Heh all.
I'm spending a little time getting caught up on some overdue jobs on my D2.
One problem I'm trying to track down is that my AC fan has never come on at 212 as mentioned in the rave. Actually it's never come on ever that I can remember.
So far I've verified that the fan runs (jumped the relay).
I did swap in the relay from a donor truck but given that I couldn't verify that it works, I haven't yet ruled out the relay as bad.
What are my other areas to check and in what order? Does the ecu get the temp that it uses to run the AC fan from a different sender than the one that reports via obd2?

If I can jump the fan to work , then it seems my order of "suspects" are relay, temp sender, ecu ?

 

Uses same sensor so if it comes on with AC it should come on when coolant temps get to 212. Only way to check would be to intentionally run up coolant temps. If your temps don't get that high on regular basis you could remove your fan/clutch and idle while monitoring temps for an ops check.
......

 

I should clarify that I haven't been able to get the fan to come on under any circumstance other than when I jump the relay.

 

If you pull the relay, do you have 12 volts on two pins? In most cases, the control and load connections will have constant power. The computer usually supplies the ground to turn the relay on. If you only have power on the load side, look for a blown fuse or bad connections.
If you do have power on two pins, connect a test light to battery positive, turn the A/C on and make sure the ground side control pin becomes a ground and lights the test light. (engine will probably need to be running for this test. The other ones should be fine with key on, engine off).

 

Have you looked at wiring diagram? It just shows the two sensor wires to ECU and one from relay back to ECU to provide gnd to control relay.

AC fan will not come on unless ambient temp over 82.
......

 

Cheers for the replies. I do have 12v at both poles which is how I'm able to jump the relay to manually run the fan.

As has been observed, the challenge is creating the run conditions under which the fan should come on.


I can see temperatures during hill climbing in the 210-220 range, during which the fan doesn't come on. It should come on at 212 according to rave.

If I pull over, temps drop too fast for me to be able to get the hood open to see what is happening. We do get ambient days over 82 degrees but not many in Seattle and they don't always correspond with my days off.

My truck is up there in weight, with oversize tires and a less aerodynamic footprint due to the sd rack and rooftop tent. Consequently the engine really has to work on hill climbs. Hood louvers have helped get rid of the created heat and a HD fan clutch plus tropical genuine thermostat and new rad have my cooling system working well in all other scenarios.

Everything helps however and it really bugs me that the electric fan doesn't activate correctly.

I do still have to add an oil cooler which will help and I also have all the pieces for the inline thermostat mod ready for once I've figured out why the fan doesn't activate.

If I can't get it fixed I may look into adding aftermarket fans with a controller that I can set to come on at the temperature of my choice.

 

Just to clarify what I was saying, you must have two separate pins with 12 volts on them. You'll need a multi-meter or a test light to check. Most relays have four pins, two for control and two for load. So when you test them 2 will have 12v two will have 0v.
I hope that makes sense.
Also, have you checked the relay itself? All fuses?

 

Yes, I have 12v on the two pins that run front to back. The two pins "east/west" have 0v . I haven't checked the relay itself, took the step of pulling the relay from my other d2 where the fan works.
All fuses are good.

 

Pwr you see should be on 30 & 85. Fan runs when you jump to 87.

Relay control circuit needs gnd at 86. Normally GO wire gives gnd through AC panel and/or GW wire through ECM when temp reached 212. Check for gnd at 86 with AC on, if gnd good relay may be bad. If no gnd there check fuse box connector C0573-11 for gnd with AC on. Looks like there is a splice in box that could cause problems.
......

 

Thanks for the diagram!
Superb! I'll dig out the multimeter and check after breakfast.