I am have a issure with the voltage readin on the gauage dropping down to about 8 volts when i kick the AC on. I am torn between wether it is my altenator or my compressor causeing the problem. If the bearings in the compressor are going out then it could be causeing drag and therefore causeing more draw on the system, or the alt. could just not beable to hold the voltage. I have recently replaced the battery, so i know that has nothing to do with it. Anybody got any ideas as to which way i should attempt to go 1st. The compressor is about 1 and 1/2 years old and the alt. im not sure of, prob 2 or more years i would think.
Thanks a ton.

Matt
91 Formula Firechicken

 

It could be either of those, or several other potential problems.

the first thing I would do os verify the reading of the dash gauge with a separate voltmeter, directly at teh alternator output stud and again at the battery. You may have a wiring problem instead of a load or alternator issue.

 

Ok ill try that when i get back home. Im pretty sure its a load problem because when the charge is shown to be droped, the windows sure dont like to come back up. Im pretty sure its the alternator, i plan on bringing it to /shutters, Autozone to let them do a charging test on everything. Thanks for the reply

Matt Andrews

 

I just had to replace my alternator for a very similar reason, but it didn't require the AC to be on. Does it ever happen when the AC is off?

If you notice the lights flicker and the voltage jump between 8-9 and then to 12/13 you know you have some issue with the alternator not keeping up. If it happens w/o the AC but with other accessories on, I'd say its the alternator.

If you need one get a lifetime replacement warranty unit from AutoZone, mine has paid off a few times!!

My guess is its the alternator.... I'll bet it can't provide enough current to keep up with the electrical load when you turn on the AC.

With the engine running, try turning on ALL the accessories except the AC including your defroster, stereo, headlights, fans, wipers, etc... If the voltage drops then then you know for sure its the alternator. Check with a voltage meter then it should be like 13 volts+. If its 8-9 something is wrong.

You could also do as your saying, just take it to AZ and have them test it out. I'd be a bit nervous if its intermittant that they might say its good though.

 

iM HAVEING THE EXACT SAME PROBLEM I put on a new high amp alternator and am still haveing bad chargeing problems.

 

REALLY!! Well crap then lol. Does yours drop if you kick the vent fan on high also or only with the AC?

 

Yes it does. I am thinking of running a wire from the alternator directly to the battary + post. So then i will hacve a direct connection to the battary and keep the old connection hooked up as well that goes to the distribution block.

I know for some odd reason the volts drop down near the red at idle. Then i will turen my head lights on and it will jump up a little below 13 volts then i turn them off it will stay then drop down againl. IT has done this with 2 alternators so i know it cant be that. I am literly goping flippin crazy.

Do you think my 2 wire hook up thing will work?

 

Well im am by no means a wiring genius, but i dont see why that wouldnt work. If there is a problem in the existing wire going to the alt. then that would prove it for sure. Im thinking there is some definate wiring problems there with the headlights uping the voltage at idol. The only time my voltage drops below 12-13 V is when i kick the AC on ( drops to about 8 ) or if i kick the fans on high it will drop it a couple volts. Mine is seeming to be more simple than yours is now lol. Hopefully someone can help us both out with some words of the wise

 

My volts also drop when i turn the AC on or just my vent fan. I woul dlike this problem fixed so i can tackle my cooling problem. My car likes to overheat when the AC is on lol.

 

Well with my overheating problem i hard wired my fans(both) to the ignition on wire. I was starting to think that doing that was causeing the voltage drop but it didnt effect anything. Im probably going to fix the wiring to hook it up to a switch, but thats when i get bored.

 

iF YOU GO TO THE COOLING board you will see what i had done to ttry to get my car to stop overheating. It didnt work.

 

Ok with the voltage dropping, It does not drop but a very small amount when i put on all the other loads other than the AC. Once i put the AC on it drops gradually down to about 8 volts. I changed my fan wiring set up to run off a switch ( which works awsome ). But im still have that damn volt drop, i just bothers me that i cant run my AC in arizona w/o worring if something might stop working. I know its not just my dash gauge going nutz because when the volts drop i can barely move my windows up or down. I think im need to just by a alternator to start since its pretty old, and because i have no idea what else it could be. The AC compressor when kicked on sounds normal too. Any other ideas before i go by a alt.

 

Mine is still doing the same thing yours is and i just put on a new 140 amp alternator and at ngiht with lights ac etc on it gets near the red. I have no clue whats up with it.

 

You may want to check what alternator is actually on there. I had one of the remanufacturers give me an alternator that put out way too little current, and it died very shortly and did the same thing you're talking about. You also should check the integrity of your battery cables and other wiring to make sure everything else is fine.

 

I know its chargeing when i drive but at idle it goes very very low Im thinking of running another wire from the alternator to the battary. Do you think that would help?

 

I'd just make sure the stock wiring is in tact before adding any extra wiring. If it's not charging correctly there has to be a problem with the alternator, the wiring, or the guage.

I'd also verify that the guage is accurate how Vader mentioned.

As for your overheating problem, you should check to see that your cooling fan turns on with the AC. Sounds like you may have some wiring problems.

 

I would look hard for a bad ground. I had the same trouble with my truck. Then one day when I was changing the starter I happened on to the bad ground. The problem is long gone now