Radiator fan only turn on at over 100°C

[Eskozki]

Hi,

Noticed that my rad fans are blowing the wrong way because PO has messed with the wiring. It also looks like my -87 car has an early thermoswitch ie. Only two wires with spade connectors. Could this be the cause as the late style should have a two stage switch? The late style plug is also missing so perhaps the switch is original? Didnt see anything left of the plug while I was under the car.

[944 Ecology]

Yes, the radiator fan wiring is a bit complicated. Any changes to the factory setup will result in less than adequate performance. Do yourself a favor and return it to the stock configuration as soon as you can.

[walfreyydo]

You should test the relay as shown on clarks (see the bottom of the page). If the relay checks out as OK, then its the fan temp switch (should be 3 prong to match the connector for the relay). There are different temp switches, so make sure you get the one that matches the thermostat. I *think* 85/93C is the one you want but not 100% sure. You are correct that late model is a two stage fan temp control switch (low/high speed fan operation)

Cooling Fan Operation and Troubleshooting

[Eskozki]

Thanks for the link, going to buy the correct thermoswitch and try to figure where the old wiring has gone. Other rad fan now spins the correct way. It was wired with two regular spade connector so just had to switch those around. Other one has the original connector in place so I can't that easily change that, need to find where the PO has made his own wiring. But atleast with one fan blowing correct way the engine now cools. I think the fans blow only on high speed now even with ignition off. I'm quessing PO hooked up the thermoswitch so that it goes through the highspeed side of the relay.

[Eskozki]

Well... the 2-pin connector for the wrong type of thermoswitch goes to the original wiring harness, there is no extra wire left put fo the 3-prong switch. Clarks had a wiring diagram so not all is lost, just need to figure out how to rewire. But this seems like my car has originally had the 2-prong switch, wonder if anyone else has come across with similar story. Maybe my car was made from whatever was left on the production line ��

Not the only thing that should be in an early car but has found its way to my -87

[walfreyydo]

When you say 2-pin connector - Are you referring to the plug that goes to the actual fans, or the plug that goes into the actual thermo switch? The thermo switch is a sensor that screws into the upper part of the radiator just below the upper coolant line (its hard to get to). Based on the year of your car, that plug should be a three prong plug as outlined in clarks.

It seems crazy that someone would rewire that plug AND the relay to be a 2 prong plug.

I just want to be sure we are both talking about the same 3 prong plug which plug into the actual temperature sensor ie: thermo fan switch

Could you post a photo of the two prong plug and its location?

Another way to confirm this is whether BOTH fans run when hot (both fans can run high and low speed, this is late model), or just one fan runs (one for low and one for high, this is early model)?

[Eskozki]

Both fans run when the switch closes at 102°C and continue to run even with ignition off until the switch opens again at 92°C. I think they run only low speed because the fans are pretty quiet when they run. I took a photo of the switch, the two brown wires are the wires going to the switch.

[Eskozki]

No red/white wire either at the relay end. As the wires going to thermoswitch are correct colour for the late model Its a bit weird. Like someone deleted the whole wire from the harness for some idiotic reason. Wired a switch from the TS terminal of the relay and now I can atleast toggle full speed fan when I want/need to.

[walfreyydo]

One of the terminals is the high speed signal, and the other is the low speed signal (the third is ground). If the PO removed one of the wires, that would mean you are either not getting high speed fans, or low speed fans.

However, part of me also suspects you may not have the correct switch identified. You are 100% positive you have located the fan control switch?

Your photo shows two wires leading into something (cant make out where it is). There is a 3 slot connector that should plug into the switch which I am not seeing in this photo - leads me to believe you dont have the correct switch identified.

Can you post another photo showing where in the engine bay your switch is located? Again, it is a round sensor that screws into the top part of the radiator just below/next to the upper rad hose with a 30mm(?) socket. It looks like this:


The other possibility is the PO installed a (incorrect) 924 temp control switch and just disabled your high (or low) speed fan.

Here is a picture of its location - right side of engine bay top of radiator directly next (right) of one of the fan guards. Note that the upper radiator hose is removed in this picture for clarity and the hose junction is blocking the view of the actual sensor.

[Eskozki]

There is so much stuff in the way it is impossible to take a better picture, but it is the thermoswitch, if I put those two wires together, rad fans start running slow speed. My picture is upside down, you can see the fan on the left and upper rad hose. 3-slot plug is missing from my car and when I tool the fusebox out, there was no red/white wire there either on the connector for the relay. So now my fans operate slow speed through the thermoswitch and fast speed through the switch I wired to the cabin.

[walfreyydo]

Ok so to me it sounds like someone replaced the 3 slot temp switch with a 2 slot temp switch from a 924 (or early 944), and simply disabled your high speed fans by cutting the wire.

Thats pretty ridiculous if someone did that.

If you can trace back to your fan relay, you could re-run that third, high speed fan wire back and re-install the three prong plug and switch. Hopefully your fan relay is still intact- Im guessing it should be since high speed is manually operable.

That should solve your issue. Youll just have to find a replacement plug, install the correct thermo fan switch, and run a new wire from the relay to the switch and install it (and the other two wires) in the 3 prong plug.

Some good info here for reference:
http://www.clarks-garage.com/shop-manual/cool-01.htm

[originalowner]

I have a hard time imagining that the PO actually removed the wire from the harness. More likely just clipped off both ends. If you unwrap the cable a few inches, you may be able to splice new ends to reconnect it.

[Eskozki]

I unwrapped the cable at the thermo switch end and didnt find any traces of the wire, I would need to cut some of the harness protection to look further. On the relay box end it is pretty crowded and didn't see any traces of it either. Most of the DIY electric stuff has been made very poorly so it boggles my mind why this wire seems to be completely erased.

[originalowner]

Also, looking at your year's schematic, there is a pressure switch in the A/C system that also grounds the missing wire. Since the wire is missing at the relay, this function is disabled in your car as well. The pressure switch should ground the high speed signal terminal on the relay in order to increase airflow over the condenser if the pressure gets high enough. Early cars always run the fans at high speed with the A/C compressor on, so they must have implemented this on later cars to reduce noise when high speed is not needed.

If you can't find the wire on the lower end of the thermoswitch cable, you might be able to jumper over to the pressure switch (wherever it is, my early car doesn't have one) to get the signal up to the relay end. You're still going to have to splice it on the upper end.

If you end up running a whole new wire, be sure to run the relay to both the thermoswitch and the pressure switch.