Jacked-up condesnsor fan operation

JL Rockies · **Posted:** Thu Apr 28, 2011 12:50 pm

Back in February I replaced my fan clutch and t-stat when I did the timing belt and I looked forward to maybe one last season with the KJ without having to drive around the desert with the heat on before I sold her.

Last weekend, I went down to Comb Wash to explore ancient indian ruins and I was so looking forward to seeing my coolant temp gauge sit at 12 oclock while crusing over the many steep grades between SLC and Blanding... but no... just like the old days, I'm cranking the heater on full blast to keep the needle out of the red... THIS IS BS!!! (sung to the tune of "This is Sparta!")

Last night, I had the KJ in the shop and for giggles I turned on the AC to see if the little fan turns... nope.
Hoping that the fan itself is OK, I pull both the hi and low relays and energize the coil on each and both "clicked". I was ready to jump 12V to the outputs to check the fan so I turn on the AC again, plugged one relay back in and the fan kicked on... put the other relay back in and it shut off. The fan will work with 1 relay plugged in to either socket but will not work with both relays plugged in at the same time.

Whassup wit dat?

papaindigo · **Posted:** Thu Apr 28, 2011 1:43 pm

Wish I could read wiring diagrams better but check page 8W-30-18 in the 2006 FSM. Is it possible both relays must be totally good for both circuits to work? Yes I know you said they both clicked but is that enough to confirm that they work?

geordi · **Posted:** Thu Apr 28, 2011 4:27 pm

I have EXACTLY the same operation, only with one relay in place will the fan turn. Interestingly enough, when I plug the second relay in, for just a brief moment, the fan speed increases before it shuts off.

This tells me that the COMPUTER is turning the fan off. I don't know where the computer is getting the temp signal (or even if it is) that would somehow convince it to turn the fan ON... But I have given up on that. I am running with one of the relays pulled so that the fan runs full-time.

I am SO tired of everything needing to be controlled by the computer on modern cars! Even things like turning the KEY to start the engine don't just close a relay anymore... No, that key signal ONLY goes to the computer, which then decides whether to allow the engine to crank or not. If your airbags deploy (or you buy a boneyard ECM from one that did) you can't even check the computer by starting the engine - The computer won't allow the starter to even CRANK if it thinks the airbags went off! I guess this is a "safety" design, to force you to tow it to a dealership who can reset your wallet.

tjkj2002 · **Posted:** Thu Apr 28, 2011 4:38 pm

geordi wrote:

I I am SO tired of everything needing to be controlled by the computer on modern cars! Even things like turning the KEY to start the engine don't just close a relay anymore... No, that key signal ONLY goes to the computer, which then decides whether to allow the engine to crank or not. If your airbags deploy (or you buy a boneyard ECM from one that did) you can't even check the computer by starting the engine - The computer won't allow the starter to even CRANK if it thinks the airbags went off! I guess this is a "safety" design, to force you to tow it to a dealership who can reset your wallet.

That is totally false,the PCM has nothing to do with the airbag system besides suppling some info for the SRS module like speed,brake applied,and other info.Will not cause a vehicle from starting if the airbags deployed.I worked in a bodyshop and can varify I have never had a vehicle not start if the airbags deployed,of course if the engine compartment was not damaged enough to hinder proper operation like the radiator pushed into the fan.

No resetting ever done,can not be done either.

JL Rockies · **Posted:** Thu Apr 28, 2011 4:39 pm

Yes... now that you mention it, my fan does kick on hi for a brief moment when I first plug the relay back in. I guess you could just hack into the fan harness and add a manual switch and diode-isolate the circuit so the computer doesn't get all whinney.

Joe Romas · **Posted:** Thu Apr 28, 2011 4:50 pm

Page 8W-30-18 for the 06 CRD shows the high and low relays are controled by the engine control module. I would start by reseating the ECM plugs :SOMBRERO:

I don't see anything in the relays that would cause your condition.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The electric fan has several inputs for the relay control including vehicle speed, ambient air temp, AC head pressure, transmission fluid temp, fuel temp and coolant temp. Usually with the AC on max fresh air the head pressure will cause at least the low speed fan to turn on.

geordi · **Posted:** Thu Apr 28, 2011 5:31 pm

tjkj2002 wrote:

That is totally false,the PCM has nothing to do with the airbag system besides suppling some info for the SRS module like speed,brake applied,and other info.Will not cause a vehicle from starting if the airbags deployed.I worked in a bodyshop and can varify I have never had a vehicle not start if the airbags deployed,of course if the engine compartment was not damaged enough to hinder proper operation like the radiator pushed into the fan.

No resetting ever done,can not be done either.

You may have spent time huffing paint in a body shop, but that doesn't give you experience that trumps a real-world situation.

I purchased a boneyard ECM from a CRD that had blown airbags. I have no clue about the rest of the status of the engine / vehicle, as the engine was not present in the shell that the yard had.

HOWEVER - I do know what the CRD will do when the SKREEM module and the ECM don't agree about what the keycode is: The engine will crank and start as normal, but will be shut off within 2 seconds. This boneyard ECM would only allow a 1/2 revolution of the engine from the starter, then the starter would not engage again. Cleared the codes from that ECM, same result. The codes were just the usual "MAP / MAF problems, EGR failure" from a high mileage fully-stock CRD. The test bed was in MY WORKING CRD, which I had driven to the boneyard to purchase this boneyard ECM. Once I put my own ECM back in, the engine started instantly.

There were no other codes in any other system when the boneyard ECM was plugged in - ABS / airbags / BCM etc were all clear. Yet the boneyard ECM would not allow the engine to crank.

The ECM was subsequently sent to GDE, who was able to re-stock the program, and sent to Sebastian in Argentina who is now driving around on it.
THE COMPUTER WAS NOT ALLOWING THE ENGINE TO CRANK because the airbags had been deployed.

tjkj2002 · **Posted:** Thu Apr 28, 2011 7:29 pm

geordi wrote:

tjkj2002 wrote:

That is totally false,the PCM has nothing to do with the airbag system besides suppling some info for the SRS module like speed,brake applied,and other info.Will not cause a vehicle from starting if the airbags deployed.I worked in a bodyshop and can varify I have never had a vehicle not start if the airbags deployed,of course if the engine compartment was not damaged enough to hinder proper operation like the radiator pushed into the fan.

No resetting ever done,can not be done either.

You may have spent time huffing paint in a body shop, but that doesn't give you experience that trumps a real-world situation.

I purchased a boneyard ECM from a CRD that had blown airbags. I have no clue about the rest of the status of the engine / vehicle, as the engine was not present in the shell that the yard had.

HOWEVER - I do know what the CRD will do when the SKREEM module and the ECM don't agree about what the keycode is: The engine will crank and start as normal, but will be shut off within 2 seconds. This boneyard ECM would only allow a 1/2 revolution of the engine from the starter, then the starter would not engage again. Cleared the codes from that ECM, same result. The codes were just the usual "MAP / MAF problems, EGR failure" from a high mileage fully-stock CRD. The test bed was in MY WORKING CRD, which I had driven to the boneyard to purchase this boneyard ECM. Once I put my own ECM back in, the engine started instantly.

There were no other codes in any other system when the boneyard ECM was plugged in - ABS / airbags / BCM etc were all clear. Yet the boneyard ECM would not allow the engine to crank.

The ECM was subsequently sent to GDE, who was able to re-stock the program, and sent to Sebastian in Argentina who is now driving around on it.
THE COMPUTER WAS NOT ALLOWING THE ENGINE TO CRANK because the airbags had been deployed.

Incorrect sentry key code and VIN # was your issue not a SRS issue.

JL Rockies · **Posted:** Thu Apr 28, 2011 7:34 pm

You thread-jackin' bastids.... :lol:

Wobbly · **Posted:** Thu Apr 28, 2011 8:18 pm

GreenDieselEngineering wrote:

The electric fan has several inputs for the relay control including vehicle speed, ambient air temp, AC head pressure, transmission fluid temp, fuel temp and coolant temp. Usually with the AC on max fresh air the head pressure will cause at least the low speed fan to turn on.

Where are the control settings and/or diagnostic procedures listed? The FSM refers to a diesel diagnostic manual. Is that available?

warp2diesel · **Posted:** Thu Apr 28, 2011 9:09 pm

When I had AC/AC fan problems and the relays drove me nuts, it turned out to be a loose harness plug near the TCM I bumped when I swapped my TCM. Pushed it back together and all came back to life. Too bad I wasting hours to figure it out with the FSM and my AC gauges too. If you have gone anywhere near the TCM or other stuff on that side, press the three plugs together.
Good Luck

Jacked-up condesnsor fan operation

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