Heater blower : no fan when I ask hot air
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xj40_197042 (01-18-2022)
#23
[SOLVED] Heater blower : no fan when I ask hot air
It works
So, thanks to @NTL1991 I checked the diagram.
When the engine coolant is above 40°C, 5V is applied to AC4-13. I never had this 5V ! So I joined AC4-13 with AC3-6 to force 5V.
And I have the fans spinning, whatever temperature I ask
Thanks a lot @NTL1991 if found the solution because of you
(but don't misundestand me, I'm still interested with your Electrical binder )
The shunt to test :
Now, I have to make the shunt nicer, and put all the stuff back on.
So, thanks to @NTL1991 I checked the diagram.
When the engine coolant is above 40°C, 5V is applied to AC4-13. I never had this 5V ! So I joined AC4-13 with AC3-6 to force 5V.
And I have the fans spinning, whatever temperature I ask
Thanks a lot @NTL1991 if found the solution because of you
(but don't misundestand me, I'm still interested with your Electrical binder )
The shunt to test :
Now, I have to make the shunt nicer, and put all the stuff back on.
#24
That’s great news!
I’m curious if you happen to see a part number on the Climate ECU.
Do you know if it’s ever been replaced?
The 1990MY and 1991MY Diagrams show the 5V signal through the inhibit switch. The 1991/1992MY diagram shows the ground signal through the inhibit switch.
I’m curious if you happen to see a part number on the Climate ECU.
Do you know if it’s ever been replaced?
The 1990MY and 1991MY Diagrams show the 5V signal through the inhibit switch. The 1991/1992MY diagram shows the ground signal through the inhibit switch.
Last edited by NTL1991; 01-18-2022 at 09:13 AM.
#25
#26
No, I can't see part number on Climate ECU.
I don't think it has been replaced.
I "found" All Data, and the diagram you gave me is the same in 1990, 1991, 1992, so it is the good one : when the coolant is above 40°C, the ECU wants AC4-13.
Once again, thanks @NTL1991
I don't think it has been replaced.
I "found" All Data, and the diagram you gave me is the same in 1990, 1991, 1992, so it is the good one : when the coolant is above 40°C, the ECU wants AC4-13.
Once again, thanks @NTL1991
I’m just not sure why you have a mismatch
Last edited by NTL1991; 01-18-2022 at 09:24 AM.
#28
Just wondering if all these tests are performed on a hot engine?
On my car, the blowers will not start on warm/hot setting either if the engine hasn't reached operating temperature. The delay varies of course, but usually it takes about 2km of driving before they start. The blowers do work on cold or a/c setting immediately with no delay. This is how the system is designed, correct?
Larry
On my car, the blowers will not start on warm/hot setting either if the engine hasn't reached operating temperature. The delay varies of course, but usually it takes about 2km of driving before they start. The blowers do work on cold or a/c setting immediately with no delay. This is how the system is designed, correct?
Larry
#29
@NTL1991 can you take a picture of the 1991/92 diagram please ?
@Lawrence Yes exactly, the system is designed to not send cold air when the engine is cold and the driver asked for hot air. But in my car this does not work.
By the way, as @NTL1991 stated, it seems I have a mismatch : I don't have either the good A/C ECU either the inhibit switch.
@Lawrence Yes exactly, the system is designed to not send cold air when the engine is cold and the driver asked for hot air. But in my car this does not work.
By the way, as @NTL1991 stated, it seems I have a mismatch : I don't have either the good A/C ECU either the inhibit switch.
#30
Just wondering if all these tests are performed on a hot engine?
On my car, the blowers will not start on warm/hot setting either if the engine hasn't reached operating temperature. The delay varies of course, but usually it takes about 2km of driving before they start. The blowers do work on cold or a/c setting immediately with no delay. This is how the system is designed, correct?
Larry
On my car, the blowers will not start on warm/hot setting either if the engine hasn't reached operating temperature. The delay varies of course, but usually it takes about 2km of driving before they start. The blowers do work on cold or a/c setting immediately with no delay. This is how the system is designed, correct?
Larry
The ECU calculates the heat/cooling load based on the sensors and will look for the inhibit switch signal before allowing fan operation if there is a heating load. That signal is ignored by software when there is a cooling load.
#31
Okay, reviewing your pictures I can say with some confidence that your Climate ECU was replaced with an older (likely used) unit.
I can tell this from the fact that your inhibit switch is normally open, that your ECU is commanding fans on with 5V at AC3-6 instead of a ground signal doing it. And the fact that your inhibit switch wires are green and black, the green wire being grounded as it should according to the later diagram.
How long have you had the car? How long has this been an issue?
You could swap in a correct late 1990-1991/1992 ECU as per the TSB I posted early on, which shows the correct matching ECU and inhibit switch part numbers. Jumping out will work fine (you will lose the inhibit feature) but to be perfectly correct you can swap the newer ECU in.
I can tell this from the fact that your inhibit switch is normally open, that your ECU is commanding fans on with 5V at AC3-6 instead of a ground signal doing it. And the fact that your inhibit switch wires are green and black, the green wire being grounded as it should according to the later diagram.
How long have you had the car? How long has this been an issue?
You could swap in a correct late 1990-1991/1992 ECU as per the TSB I posted early on, which shows the correct matching ECU and inhibit switch part numbers. Jumping out will work fine (you will lose the inhibit feature) but to be perfectly correct you can swap the newer ECU in.
Last edited by NTL1991; 01-18-2022 at 11:49 AM.
The following 2 users liked this post by NTL1991:
Don B (07-15-2022),
xj40_197042 (01-18-2022)
#34
#35
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Welcome to the Jaguar Forums! It's great to have you with us, and congratulations on acquiring a Jaguar XJ40.
There is a lot of good information about the blower motors at this link:
Jaguar XJ40 Air Con Blowers
Please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.
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Cheers,
Don
#36
Can anyone help me?
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