1987 XJ6 Air Conditioning
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Junior Member
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From: Bartlesville, OK
1987 XJ6 Air Conditioning
My A/C intermittently switches from Cold to Hot without any operator inputs, with the Temp setting still on Full Cold. Vacuum lines are secure with no leaks, coolant is full. Has anyone had experience with this anomaly?
Thank you
Thank you
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Joined: Jan 2009
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From: Akron, Ohio USA
Welcome to the forum Rolljk.
I'm glad you found us. It is good that you posted in the New Members section. Now, you should probably explore into the section for your car and be ready to learn a ton!
I'm glad you found us. It is good that you posted in the New Members section. Now, you should probably explore into the section for your car and be ready to learn a ton!
Last edited by JOsworth; Sep 17, 2011 at 06:06 AM.
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Joined: Mar 2008
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From: Pacific Northwest USA
As guesses go the most-likely-by-far culprit is the amplifier. It's a $250-$300 guess, though.
The Jaguar service manual has a thorough (and thoroughly confusing) troubleshooting guide for the climate control. There are multiple tests and checks that you can perform....some of them only making sense if a "known good" amplifier is in place.
Anyhow.....
When the system self-changes the temperature do you hear the slight humming of the servo motor? You'll need to manually select Lo fan speed to hear it and, even then, listen carefully.
If you DO hear the servo motor it suggests that the servo "thinks" hot air is being requested and is dutifully obeying the request. If so this suggests a sensor or amplifier problem.
If the temp change occurs with no hummm from the servo motor it suggests that a problem is occurring independant of command central, so to speak.
In that case I (or in any case, really) I'd check the vacuum hose to the heater valve. The valve is designed so that vacuum holds it closed and lack of vacuum opens it. Your valve is obviously opening so make sure the vacuum hose is in good shape.
Hope this helps a little
Cheers
DD
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Junior Member
Joined: Sep 2011
Posts: 4
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From: Bartlesville, OK
1987 XJ6 Air Conditioning
Doug,
I'll try listening for the humming of the servo motor again; so far we haven't noticed that.
Thanks much!
Kevin
=====================================
1987 XJ6 Air Conditioning
My A/C intermittently switches from Cold to Hot without any operator inputs, with the Temp setting still on Full Cold. Vacuum lines are secure with no leaks, coolant is full. Has anyone had experience with this anomaly?
Thank you
I'll try listening for the humming of the servo motor again; so far we haven't noticed that.
Thanks much!
Kevin
=====================================
1987 XJ6 Air Conditioning
My A/C intermittently switches from Cold to Hot without any operator inputs, with the Temp setting still on Full Cold. Vacuum lines are secure with no leaks, coolant is full. Has anyone had experience with this anomaly?
Thank you
As guesses go the most-likely-by-far culprit is the amplifier. It's a $250-$300 guess, though.
The Jaguar service manual has a thorough (and thoroughly confusing) troubleshooting guide for the climate control. There are multiple tests and checks that you can perform....some of them only making sense if a "known good" amplifier is in place.
Anyhow.....
When the system self-changes the temperature do you hear the slight humming of the servo motor? You'll need to manually select Lo fan speed to hear it and, even then, listen carefully.
If you DO hear the servo motor it suggests that the servo "thinks" hot air is being requested and is dutifully obeying the request. If so this suggests a sensor or amplifier problem.
If the temp change occurs with no hummm from the servo motor it suggests that a problem is occurring independant of command central, so to speak.
In that case I (or in any case, really) I'd check the vacuum hose to the heater valve. The valve is designed so that vacuum holds it closed and lack of vacuum opens it. Your valve is obviously opening so make sure the vacuum hose is in good shape.
Hope this helps a little
Cheers
DD
The Jaguar service manual has a thorough (and thoroughly confusing) troubleshooting guide for the climate control. There are multiple tests and checks that you can perform....some of them only making sense if a "known good" amplifier is in place.
Anyhow.....
When the system self-changes the temperature do you hear the slight humming of the servo motor? You'll need to manually select Lo fan speed to hear it and, even then, listen carefully.
If you DO hear the servo motor it suggests that the servo "thinks" hot air is being requested and is dutifully obeying the request. If so this suggests a sensor or amplifier problem.
If the temp change occurs with no hummm from the servo motor it suggests that a problem is occurring independant of command central, so to speak.
In that case I (or in any case, really) I'd check the vacuum hose to the heater valve. The valve is designed so that vacuum holds it closed and lack of vacuum opens it. Your valve is obviously opening so make sure the vacuum hose is in good shape.
Hope this helps a little
Cheers
DD
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