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Discussion Starter #1
Hey all
I have a 05 tj 4.0 and the a/c hasn’t worked since I picked it up. Found a couple broken wires and repaired them also am able to spin the clutch by hand. I’m looking for information on what kind of signal could I expect to find when using a power probe at the high and low switch and compressor plug. Also is there a way to manually activate the compressor to see if it is in fact ok. Also checked the fuses and swapped relays for a known good one without change. It seems to idle up a bit when the panel is turned to a/c, so I would think it should be sending a signal to the compressor?

As always Thanks in advance!
 

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You can jump the low pressure switch and that should activate the compressor charged or not, as long as everything is connected properly.
 

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As for manually operating the clutch the best way to start is to pull the a/c relay. Find terminal 30 & see if you have 12v power (from fuse 21 in the PDC). Then make a short jumper wire & jump from 30 to terminal 87. That should give you 12v power to the compressor at the dark blue/black wire & the black wire should be grounded. When plugged in the compressor should engage.

If jumping the relay gets the compressor to engage you can see if it blows cold (of not).

If it idles up when switching the a/c on the pressure switches should be OK & the PCM is getting the proper grounding signal from them. If you want to test them here is how.

With the key on & a/c selected the light blue/orange wire at the high pressure switch should be grounded (unplugged from the switch). There should be continuity between the 2 terminals of the switch. If good, plug the connector in & go to the low pressure switch & unplug the connector. The light blue/white should be grounded & continuity between those 2 terminals on the switch. If good, plug that connector in. Go to the PCM & find the dark blue/yellow wire at pin 10 of the C-1 (black) connector. It should be grounded (you can unplug it to make it easier to check).

If jumping the relay works but the compressor will not engage with the relay in place you will have to check the relay terminals 85 & 86. One of them should get 12v power (from fuse 11 in the fuse block behind the glove box) with the key on & the other should be grounded with key on & a/c selected. Normally 85 would be ground & 86 be 12v but sometimes they are reversed so check both ways if needed.
 

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Discussion Starter #9
As for manually operating the clutch the best way to start is to pull the a/c relay. Find terminal 30 & see if you have 12v power (from fuse 21 in the PDC). Then make a short jumper wire & jump from 30 to terminal 87. That should give you 12v power to the compressor at the dark blue/black wire & the black wire should be grounded. When plugged in the compressor should engage.

If jumping the relay gets the compressor to engage you can see if it blows cold (of not).

If it idles up when switching the a/c on the pressure switches should be OK & the PCM is getting the proper grounding signal from them. If you want to test them here is how.

With the key on & a/c selected the light blue/orange wire at the high pressure switch should be grounded (unplugged from the switch). There should be continuity between the 2 terminals of the switch. If good, plug the connector in & go to the low pressure switch & unplug the connector. The light blue/white should be grounded & continuity between those 2 terminals on the switch. If good, plug that connector in. Go to the PCM & find the dark blue/yellow wire at pin 10 of the C-1 (black) connector. It should be grounded (you can unplug it to make it easier to check).

If jumping the relay works but the compressor will not engage with the relay in place you will have to check the relay terminals 85 & 86. One of them should get 12v power (from fuse 11 in the fuse block behind the glove box) with the key on & the other should be grounded with key on & a/c selected. Normally 85 would be ground & 86 be 12v but sometimes they are reversed so check both ways if needed.
Thanks I’ll give it a shot this weekend
 

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Discussion Starter #10
As for manually operating the clutch the best way to start is to pull the a/c relay. Find terminal 30 & see if you have 12v power (from fuse 21 in the PDC). Then make a short jumper wire & jump from 30 to terminal 87. That should give you 12v power to the compressor at the dark blue/black wire & the black wire should be grounded. When plugged in the compressor should engage.

If jumping the relay gets the compressor to engage you can see if it blows cold (of not).

If it idles up when switching the a/c on the pressure switches should be OK & the PCM is getting the proper grounding signal from them. If you want to test them here is how.

With the key on & a/c selected the light blue/orange wire at the high pressure switch should be grounded (unplugged from the switch). There should be continuity between the 2 terminals of the switch. If good, plug the connector in & go to the low pressure switch & unplug the connector. The light blue/white should be grounded & continuity between those 2 terminals on the switch. If good, plug that connector in. Go to the PCM & find the dark blue/yellow wire at pin 10 of the C-1 (black) connector. It should be grounded (you can unplug it to make it easier to check).

If jumping the relay works but the compressor will not engage with the relay in place you will have to check the relay terminals 85 & 86. One of them should get 12v power (from fuse 11 in the fuse block behind the glove box) with the key on & the other should be grounded with key on & a/c selected. Normally 85 would be ground & 86 be 12v but sometimes they are reversed so check both ways if needed.
All test ok except the ground or the relay isn’t grounded. If I use a power probe and supply a ground it engages the clutch.
 

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OK, the relay gets its ground from the PCM when the other signals (high & low switches are closed which you have checked) are met. So you need to check that at the PCM.

Go to the C-3 (clear or natural color) PCM connector & at pin 11 the light blue/orange wire should be grounded. It is from the low pressure switch. If good, check at pin 24, also a light blue/orange wire to see if it is grounded. That is the PCM output to the relay. You will have to have the connector plugged in & back probe the wire to check this. The pin 24 wire is the one going to the relay & when grounded energizes the relay. If pin 24 is grounded at the PCM but not at the relay you have a break in that wire between the PCM & PDC. The probable places for a damaged wire is under the PDC & in the harness where it passes near the battery where sometimes acid leaks from the battery & damages the harness. Start checking under the PDC following the wire from the relay & note the condition right at the terminal crimp & follow from there.
 

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Discussion Starter #12
OK, the relay gets its ground from the PCM when the other signals (high & low switches are closed which you have checked) are met. So you need to check that at the PCM.

Go to the C-3 (clear or natural color) PCM connector & at pin 11 the light blue/orange wire should be grounded. It is from the low pressure switch. If good, check at pin 24, also a light blue/orange wire to see if it is grounded. That is the PCM output to the relay. You will have to have the connector plugged in & back probe the wire to check this. The pin 24 wire is the one going to the relay & when grounded energizes the relay. If pin 24 is grounded at the PCM but not at the relay you have a break in that wire between the PCM & PDC. The probable places for a damaged wire is under the PDC & in the harness where it passes near the battery where sometimes acid leaks from the battery & damages the harness. Start checking under the PDC following the wire from the relay & note the condition right at the terminal crimp & follow from there.
Sent you a message
 

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Discussion Starter #13
OK, the relay gets its ground from the PCM when the other signals (high & low switches are closed which you have checked) are met. So you need to check that at the PCM.

Go to the C-3 (clear or natural color) PCM connector & at pin 11 the light blue/orange wire should be grounded. It is from the low pressure switch. If good, check at pin 24, also a light blue/orange wire to see if it is grounded. That is the PCM output to the relay. You will have to have the connector plugged in & back probe the wire to check this. The pin 24 wire is the one going to the relay & when grounded energizes the relay. If pin 24 is grounded at the PCM but not at the relay you have a break in that wire between the PCM & PDC. The probable places for a damaged wire is under the PDC & in the harness where it passes near the battery where sometimes acid leaks from the battery & damages the harness. Start checking under the PDC following the wire from the relay & note the condition right at the terminal crimp & follow from there.
Many Thanks for all of the help! This guys ROCKS!!!
 
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