no voltage to a/c clutch

[thor1701]

ok i have scoured this website in relation to what im dealing with and have tried many things mentioned in the post's, so here is where im at
i have a 96 EB, 4.0 v6, im damn good shape, i had to replace the ac compressor last year due to the bearings in the clutch going to hell and it got extremely loud to drive, once i got everything going, i went ahead and replaced both the high and low pressure switches, i finally got things going, well summer ended and i disconnected the plug going to the clutch that way it wouldnt cycle on while i had the heater on, well its starting to get warm here so i re connected it to make sure everything was happy, it did not turn on, checked to make sure no fuses were blown, checked the pressure, still was there, i even did the bypass switch trick where you put a wire on the low pressure switch to manually turn the compressor on, nothing, then i went to check the voltage at the plug to the compressor, nothing what so ever, wiggled wires around nothing, so came here and did some research, and did some testing, hooked the battery directly up to the plug, while the engine was off, and the magnet clicked on no problem, it spins fine, i just done know which is the pos and neg poles on the plug so i could put power to it while the truck is running, dont wanna screw up and blow a fuse, looked into the relay's and someone mentioned swapping the fuel and WOT relays, did that, no change, all fuses are fine, it worked last summer, dont know why its not getting any voltage this time, and all i have to test is a good handy multimeeter, that and a ob2 scanner that plugs into my laptop, dont know if that could tell if something was wrong or not
any help i will take

 

[thor1701]

just a small update, i hooked both pos and neg up to the plug on the compressor from the batt while it was running, turned on, left it that way for a few, got in the truck and was feeling much cooler air, still zero voltage from the plug itself, tho every so often when i press the max ac button, the rpms go up for a few, but come back down to normal, so no idea what that means

 

[Torqueranger]

Did you check the freon lvls because if it senses it's low then the system will not work...

 

[thor1701]

yes as i said i did, i also used the jumper method to trick the system to thinking its full, in case the switch went bad

 

[budwich]

did you check the fuse AND wiring arriving and leaving the fuse WITH a meter?

 

[thor1701]

i have no idea how to check that, or pull apart the fuse panel to get to the wires behind it

 

[budwich]

well they easiest way is the pull the fuse, check for voltage on one contact of the fuse slot and then the other... that tells you if voltage is arriving ... note your key has to be on. Then measure the resistance of the fuse to see if it is actually good. Finally, put the fuse back in and check that voltage is at the pressure switch...

 

[thor1701]

ok sounds good, want to explain that in a little more detail? as to where i put my probes? i do know how to check a fuse, just not quite sure where to put my probes for the socket as the pos and ground to see if voltage goes through, same with the pressure switch
i will try this tomorrow when its daylight

 

[koda2000]

the fuse has two small holes in its back. put your probes there to check for voltage across the fuse. i'm not clear on a few of your checks... i know you say that you're sure it's not a refrigerant pressure problem and that you've jumped the hi and lo pressure switches, but you also said that you ran power straight to the clutch and the compressure ran but that the interior only became somewhat cool. that sounds like a low refrigerant level problem. how are you measuring the pressure?

if it helps, look here for an electrical diagram of the A/C system:

http://search.ebscohost.com/ Use RRCC and rebsco when signing in

 

[thor1701]

i do have a little pressure gauge that came with a can of r134a i got ages ago and i keep that handy, but what i meant by getting cold in the cabin, it gets back to its normal coldness when sitting idle, i didn't drive around with it that way, i just wanted to see how it worked
also i was told to check the voltage across the pressure switch, not sure how to do that, just stick my probes into the holes on the plug? and im assuming i need to have the truck on and the max ac button pushed and running?

 

[thor1701]

finally figured how to test the voltage on the fuse, pain in the butt to find a good ground....14 volts on the ac fuse in the fuse panel, while car was on, while ac button was pushed as well
i could not quite figure out how to test the voltage going into the low pressure switch

 

[budwich]

The technique is exactly the same... find a good ground and touch the other probe on the "test point" of interest.

 

[thor1701]

ok i did that,, i figured a good ground would be the casing of the alternator, and then put my pos probe in both holes of the switch, zero nothing

 

[budwich]

???? not on the switch... remove the connector from the switch and make sure you are able to contact the points inside the connector. IF your ground is good... there is always the battery negative or wiring from there. Anyways, if you indeed were able to touch the proper points and the measurement is "good", you have found your problem... you have no voltage leaving from the fuse and going to the pressure switch... maybe... although perhaps the technique is a bit suspicious...

 

[thor1701]

yes i disconnected the switch, i first stuck the probes in the hole, nothing, then i pulled out a paper clip and shoved it in to make sure there was a connection, then grounded to the alt and nothing on either side

 

[thor1701]

ok i know my system is really effed up, i decided to go out and play with testing things from the fuse on up, well, i eventually got voltage from the low pressure switch connector, at first it read 14, with the engine running, then it couldnt make up its mind if it was zero or 9 volts, so i connected the paper clip to the other side so both are connected, then took a reading, it went between 6 and 4 volts, kept changing, so i left it that way and decided to check the high pressure switch connector, for a while it was 0 volts, then it started bouncing around between 9 and 5, so i put a paper clip in that one and connected it together, then i hooked up the probes to the clutch connector, and omg there was voltage! but, not very much, i think the highest i saw it go for a moment was 11, then stayed around 6, so i plugged it into the compressor, nothing, so pulled it out and rechecked it,voltage still couldnt make up its mind, eventually went to zero and stayed there so im at a total loss as to wtf it could be

 

[budwich]

ok back to the fuse... as was mentioned here, the top of the fuse has "contact points" (I don't know my self)... did you measure for voltage on BOTH of those points when you said you had 14v there????

 

[thor1701]

yes i did, it took me a while not notice the points on the top, i knew they were there on the big fuses...i found that out the hard way a long while back, but yes 14 on both

 

[budwich]

ok.... now of course there is always more questions... which fuse number are you looking at? basically, it would appear to be a broken wire between the fuse panel output and the low pressure switch... :-( you could try running a wire from the battery to one side of the connector and see if that causes the compressor to run (with your truck running)... one side of the connector will do nothing while the other should cause the compressor to work.

 

[thor1701]

fuse 18
i would agree to a broken wire, only if it was still 0 volts everywhere, but there is some voltage someplace, im going to take a flashlight and see if i can follow wires and see where they lead and make sure they all look ok, sometimes i do hate that plastic crap they are wrapped up in, and do you mean run a wire from the pos batt to the low pressure switch connector? need to find a wire long enough lol its on the other side of the of the truck, but it is an interesting idea
could always use the jumper cables hehehe
i wish i knew more about relay's and what i could jump to see if that did anything, i did follow a suggestion in another post to swap the fuel and the wot relay's and see if that did anything, but no change in anything
wish i could hook up my pc ob2 scanner up to it and find out whats up