no cooling fan 2000
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Model: Cherokee
no cooling fan 2000
my 2000 XJ's cooling fans do not kick on. I have tried swapping fan relay out with a known good one, and I have jumped the fan to be certain it was good. I checked for signal at both terminals that supply the electric fan and it never seems to get current even when hot with AC on high. After testing the "B" terminal on the relay what next? What all does this circuit need to "go live"??
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 101
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
To do a quick test of the Rad Fan circuit remove the connector from the Engine Coolant Temperature sensor (ECT), start the engine, see if the fan runs. If it does, the fan power circuit is intact, including the PCM program to turn the fan on in an over temp situation. This will trigger a check engine graphic and a P0118 DTC, which will require clearing using a code reader/scanner, or by disconnecting the battery NEG post connector for 5 minutes.
If the fan won't turn on when doing this, there's a power interruption in the fan circuit.
Check the Rad Fan fuse in the PDC (see pic)
.
Check fuse F10 in the JB (see pic)
If all the fuses are good the fan driver from the PCM may be defective. The driver provides a ground to the fan relay control coil when over temp occurs or AC is requested.
If the fan won't turn on when doing this, there's a power interruption in the fan circuit.
Check the Rad Fan fuse in the PDC (see pic)
.
Check fuse F10 in the JB (see pic)
If all the fuses are good the fan driver from the PCM may be defective. The driver provides a ground to the fan relay control coil when over temp occurs or AC is requested.
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Model: Cherokee
I will check the maxi fuse as soon as wife gets home, as well as ECT test. ECT is the one on the gooseneck, not by the firewall, correct? And what is meant by "the fan driver from the PCM may be defective"? The whole ECU would then need replaced?
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Joined: Feb 2014
Posts: 2,379
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From: Florida
Year: 2000
Model: Cherokee(XJ)
Engine: Golen 4.6L
The fan in the 2000 doesn't work that way. Up to '99, the fan came on with the AC. In 2000 they changed it so that it does NOT automatically come on when you turn on the AC. It only comes on under two conditions:
1. When the coolant temp reaches 221° F. It then stays on until the coolant drops to 217° F. Then it goes off and stays off until the coolant gets back up to 221° F.
OR
2. When the AC high side pressure reaches a certain pressure (which I never can remember). Just turning on the AC will NOT turn on the fan. There's a pressure switch in the high pressure line that triggers the fan when the pressure rises to that predetermined level.
A lot of people who are familiar with the way the '99 and earlier behaved freak out when the 2000 or 2001 doesn't behave the same way and assume their fan isn't working. Take a deep breath and another look and see if it's really not working exactly as designed.
1. When the coolant temp reaches 221° F. It then stays on until the coolant drops to 217° F. Then it goes off and stays off until the coolant gets back up to 221° F.
OR
2. When the AC high side pressure reaches a certain pressure (which I never can remember). Just turning on the AC will NOT turn on the fan. There's a pressure switch in the high pressure line that triggers the fan when the pressure rises to that predetermined level.
A lot of people who are familiar with the way the '99 and earlier behaved freak out when the 2000 or 2001 doesn't behave the same way and assume their fan isn't working. Take a deep breath and another look and see if it's really not working exactly as designed.
CF Veteran
Joined: Mar 2010
Posts: 47,923
Likes: 38
From: Broward County Fl.
Year: 1989 xj sport 2dr
Model: Cherokee
Engine: 12 hole bosch Injectors
The fan in the 2000 doesn't work that way. Up to '99, the fan came on with the AC. In 2000 they changed it so that it does NOT automatically come on when you turn on the AC. It only comes on under two conditions:
1. When the coolant temp reaches 221° F. It then stays on until the coolant drops to 217° F. Then it goes off and stays off until the coolant gets back up to 221° F.
OR
2. When the AC high side pressure reaches a certain pressure (which I never can remember). Just turning on the AC will NOT turn on the fan. There's a pressure switch in the high pressure line that triggers the fan when the pressure rises to that predetermined level.
A lot of people who are familiar with the way the '99 and earlier behaved freak out when the 2000 or 2001 doesn't behave the same way and assume their fan isn't working. Take a deep breath and another look and see if it's really not working exactly as designed.
1. When the coolant temp reaches 221° F. It then stays on until the coolant drops to 217° F. Then it goes off and stays off until the coolant gets back up to 221° F.
OR
2. When the AC high side pressure reaches a certain pressure (which I never can remember). Just turning on the AC will NOT turn on the fan. There's a pressure switch in the high pressure line that triggers the fan when the pressure rises to that predetermined level.
A lot of people who are familiar with the way the '99 and earlier behaved freak out when the 2000 or 2001 doesn't behave the same way and assume their fan isn't working. Take a deep breath and another look and see if it's really not working exactly as designed.
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 101
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
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