No power to AC compressor?? Need further assistance

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Do you have power at the AC fuse in the fuse box? As I recall, I went through the about the same steps and couldn't get power to the AC fuse. At that point I bypassed the thermistor (which you did) and I also rechecked the previously bypassed pressure switch and found that the pressure switch bypass was not done right (loose). One or the other got the power to the AC fuse and then all worked.
 
I do have power to the fuse on both sides. So far I have bypassed pressure switch, heater sensor on block, and thermistor. But not all at the same time. I have had the pressure switch bypassed the whole time only (have checked jumper to ensure good connection with test light) The AC switch on the heat/ac unit triggers a clicking/relay sound out of the AC amplifier. Power directly to compressor from battery and blows cold. At this point is the only thing left the AC amplifier?? It will be hot in no time..Thanks for the help. I feel I am getting close.
SUMMIT CRUISERS said:
Do you have power at the AC fuse in the fuse box? As I recall, I went through the about the same steps and couldn't get power to the AC fuse. At that point I bypassed the thermistor (which you did) and I also rechecked the previously bypassed pressure switch and found that the pressure switch bypass was not done right (loose). One or the other got the power to the AC fuse and then all worked.
Click to expand...
 
Last edited:
Anymore suggestions. Latest update in last post. Thanks:confused:
 
still no ac... I have been checking for a bit now with schematic from FSM. First I get no power from nuetral saftery switch to ac amplifier. I put power direct to ac amplifier at the black wire (power source from NSS) And still no ac! If I put power direct to white/ blue tracer and ac kicks right on. This eliminates that part of the circuit (engine cut relay, temp switch, ac clutch) AC switch on and I have power to blue/ yellow tracer. I dont know. I am thinking that the ac amplifier is bad. I have direct 12v power into the thing and nothing out for the compressor circuit. Any input on my finding would be appreciated
 
scrowley said:
still no ac... I have been checking for a bit now with schematic from FSM. First I get no power from nuetral saftery switch to ac amplifier. I put power direct to ac amplifier at the black wire (power source from NSS) And still no ac! If I put power direct to white/ blue tracer and ac kicks right on. This eliminates that part of the circuit (engine cut relay, temp switch, ac clutch) AC switch on and I have power to blue/ yellow tracer. I dont know. I am thinking that the ac amplifier is bad. I have direct 12v power into the thing and nothing out for the compressor circuit. Any input on my finding would be appreciated
Click to expand...
I am going through similar problems, and am stumped myself. One thing though, on the black wire to the ac amplifier, from the neutral/park safety switch, that one should only get voltage when the starter is engaged, its what turns the compressor off when your starting the engine. If you check while its cranking, should read 12v then.
 
Thanks for that info. I couldnt tell that from the schematics. Guess I should hook that back up. Do you have any trace of power going into the ac amplifier? I am going to order a used one and hook it up and see what happens. What have you done for troubleshooting so far?
 
On mine, the compressor clutch was engaging, but would barely turn. You could turn it by habd pretty easily. When i started checking voltages, with the compressor wire disconnected, it was gettting 12v to it, but connect it and iy dropped to 8v, im assuming from being under a lot of resistance.i can jump the compressor to the battery and it works fine. I think im dealing with muliple problems now, not sure what i did, but now the clutch doesnt engage at all..checked voltages and i have nothing coming into the ac amplifier at terminal 2, the blue and yellow wire, which comes from the heaater control switch :confused:. If i jump that wire, it does engage the clutch, but again, only at 8 volts! Also, when the compressor is connected, the whole ac system drops to 8v, at least as tested at the amplifier. Oh, i almost forgot, now i have a leak, too. :crybaby:
 
gibby2235 said:
If i jump that wire, it does engage the clutch, but again, only at 8 volts! Also, when the compressor is connected, the whole ac system drops to 8v, at least as tested at the amplifier. :crybaby:
Click to expand...

The voltage drops because when the circuit is energized the current is flowing and there is always a voltate drop across a resistor. You need to think about the circuit as two resistors in series. The first resistor is the wires and amplifier before the clutch magnet (where you are measuring the voltage). The second resistor is the magnet coil. The voltage drop is proportional to the ratio of the two resistors. The typical resistance for the coil may be a few ohms (maybe 2-10), while the wire should be very low (a fraction of an ohm, like 0.01). You are seeing a voltage drop of nearly 50%, so the wire resistance must be close to that of the magnet coil.

Read the Wikipedia entry on "resistors" for more inight into DC circuits.
 
Pinhead, thanks again, i do get it about something acting like a resistor, im just stumped as to where that something is. Now im not getting power to the ac amp from the heater switch (was before when i first tested it). Dont know if i shorted something out or what. Fuse is good. Dontt think thats where the original problem orinates though, because if i bypass that and jump it from somewhere else i still get the voltage drop.
i had been hoping to avoid pulling the whole dash out, not that its that difficult, but guess im going to have to get to the switch anyway.

Scrowley, at the ac amp, what are your voltage readings at each wire?
 
i have 12v with ac switch on at blue w/ yellow tracer. and the 3 red w/green tracer is 1.37v with ac switch on. no power at white w/ blue tracer to compressor. no power at any other at any time.
 
scrowley said:
and the 3 red w/green tracer is 1.37v with ac switch on. QUOTE]
Hmm, I have nothing at these. I thought that these were ground as long as everything was working correctly... I've done a bunch of searches and cant find an answer...I'd say that right there might be the answer to one of our problems! We need to know exactly what voltage (or lack of) those are supposed to be.
Click to expand...
 
Did you try charging WITH THE ENGINE OFF, through the high side in a liquid state.DO NOT open the low side. Are you sure you have a vacuum? MIke
 
I thought red green was ground also as per schematic. I tried grounding these wires with no diff. results. :confused: Its about to start getting hot out....we are running out of time.....lol. Have you tried a new amplifier? I think I might buy a used one from ebay. In my case when I put 12v to the compressor circuit right after the amplifier the ac works great. So for me I know this throws out the chance that circuit to the compressor is my prob.
 
Yes I did. When I put power to the compressor circuit the ac works great. nice and cold.
Michael Hanson said:
Did you try charging WITH THE ENGINE OFF, through the high side in a liquid state.DO NOT open the low side. Are you sure you have a vacuum? MIke
Click to expand...
 
Well I tried another AC amplifier......Still doesnt work!!!! Back to the drawing board. I didnt check any reading just plugged it in. Any other suggestions of what and how to check would be greatly appreciated. Thanks
 
Ok so here is my update. I recently took the power from the green /yellow tracer which gets power from ac switch and spliced it direct to the white/blue tracer that feeds the compressor part of the circuit. Has been like this for the last few days and works GREAT! I just dont like fixing things the wrong way and still trying to find the solution the right way. I have gone threw the FSM with the EWD and everything checks out perfect except one strange reading.

As per fsm the check on pg 117 is for the ac ampl. plug. All the reading are perfect with the truck not running but with key on as per fsm. The reading between 8 & 9 which should be continuity is perfect with truck off with key on BUT when I start the truck and take that reading it shows +voltage of about 5v and sometimes 1.37v!!!!!!! It is actually feeding that voltage to the ac thermistor. Even if I unplug this connection it still wont work because I think the ac amplifier wont turn on the circuit due to this reading. Can someone please help.
 
Dude, My bad

Anyways I finally fixed my issue this morning!!! After some time now on and off getting frustrated. It ended up being the wire gong to ac amplifier from dual pressure sensor. No continuity and in turn no voltage to the ac amp. I cant believe I looked past this but it happens. I was just focused on the small voltage to the red wires going to ac amp. After I ran a new power wire from pressure sensor direct to ac amp. In the beginning improper r134 was an issue also. I'm glad this is all over for now. Hopefully the rest of the system is up to far. It sure blows some cold air though. Thanks for the reply's. I can say I know this ac system quite well now....
CJF said:
Dude.

Pick one thread to keep alive; not both.

I just replied to your other thread and now I see this one.
Click to expand...
 
Me too. I'm going to Rausch Creek in Penn. for the Gothan City Landcruiser event next weekend and I sure need a/c for that. 10 yrs ago I could care less about a/c but these days Its a must. Part of getting older I think...lol
CJF said:
:lol:

Glad you got it sorted...
Click to expand...
 
You must log in or register to reply here.

Share this page

Back
Top Bottom