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Thread: P38 A/C Blows Warm.

  1. #1
    Join Date
    Apr 2008
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    MN
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    P38 A/C Blows Warm.

    My A/C blows warm and I occasionally get the little notebook code on the display of my 99 RR. Last week I inspected all fuses and even swapped a few relays to try and get the compressor clutch to engage. No Luck there. Today I verified the the refrigerant level was correct and the clutch still did not engage. I have tested for power at the compressor - 0v. I ohmed the connector to ground and had good continuity. I started visually inspecting the system and did find the sensor on top of the Drier was unplugged. I plugged it in and still no engagement. I unplugged the sensor in the high side line next to the drier and jumped the two terminals together in hopes it would work, Nothing. I am pretty sure my outside air temp sensor is working correctly cause it has always been pretty accurate with the temp. I am also pretty sure the inside temp sensor works as I was able to get the fans to change speeds using the cigar lighter test. I did jump power and ground to the compressor and it will engage and blow cold air. So what is preventing my compressor from engaging when I have the A/C on?

    Any Thoughts?

  2. #2
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    Quote Originally Posted by Rfactor View Post
    My A/C blows warm and I occasionally get the little notebook code on the display of my 99 RR. Last week I inspected all fuses and even swapped a few relays to try and get the compressor clutch to engage. No Luck there. Today I verified the the refrigerant level was correct and the clutch still did not engage. I have tested for power at the compressor - 0v. I ohmed the connector to ground and had good continuity. I started visually inspecting the system and did find the sensor on top of the Drier was unplugged. I plugged it in and still no engagement. I unplugged the sensor in the high side line next to the drier and jumped the two terminals together in hopes it would work, Nothing. I am pretty sure my outside air temp sensor is working correctly cause it has always been pretty accurate with the temp. I am also pretty sure the inside temp sensor works as I was able to get the fans to change speeds using the cigar lighter test. I did jump power and ground to the compressor and it will engage and blow cold air. So what is preventing my compressor from engaging when I have the A/C on?

    Any Thoughts?
    Bad fuse box under the hood. I had the same thing happen to me. Simple fix.

  3. #3
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    Apr 2008
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    What was wrong with the fuse box? Was there a poor connection on the underside or an internal failure? I suppose I could check for power at the connector on the underside of the fuse box. Do you remember which one it is?

  4. #4
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    When you said it blew cold air when jumped, was it cold or just cool? Also how did you verify that the compressor had enough freon when you couldn't engage the compressor?
    I think you may be low on freon, kind of normal, and might want to go back to the old jumper wire, let the a/c run for a bit then check the freon with a set of guages and also the air coming thru the vents, to see how cold it is blowing.
    Mike

  5. #5
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    Actually I have access to an A/C machine and sucked it down ran a vacuum for 15 min, let it sit for 5 min and it held its vacuum. After that, I charged it to spec. And when I say it blows cold, I mean I had a thermometer in there and it was 40 degrees.

    So that pretty much rules out the low charge theory. Can anyone supply me with a wirring diagram of the system?

  6. #6
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    Quote Originally Posted by Rfactor View Post
    Actually I have access to an A/C machine and sucked it down ran a vacuum for 15 min, let it sit for 5 min and it held its vacuum. After that, I charged it to spec. And when I say it blows cold, I mean I had a thermometer in there and it was 40 degrees.

    So that pretty much rules out the low charge theory. Can anyone supply me with a wirring diagram of the system?

    4.0 or 4.6 ?

  7. #7
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    Apr 2008
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    4.6 Hse

  8. #8
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    Quote Originally Posted by Rfactor View Post
    Actually I have access to an A/C machine and sucked it down ran a vacuum for 15 min, let it sit for 5 min and it held its vacuum. After that, I charged it to spec. And when I say it blows cold, I mean I had a thermometer in there and it was 40 degrees.

    So that pretty much rules out the low charge theory. Can anyone supply me with a wirring diagram of the system?
    When you sucked down the system, did it have the correct amount of freon?
    How the front electric fan come on both if the engine is hot or when the A/C has full head pressure. If not that could possibly be the problem, the ECU won't let the A/C run if the fam is bad.
    Good luck,
    Mike

  9. #9
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    Quote Originally Posted by Disco Mike View Post
    When you sucked down the system, did it have the correct amount of freon?
    How the front electric fan come on both if the engine is hot or when the A/C has full head pressure. If not that could possibly be the problem, the ECU won't let the A/C run if the fam is bad.
    Good luck,
    Mike
    To your first question: No, The system was about 1/2 full.

    I don't really understand your second question. If it is related to the cooling fan, all I know is that it seems to always be on with the key. I asked about its operation when I first got the truck cause you literally just turn the key to the run position in the middle of winter and the radiator fan turns on high. I thought this was odd cause you would think the vehicle would warm up faster without the fan running.

    Actually after typing that out I am thinking if the High Pressure switch was faulty it would not only keep the compressor from running, but wouldn't it also keep the cooling fan on high if it was reading to high of pressure?

    Or is the fan always supposed to be on?

  10. #10
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    Sure could be the issue.
    Mike

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