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Discussion Starter #1
Hello, this is my first visit to the forum as a member.
My issue is with an 03 CRV. The radiator and condenser fans won't turn on. Fans are newer, replaced last summer.
I've checked the fuses, relays, replaced the fan switch. The fans run when the fan switch is disconnected and the connector is jumped.
The thing is that when jumped the fans come on immediately once the ignition is turned on, even with the ac off? Once connected to the new fan switch (I tried three different ones) the fans won't come on.
I have constant battery voltage at the fan switch connector any time the ignition is on. That doesn't seem right? But still the fans should come on?
Can't find a discernable wiring diagram. Any ideas or opinions appreciated.
thanks
 

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Those circuits are ground switched. Do the fans come on when you turn the A/C on? If they both come on with the A/C, the circuit should be good. If they don't come on after it warms up, you may have a bad switch. For the fan switch to turn them on, it has to get up to 210-212 degrees. So make sure it is getting warm enough to begin with.
 

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This is from the 05-06 service manual. I doubt they changed this circuit with the updates to these two year models.

Rad fan.jpg
 

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Discussion Starter #4
Thanks for your response.
The fans don't come when the ac switch is on. That's the problem I'm trying to remedy.
The fans come on when the fan switch connector is jumped. So I know the fans work, the fuses and relays are good.
I replaced the fan switch (three different switches tried).
I'm trying to get the fans to come on with the ac switch.
 

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Discussion Starter #6
Wonder if the wiring is different for the 03?
The number 14 fuse under dash in the 03 is for the mirrors.
No other under dash fuse related.
Take that fuse out of the diagram the only thing left is the wire going to the ecm.
Anybody have a pin out of the ecm?
thanks
 

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Since it has two separate sources for ground. One or the other should turn them on. You jumped the connector and they ran. So I suspect the circuit is intact. Just so we are clear, you jumped the connector for the temp switch on the bottom of the radiator, right? Not the fan connector?
 

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Discussion Starter #8
Since it has two separate sources for ground. One or the other should turn them on. You jumped the connector and they ran. So I suspect the circuit is intact. Just so we are clear, you jumped the connector for the temp switch on the bottom of the radiator, right? Not the fan connector?
Yes, I jumped the connector for the temp switch on the bottom of the radiator and both fans come on. But they come on whether the ac switch on the dash is on or off. I think they're supposed to come on only when the ac switch is turned on?
 

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Ok, here is how that works. Fan control circuit is ground side switched. Two sources for the ground in that circuit. One is that fan switch. The other is the PCM/ECU. They operate independently of one another. When you turn the A/C on, the PCM supplies the ground to energize the relays. Otherwise the fans won’t come on until the engine heats up to around 210 degrees and closes that fan switch on the radiator. When you jumped the connector, you supplied the ground for the circuit to energize the fan relays. At that point, it doesn’t matter if the A/C is on or off.

That being said. If the fans don’t run with the A/C on, I suspect that either the wire from the PCM is broken, or there is a bad ground for the PCM somewhere. I’ll dig around and see if I can get some more information on the ground circuit for the PCM.
 

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Discussion Starter #10
Ok, here is how that works. Fan control circuit is ground side switched. Two sources for the ground in that circuit. One is that fan switch. The other is the PCM/ECU. They operate independently of one another. When you turn the A/C on, the PCM supplies the ground to energize the relays. Otherwise the fans won’t come on until the engine heats up to around 210 degrees and closes that fan switch on the radiator. When you jumped the connector, you supplied the ground for the circuit to energize the fan relays. At that point, it doesn’t matter if the A/C is on or off.

That being said. If the fans don’t run with the A/C on, I suspect that either the wire from the PCM is broken, or there is a bad ground for the PCM somewhere. I’ll dig around and see if I can get some more information on the ground circuit for the PCM.
I think you're exactly correct. Looking for a pcm / ecm pinout.
thanks again
 

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Check all your ground connections.

Both fans will come on when temperature switch is jumped no matter what if the fans work. By jumping the connection your basically turning the switch on.

Also are we sure the PCM supplies the ground when AC is engaged? It may also be part of the system from the climate controls I will check my manual when I get home (I have the manual that covers 2003, which is what I have)

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