrams would tell you for sure. The gauges in these cars are the most inaccurate gauges ever made. Dont trust them.

 

Ok something is definatly screwy lol. I just went out for a drive to test my theory that it was just the guage being messed up. I got about a mile and the guage went into the red 8. The car seemed to drive fine no rough idle or anything and AC still blowing cold, but i tried to use my windows to see if they worked fine and the were going up and down slow as if there was actually 8 volts or so going to them. When i got home i left it running and check the voltages again. The battery was reading around 11 volts and so was the alt. The wires leading from the alt to inside the car were reading right around what the alt was readin. The guage inside however never got off of 8 volts. So i killed the AC let it sit for a min and killed it. I tried to start it and it sounded like it was a almost dead battery. Then the guage went up to normal around 13 volts and now it starts fine. WTF lol, any ideas?

 

Its probably a crap alternator. Some of those remans cant last a week. I have a pep-boys No-Start&#174 reman. alternator and I replace it at least every four months under the guarantee. Its already starting to act up again. Sometimes it fails to energize. Id take teh alternator and have it load tested to see if its just a problem of a failing alternator with inadiquate output to run all the accesories and the coolant fan(s).

 

Well the alt i have on now is brand new from summit, 140 amp. The one i had on there for 3 months was a reman 105 stocker.

 

Anymore ideas that i can check, otherwise i think i might bring it to a shop and see what they have to say.

 

Well i was playing around with the wiring more today and i have found that if i disconnect the high pressure switch from the AC compressor that the voltage will go back up to 13-14. So if i turn the AC on the voltage drops. I can then turn the AC back off and the voltage will not change, but if i disconnect this switch the voltage will come back up. I tried this with the clutch switch and it was good. Is there anything in the path to this switch i can check to see if its bad ?

 

I went and check some continuity between some wires. The white wire from the prssure cycling switch goes to the high pressure switch on the back of the compressor in LT Blue, that checked ok. From the green on that switch to the clutch switch also green it checked out ok.