Any way to test out the cooling fan module?

[rx6180]

My car is a 1999 W202 C200 and I'm confused as to whether my radiator cooling fan module is working properly or not. Last week on a warm sunny day, stuck in town traffic I got the feeling that my temp gauge needle had crept a little higher than normal with no effort from my cooling fan. Back home I lifted the bonnet and let the car idle and watched the fan. At one point it gave a little kick then stopped. I risked life and limb by spinning the blades and then the fan kept running, at a slowish speed. My feeling was that is should be running faster. Then I stopped the engine but turned the ignition straight back on, expecting the fan to still run but it did not and didn't want to know if I flicked it by hand. Later in the evening I drove the car to warm it, then sat in a car park waiting for the engine temperature to rise to start the fan again. After 15 minutes or so the engine temperature seemed to have reached its zenith and would go up no higher - it was a cool evening - but at an estimated 95C on the gauge (below the line underneath the line marked 120C) the fan still showed no interest. Having discovered from my workshop manual and the internet that the cooling fan runs if the air con is switched on, I put the air con on yesterday on a short trip (I hardly ever use it) and when I got home the fan was turning at lowish speeds. I switched off the air con, then on again - and the fan would not restart. Is this normal? The air con is nearly out of gas and I wasn't that bothered because I don't use it much, but could the lack of gas affect normal function of the module even if the air con is turned off? I've checked the fan motor, off the car, with a spare 12v car battery and it nearly took off, so no problems with that. I was wondering if there were an ways to 'frigg' the module to test it out other than having to let my engine get really hot! And I suppose it isn't beyond the bounds of possibilty that a faulty module might work sometimes a little bit, and then not at all. My interior heater/air con module was like that when I bought the car almost 8 years ago.

 

[television]

OK when the engine gets to 3 degrees over the thermostat opening temp about 90c on your car, the visco coupling engages and the fan runs at full speed, if the visco is OK the fan blades should slice a carrot.

Now it is possible that the hot spot in the rad is blocked preventing the hot air from triggering the bi metal strip that engages the clutch on the Visco coupling

 

[rx6180]

Its an electric fan though, not a viscous coupling.

 

[television]

I miss read that,, the rad fans are mainly used for the air con and you probably have the 2 stage set up in your car,, that temp of 95c is ok though not much higher

 

[rx6180]

Hmm. My feeling about the thing is inconclusive. In town on Saturday I was convinced the fan wasn't coming on when it used to do, but I didn't overheat. Since then I've not been able to force it to run properly by running the car at idle. I'm going to the Goodwood Revival in a couple of weeks and there's usually a long queue to get in and I'll need my fan, but neither do I want to purchase a new 'module' if it isn't necessary. And of course a computer diagnostic at a dealer will probably cost me £90 or more for nothing much at all.

By the way, Malcolm, your comment about manual locks - I've never tried my door lock but my boot lock is non operative. My car alarm usually sounds in the night at about 4am about three times a year, usually when its stormy, and my cure is to get up out of bed, unlock it then manually lock the doors from inside, finishing with the rear door. This disables the alarm. But I realised the boot stayed unlocked. I tried to lock it manually and I'd got no chance. No amount of WD40 made any difference. It's beyond redemption.