Mikemt68

Auxiliary fan not working

16 posts in this topic

Hey guys, back again. 96 eldorado, just got a check engine light, got home and checked the codes and it was p1660. While I was driving temp is fine but when I stop it goes up, I leet the car sit in the driveway and let it heat up the fan is not coming on. I was wondering if anyone has some tips on how to check for the problem. Thanks

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Are the fans coming on when the A/C in turned on?


THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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See this thread it may be helpful,.it is also a P1660

 

 


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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@OldCadTech, when I bought the car one of the aluminum lines for the ac was in the trunk u put it back on but have never used the ac. I will turn it on and see if the fans come on

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That's right, forgot about that, sorry. You know I go to sleep & ........

It is a method to test the fans without scraping or burning your knuckles. The PCM commands the fans on with the A/C on... But since yours is out of refrigerant that won't work.

Make sure that the relays are all connected. There are 3 relays mounted on the bottom of the core support. You can swap with a known good one. They are notorious for failing.

To test the fan, you can run a (+) & (-) to the fan motor. You can get a connector from the junk yard or make up one yourself with some same gauge wire. OR you can remove the fans and test them, that is a PITA tho.

To verify that the PCM is controlling the fan, you can try disconnecting the connector at the fan motor and connect a wire to the ground wire at each of the connectors, but you have to plug the connector back in because the PCM controls the ground for the cooling fan. So you will have a wire running from the connector up to where you can access it when the engine is hot. I don't recall if the cooling fan hot side was hot all the time with the key on but you can test that when you disconnect the connector.

Run the engine at idle, when the coolant temp indicates 225 or higher and if the fan is not running, touch the test lead ( momentarily ) to a good ground.

Did you check the PCM connectors? Makes me wonder a little about the PCM after the A/D code. Did you clear the codes and see if any codes came back?

I think @BodybyFisher has a FSM for 96, so he may have a schematic...


THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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@OldCadTech  what schematic does he need?


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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@OldCadTech I did clear the codes and it came right back, I am going to go and check the connectors, In a bit have to move some vehicles around in the driveway and garage to get the caddy in. THanks guys

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2 hours ago, BodybyFisher said:

@OldCadTech  what schematic does he need?

The cooling fan circuit.


THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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CoolingFanPage1.jpg

CoolingFan2.jpg

Mikemt68 likes this

Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thank You BBF :)

I have appointments this am and office time but at first glance the PCM controls the fans and fan speed thru the relay grounds and a potentiometer in the PCM.

I had a much different cooling fan diagram in mind. SO, the previous post, except for the fan tests themselves won't work. You will have to test at the relays. More on that later but check the red wire at the relay for power it should be HOT at all times, so you can check it with key off.

Be sure to check the PCM BLUE and CLEAR connectors & the 50 amp cooling fan fuse first.

 


THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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The PCM should "see" the fans drawing current, does that make sense?

Have you tried putting 12 volts directly to each fan to see if they run?  Be sure to disconnect the connector when you apply voltage to the fan.

By the way, for $50 Jake from NP can mod the PCM to turn the fans on earlier!  I like that idea.


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Posted (edited)

@BodybyFisher  No, the PCM monitors eng coolant temp. It will turn on the cooling fans and vary the speed of the fans accordingly. If it sees the coolant temp continue to rise it will command hi speed for both fans, if the coolant temp still continues to rise it will turn the engine temp light on and set the code. The PCM assumes the fans are running, there is no feed-back circuit.

Edited by OldCadTech
BodybyFisher likes this

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Thanks guys, I am at work today also, i will get back to you all as soon as I can..much appreciated! 

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Posted (edited)

@OldCadTech and @BodybyFisher, finally tore in to this and turns out I had a blown compressor fuse. Found this out after checking the connectors, I took a light to the maxi fuse for the fans and just started to check the others around it, once I replaced that fuse I started the car and let it warm up and the fans kicked on. I reset the p1660 code and the engine light went off and after about a half hour ride everything seems OK not over heating and no more code. Does that seem right to you guys? Would that fuse have an effect on the auxiliary fans? Thanks

Edited by Mikemt68
BodybyFisher likes this

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Yep, it sure does make sense. The A/C clutch fuse is eventually spliced into the relay power or "hot" side. Eventually, to the PCM for control of the fan speed.

Good job, Gotta love a story with a happy ending. :shaka:

 

Mikemt68 and BodybyFisher like this

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Thanks for the help again, what a great place !

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