troubleshooting engine cooling fan

casual friday · Post by **casual friday** » 25 Jul 2012, 05:04

I don't hear my auxiliary fan turning on anymore. Anyone know how to diagnose whether it's the fan itself or the relay that has failed?

Thanks in advance.

Post by **Ozark Lee** » 27 Jul 2012, 21:02

You can hot wire the red wire to the fan directly to the + battery terminal - if it runs at full speed the fan is OK.

From there try individually grounding the yellow wire and the yellow wire with the white striped that connect to the center connector on the fan relay. The connector will be need to be plugged in for that test to work.

One will run the fan at low speed and the other will make it run at high speed. I can't remember which wire color controls which speed but you will hear the difference. If the fan doesn't run then the relay is bad.

...Lee

Post by **Pauloil** » 28 Jul 2012, 06:56

if the fan is bad, you can work it out of there after removing 2 upper torx, either T20 or T25, and then loosening the 2 lower ones. while you have it out, replace the positive battery to starter cable.

http://www.ipdusa.com/products/8373/113 ... ng-fan-850

http://www.fcpgroton.com/product-exec/p ... To+Starter

fcp may have the fan cheaper

casual friday · Post by **casual friday** » 29 Jul 2012, 15:19

Thanks to both of you for the info.

Lee, do you mean the red wire that goes into the relay?

Post by **Ozark Lee** » 29 Jul 2012, 20:27

I really should have been a bit clearer on that since there are two different red wires involved. The Red wire and the Green wire that go to the fan itself are the ones to test the fan motor. I think the Red wire is high speed and the Green wire is low speed on the fan. Feed each of those wires + battery voltage to verify the fan is working. The Yellow and Yellow/White wires are the wires that activate the relay to come on either at low speed or high speed and they are triggered by grounding them. To do that test I just shove a paper clip in the back side of the connector and then use a piece of wire to ground the paper clip.

The red wire that goes to its own connector to the relay is the battery voltage that feeds into the relay.

...Lee

Post by **scot850** » 22 Aug 2016, 13:59

Re; Fan relay testing. Electrics are not my strong point, so I have a couple of additional questions to Lee's helpful instructions on how to test.

To test the fan motor, I believe you split the connector on the clip at the back of the fan shroud and power the 2 connections respectively from there with the ignition off.

To test the relay I understand the principle of the grounding of the relay input terminals to activate the relay, but is this done with the ignition on as the feed is presumably off until then?

I am not getting the 'jamming a wire paper clip into the back of the connector as the 2 wire connections look sealed. Is this not the case?

Many thanks,

Neil.

Post by **scot850** » 22 Aug 2016, 15:03

Followed Lee's info and tested the fan motor for both speeds. Made up a wire with clamps on both ends and connected directly to live (red) on battery and other end to an electrical small screwdriver and poked in at both contacts. All good on the actual fan. To test the fan I used the 2 contacts on the wire with the grey larger connector that has the 2 wires that run down to the fan from the right (as seen from standing in front of the car looking down).

: Cooling fan relay connector cables

: Cooling fan relay removed

I still have to check the relay itself, but need guidance how to poke the paper clip into the relay input for fan speed, and also confirmation the ignition has to be on. The 2 wires to the input connector have plastic shrouds around them and they look sealed.

Finally, should the fan continue to run after the engine is switched off (on both turbo and NA cars) and if so, what are the deciding factors the car uses to determine this?

Thanks,

Neil.

Post by **Ozark Lee** » 22 Aug 2016, 17:14

The seals at the back of your connector are in well above average condition so, in your case, I would avoid disturbing the seals at the back of the connector. In most cases those seals are pretty loose and you can easily shove a paper clip in to make contact with the pin on the connector. You can accomplish the same thing by using a wire from any ground point on the chassis to the individual terminals on the relay that the center connector plugs into.

The behavior of the fan after the car is shut off varies. Sometimes it runs on for a short period of time if it is very hot and the air conditioner has been in use but usually it doesn't. The determining factors are engine temperature and also how long it takes for the high pressure side of the A/C to equalize. Waiting for the A/C to equalize is usually less than 5 seconds.

If it runs on for more than about 30 seconds then I would suspect a bad ECT sensor since that is one of the typical behaviors when the sensor is out of range.

...Lee

Post by **scot850** » 22 Aug 2016, 17:26

Thanks Lee. So just for clarification, I need to:

1) Disconnect the middle (IN) connector (do that first before switching the ignition on).

2) Have the ignition on to II position to power the relay via the RED connector?

3) Connect a ground wire from any good ground to either of the IN pins, and this will confirm the relay is operating correctly on both speeds (even with the connector still disconnected for this purpose of testing).

If both connectors pins operate the fan (1 for each speed) the relay is good.

Have I got that correct?

Thanks,

Neil.

Post by **Ozark Lee** » 22 Aug 2016, 20:45

That will work. I think the red wire is always hot, at least it is on an 850. On a 70 series I'm not 100% sure but my guess is that it always is hot as well so that the fan can continue to run after the key is removed.

...Lee