So mine was leaking slightly so decided to change it you know the tricky one under the battery anyhow all fitted was running the car to temp to get the fans to come on so I knew the sensor was working but they never kicked I checked fuses and fine anyway to do a proper test obviously  after just changing my head gasket I don't want to over heat the car and ruin all that hard work.

Take the car for a 15-minute plus drive on a hot day and then park up with engine idling. If the thermoswitch (and fans)  are working the fan(s) will come on at low speed shortly after, probably only for a short time though.

Does the car have A/C? 

Yes it does have ac mate.

Then checking that the fans themselves work at low speed is as simple as switching on the A/C, turning the dial to cold and waiting for a short while to see what happens under the bonnet.

 

You almost certainly could have fixed the leaky thermoswitch by tightening it up a touch, but never mind. A/C cars' thermoswitches don't carry the fan motor currents, just the relay coil currents, so virtually never fail.

The wiring to them can be vulnerable though, as it's very thin. 

Edited 1 June, 20215 yr by Wino

Ah right good to know thanks wino.

So I ran engine for about 20 mins eith ac set on cold but fans never kicked in any ideas ???

Which fuses have you checked?  I'll just look up which are the right ones on your car.

Edited 1 June, 20215 yr by Wino
sp

All these are in the engine bay fusebox.

Strip fuse no.5 - 40 amp rated

Blade fuse no. 8 -  30 amp

Blade fuse no. 11 -  5 amp

 

The last two are under a clip-on cover to the right of the strip fuses, you'll see wiring to them, but not the fuses themselves 'til you unclip that cover.

got you I did check the strip fuse as this blew before ages ago I will just pop and check those other 2 

All good now thanks wino was fuse 8 I always forget about those hidden ones lol thanks mate 

Do both fans come on at low speed now when A/C is switched on?  

 

Oh did not try that after fuse changed I let it run hot and the fans came on should I still do that as well now then ???

No harm in trying it, but if they both came on with radiator getting hot, I'd expect them to both come on via the aircon action too, unless the A/C isn't working for some other reason.

Yeah true I will try it and let you know ac should be good I only regassed it 3 months ago.

Ok so run the ac this morning on cold full blowers for about 15 mins fans did not come on then run it same but on hot still did not come on but i can hear the compressor kicking in and i had the valve on ac and there is plenty gas in it and it was cooling down but still no fans on low speed.

Do you happen to know the correct psi my guage should be reading for the coolant pressure ???

47 minutes ago, Stewartasb said:

Do you happen to know the correct psi my guage should be reading for the coolant pressure ???

Hi Stewart, check if the operating relief pressure is marked on the coolant system cap, system operating pressure should be a little lower than that - I'd take a guess at around 1.5-2.0 bar. 

2 hours ago, Stewartasb said:

Ok so run the ac this morning on cold full blowers for about 15 mins fans did not come on then run it same but on hot still did not come on but i can hear the compressor kicking in and i had the valve on ac and there is plenty gas in it and it was cooling down but still no fans on low speed.

 

Check that fuse 8 hasn't re-blown as a first step.

 

My experience with VCDS suggests that once the refrigerant pressure sensor in the high pressure line reads 9 bar, the fans come on at low speed. If it then dips down below 6.8 bar, they go off again. And cycle on/off as reqd.  If the pressure ever gets up to 16 bar, the fans switch to high speed (if they are both twin speed). Back down at 12 bar, from memory.  1 bar is approx 15 psi, so multiply those numbers by 15 to get psi.

Edited 2 June, 20215 yr by Wino

Ah I think my refridgerant pressure may be low based on what you said needs more gassing it seems which might explain why they not kicking in will add some more gas and let you know the outcome 

4 hours ago, Stewartasb said:

will add some more gas and let you know the outcome

Alternatively, you could get someone who actually knows what they're doing to work on it, rather than:-

1. Breaking UK law by doing it yourself.
2. Making a larger hole in the ozone layer by DIY.

Erm firstly this is a help site and I'm perfectly entitled to work on my own car and secondly before you go flapping your gums without knowing the facts this car had no gas in it when I got the car so all I've done is put some in so I've not helped destroy the ozone layer so kindly keep your unwanted comments to yourself if all you can offer is low level sarcasm and unsubstantiated accusations KEN.

And also KEN the law is based around the extraction and safe disposal of old refrigerant I'm breaking no laws by adding it or working on it.

11 minutes ago, Stewartasb said:

this car had no gas in it

Why? I'm going with "because it had leaked out". Unless you actually know that this leakage was natural wastage, then there could be a leak in the system, which you (based on your account) have made no effort to test for.

 

Oh, and UK statute law is matters of fact, not changed by accusations of sarcasm or a belief in your own superiorty..

3 hours ago, Stewartasb said:

Erm firstly this is a help site and I'm perfectly entitled to work on my own car and secondly before you go flapping your gums without knowing the facts this car had no gas in it when I got the car so all I've done is put some in so I've not helped destroy the ozone layer so kindly keep your unwanted comments to yourself if all you can offer is low level sarcasm and unsubstantiated accusations KEN.

In which case you have wasted both your time and your energy, because at the very best your system will contain at least a 25% moisture laden air the water content of which will have condensed with the pressure of the refrigerant gas that you have introduced. Probably more like 50% given the low refrigerant pressure you seem to have.

 

I am making the assumption that you have not invested in a vacuum pump (which would have told you that the system had a leak) and A/C guage set plus a cylinder of R134a gas (only available to licensed professionals) and have used some Chinese top up canisters labelled R134a but in tiny print saying "eco alternative" which will turn out to be propane gas.

Edited 2 June, 20215 yr by J.R.

14 hours ago, Stewartasb said:

Do you happen to know the correct psi my guage should be reading for the coolant pressure ???

 

Nobody can answer that as the high side pressure is dependant on temperature and humidity, the low side pressure is directly proportional to temperature but a very crude way of checking if the system has the correct charge.

 

You will need to study some graphs on the interweb to see what your pressures should be, if you are measuring using VCDS be aware that it reports absolute and not guage pressure.