Electric Cooling Fan won't come on.........

[HoseHead]

'90 SC auto
- Cruising along, temp gauge goes past "M", check gauge light comes on, stop car - cooling fan not running.
- Tow car home, water pump weeping through hole. Replaced water pump, thermostat etc.........no coolant in the crankcase....Whew!!
- Car runs excellent with a steady 20 inches of mercury @ idle.
- Cooling fan still will not come on and I have to shut the car down to prevent an overheat.
- fan unit proven serviceable in another SC. Functions perfectly.
- fan controlled by EEC-IV - gotta pull codes using analogue multimeter (the Haynes Manual also indicates failure could be in the "Integrated Relay Control Module" located behind the right headlight).
- hook up meter and get a constant 12 Volts between the SelfTest pin and signal return pin 2 on the SelfTest connectors - Why?
- the meter should show open and sweep for codes when key is turned on Any ideas out there?

Bruce

[Jason Wild]

Bruce,
There is a fuse for the Rad fan that could be the problem.
If not the IRCM might be the problem I had mine once say on. One hit on the box and off it went. Might want to try swaping it out with one from a working car the 93 will not work.
The other thing I would try is the Temp sencer by the DIS I know that can be a problem as well.

[Tubeamp]

I would have to agree. Those IRCM's can be something of a pain @ times...

If you can, borrow one off a friend and give it a try.

Rino

[Payton]

I would have to agree. Those IRCM's can be something of a pain @ times...

If you can, borrow one off a friend and give it a try.

Rino
I know what you mean, Rino. I have your car;) :eek: I guess you gave up chaising this problem around and simply ran a switch to under the dash?)))

[MercsSC]

did you try turning the A/C to MAX {button} fan should run... if A/C is working...next unplug ECT{coolant sensor} by DIS .. turn ignition to run position and fan should run ....if water pump was leakng coolant... it may not of been able to reach sensor ..due to air in the system ....really have to purge the system to get the air out after draining coolant ....dave

[HoseHead]

Thanks guys. I'm still persuing. The car runs perfect and stays cool when I run the fan continously, bypassing the IRCM using a jumper.

The IRCM relays are not energizing. The EEC provides this signal on Pin24, a Red wire. Stand by.....

Bruce

[Paul93SC]

The IRCM is a bunch of relays all housed in one box, and while that may not be a revelation, all of the symptoms relays suffer from are the same. And, the most common relay failure mode is burned out contacts.

I don't think pulling codes is going to help here Bruce. You're going to have to pop the hood and start probing around the system with a voltmeter in order to find out where the fault lies.

The most common "overlooked" fan failure is the 16ga fuseable link wire. These burn up and will not provide the necessary current for the fan motor, however it will pass voltage under a "no-load" test. It's important to keep everything connected properly while testing voltages at various points in the system.

Check out the simplified diagram I submitted a while back. It will help you understand and track down which part has failed.

http://www.sccoa.com/forums/attachment.php?attachmentid=15689&d=1128271204

Also, do a search on these forums... you'll be overwhelmed by the amount of info on this particular subject! :eek:

[HoseHead]

Thanks Paul. I like that diagram as it shows voltages, but it is for a '93. The car I'm working on is a '90. I believe the relay pinouts are different between these years, but the IRCM functionality is the same.

1. All 12VDC inputs to the IRCM function correctly in their specific modes - Hot all the time or when the igintion is on.

2. With car running - If I place a ground on Pin 17 (Pink wire) (EEC High) the fan functions fine, so that relay is good.

3. With car running - If I place 12VDC on Pin 14 (Tan/Orange Wire) (EEC Low) the fan functions fine, so that relay is good.

The IRCM appears to be sound. It appears the EEC is not providing the correct voltage (or ground as applicable) to the IRCM inputs.

It could be the 16ga fuse link as you've indicated. Do you know where this one is physically located on the car?

I'm working on this intermittently throughout the day. '"m married so only get weekend minutes of personal time. Now I'm off to box seats for the Sens/Lightening game. Thank God for vendors with coin. How's Toronto doing in their series so far? :)

Thanks for your time.

Bruce

[phyxius]

Bruce if you want to try a working ircm let me know i can run you down my spare i have or wwe can try the one on my car.i have to go to ottawa tuesday evening so i can stop on my way by let me know.

[Paul93SC]

If you take another look at my diagram, you'll see I carefully omitted pinout #s on the IRCM :D (I gave pinouts for the EEC though).

The IRCM appears to be sound. It appears the EEC is not providing the correct voltage (or ground as applicable) to the IRCM inputs.Then I would look at a faulty ECT sensor as a potential cause. If you have an ohm-meter, measure the resistance on the two ECT sensor pins: you should measure ~30,000 ohms @ 20c, or in your case ~55,000 ohms @ 10c (Ottawa is always a bit colder right? :D ). Next would be to carefully inspect the passenger-side electrical harness for damage, partially un-plugged connectors, etc.,.

It could be the 16ga fuse link as you've indicated. Do you know where this one is physically located on the car?Don't worry, you can rule the link out as the culprit because the fan worked when the proper inputs were provided to the IRCM.

[HoseHead]

Then I would look at a faulty ECT sensor as a potential cause. If you have an ohm-meter, measure the resistance on the two ECT sensor pins: you should measure ~30,000 ohms @ 20c, or in your case ~55,000 ohms @ 10c (Ottawa is always a bit colder right? :D ). Next would be to carefully inspect the passenger-side electrical harness for damage, partially un-plugged connectors, etc.,.

Thanks Paul. I had already ruled out the link after looking back at the schematic and plugging in voltage findings from tests. Currently, I have the fan low speed shorted to run whenever the ignition is turned on. Car runs quite cool now, but am sure this fan was not designed to run continously and will swap out the IRCM from my '90 XR7 this weekend as it is at the cottage right now. In the interim. I will meter the ECT sensors as you advised. Harness and all connectors have been inspected without any visible issues detected. Cheers.

Bruce

[HoseHead]

Bruce if you want to try a working ircm let me know i can run you down my spare i have or wwe can try the one on my car.i have to go to ottawa tuesday evening so i can stop on my way by let me know.

Brionne,
Your offer is appreciated, but it's already Tuesday and I'm booked to the teeth. This car is not a daily so I do have the luxury of time to resolve this issue. We will get together soon. Cheers.

Bruce

[Payton]

It appears to be one of the common problems with our cars. Like I said, I had the same symptoms last year. After trying to chaise it around the car I ended up buying a Zirgo adjustable fan switch, which turns fan on when coolant tempeature reaches 180-240. :o

[phyxius]

well if you ever need a hand or want to try my spare ircm let me know i'm only a half hour from the prior and go to A&O all the time.