radiator fan thermoswitch COOLING PROBLEM RESOLVED

[STORM 2 0]

Hi everyone

Am I correct in thinking the radiator fan thermoswitch only controls the fan during driving and is not responsible for fan 'run-on' (when ignition is off)?

[serious overheating problems during driving - have already replaced the aux coolant pump and flushed out the system today - to no avail]

 

cheers

[RW1 0]

Fan run-on with ignition off is one half of the yellow sensor in the themostat housing.

 

The thermo switch - two temps for general driving is the one half way down the black rad plastic end piece on the battery end with thick red wires going to it. If driving, cooling in the main is just airflow pushed in by the car moving but the fan should operate if slowing from higher speeds or standing traffic and it depends on conditions.

 

If you are saying it is overheating while on the move, then the suspect may be the thermostat (ie. not fully opening). Check how hot the radiator on the two connection pipe to the engine. Both should be hot when the engine is warmed up.

 

Also, check the water pump pulley is rotating although I would have thought you would hear it squealing if stopped. Not conclusive th ewater pump is OK but it's a quick confidence check before getting serious on it.

 

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[STORM 2 0]

HI

the fan doesnt run at all whilst the ignition is on but will run once it is switched off.

I assume the switch located on the rightside (looking from the front of the car into engine bay) of the radiator is the thermoswitch for 1 and 2 fan running (ie not after run)

Am I correct in thinking the thermostat (housing) you are thinking of is located beneath the coilpack. would you replace all of this --its quite a large part with plenty of connectors on it.

 

My idea was to replace the thermoswitch on the radiator - but if this was faulty would the fan still work on 'run-on'?

 

NB I WILL CHECK THE TOP AND LOWER RAD PIPES TOMORROW AND POST AGAIN

[RW1 0]

I assume the switch located on the rightside (looking from the front of the car into engine bay) of the radiator is the thermoswitch for 1 and 2 fan running (ie not after run)

 

Yep.

 

My idea was to replace the thermoswitch on the radiator - but if this was faulty would the fan still work on 'run-on'?

 

Yes it would as the yellow sensor in the thermostat housing runs that bit.

 

First check the fuse 19 ( 30amps ) on the fuse panel in the driver's side footwell. Then check the three fuses in the fan controller ( the plate thing is a 50 amp fuse). Then check the volts in and out on the rad thermo-switch when you expect it to be running. The red wire is volts in and is battery 12 volts sourced so ignition switched on isn't needed. The outputs are 12 volts on the other two wires, stage one red/white and stage 2 red/black.

 

 

Am I correct in thinking the thermostat (housing) you are thinking of is located beneath the coilpack. would you replace all of this --its quite a large part with plenty of connectors on it.

 

Invariably if you take the thermastat housing apart, it breaks due to heat making it brittle. So it is a thermostat + housing + seal. Three sensors should be re-usable. Don't forget to slide the clip out before pulling out the sensors. They are just plugged into the holes.

 

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[STORM 2 0]

Cheers RW1, you are a STAR. I will do all of the above tomorrow and let you know how it goes

[STORM 2 0]

OK update:

 

The bottom radiator hose is cold and the top is hot - what's more the run on fan isn't working either now :( --I cant drive the car for more than 500 yds now :cry:

 

So do I replace the thermostat or the senders on the thermostat housing? Anyone got any part numbers handy??

cheers

[RW1 0]

The bottom radiator hose is cold and the top is hot

 

Symptoms of the thermostat is shut/stuck.

 

Housing 021 121 117A

Housing seal to engine 021 121 119A

Thermostat 075 121 113D

Thermostat seal N 901 368 02

 

It's assumed all bolts will be re-useable.

 

You should only need the last two parts but as previously above, the housing is brittle after 10 years and will almost certainly give you problems.

 

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[STORM 2 0]

The bottom radiator hose is cold and the top is hot

 

Symptoms of the thermostat is shut/stuck.

 

Housing 021 121 117A

Housing seal to engine 021 121 119A

Thermostat 075 121 113D

Thermostat seal N 901 368 02

 

It's assumed all bolts will be re-useable.

 

You should only need the last two parts but as previously above, the housing is brittle after 10 years and will almost certainly give you problems.

 

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Cheers for the quick reply - Only thing is I have taken out the whole thermostat housing and chucked the thermostat in a pan on the cooker. The thermostat was closed at room temp and then slowly opened as the water began to boil. It opened about 10mm and then closed over 30seconds once it was removed from the water. I'm not sure if this is a satisfactory performance by the thermostat but does this mean its not faulty? If not, what do I do next - I'm tempted to replace the yellow sender...I disconnected it and shorted across the terminals of the plug diagonally and the fan came on...does this mean the sender is faulty?

 

Is the radiator thermoswitch still a suspect?

 

I also checked the main loom going to the radiator motor - I couldnt find any extra fuses but the fuses inside the car are OK (the one for the fan and the one for the fan run-on)

 

Many thanks for your help mate - it is much appreciated

[RW1 0]

The thermostat looks as though it open OK ( abit bit short but it depends on exactly what temp it was so not worth persuing at this stage). So why the lower rad rubber pipe is cold on the bottom hose at fully warmed up engine temperatures??? Can only think that the radiator is blocked which I don't believe or the negine wasn't fully warm, ie. it had been running at least 15 minutes before you did the check.

 

The yellow temp switch is only the run on after ignition off, so if thats defo not working when you expect with a very hot engine it's suspect after your jumpr wire check.

 

But also, check the volts on the wires on the rad thermoswitch before changing it to be sure the two output wires have volts or not as above before replacing it.

 

No extra fuses in the car, it's fuse 19 on the rack of them on the bottom edge of the fuse panel.

 

Other 3 fuses I mentioned are in the little clear plastic cover bit on the fan controller by the header tank in the engine bay.

 

Is the pump pulley being turned by the serpentine belt on the right side of the engine???

 

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[STORM 2 0]

Right, Ive ordered a new thermostat, yellow 4 pin sender, and the radiator thermostat. Oh yeah, and 500 gallons of G12+ :roll: . Am gonna do it tonight and see they solve the problem -will keep you posted, Cheers

[STORM 2 0]

Well, Ive replaced the thermostat (and housing) as well as the yellow sender switch, as well as the radiator thermoswitch and refilled the system (2nd time in 3 days), checked all the fuses AND STILL the temp gauge shoots up to 120 as soon as I start the car with the warning light flashing.

Also replaced the oil temp sender (--- on MFA) but still no oil temp reading either. :mad: :mad:

Both hoses are now hot and the fan kicks in at 115 for about 30 seconds with the engine running then stops...WTF? And finally there's still no fan run on once the engine is awitched off..

 

Oh yeah - and I've just seen some mayonnaise on the oil filler cap for the first time ever but the dipstick is clean as a whistle

 

I think its time for me to declare....I really feel like giving up and buying a 'new' car....

[STORM 2 0]

anyone got any ideas?

[STORM 2 0]

Add insult to injury! I was walking past the car in the morning (stone cold freezing) and the fan came on off its own accord!!! Car hadnt been started and it was -1 degrees outside?

Oh yeah, the fan motor housing was hot

Whats happening?

[RW1 0]

Given, the thermostat "fixed" the cold pipe off the radiator, maybe this is more than one fault.

 

If the fan is running on it's own accord, then either the thermoswitches are "ON" or the fan controller is doing something.

 

Next time the fan is running.

 

Disconnect the radiator thermoswitch down below the battery if it still runs, then disconnect the yellow temp sensor/thermoswitch in the thermosat housing. If niether stops the fan, then that leaves the fan controller itself or you have an electrical wire fault somewhere.

 

The odd thing here is the high switch on temperature above at 115'C which suggests that's either the third stage fan speed switching ON because 1 & 2 have failed to come on or the second stage fan speed is on one end of the tolerance (high end) when it comes on.

 

The third stage thermoswitch (black) is also located in the thermostat housing.

 

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[STORM 2 0]

Thanks RW1, In summary, current position:

 

1. fan does not work at all whilst engine is running.

2. fan ONLY comes on once ignition is switched off

3. Once "after-running" then fan CANNOT be stopped by a) disconnecting the yellow thermostat switch or, b) by disconnecting the radiator fanswitch

In this situation only removing the 20 amp fuse in the fan controller module wil stop the fan.

 

Eventually,left alone, the fan WILL stop of its own accord but as soon as the ignition goes to ON-OFF it starts again.

 

Do you think I should try a new fan controller module? (£100)

[Kevin Bacon 5]

I've got a controller you can try mate. I replaced mine because speeds 1 and 2 weren't working, but turned out it wasn't that after all.

[STORM 2 0]

pm sent Kev, thanks

[STORM 2 0]

OK tried Kev's old controller module with limited success but I think one of the relays in the old controller was dodgy.

 

RW1, I tried briding the terminals on the radiator thermoswitch connector and the fan worked (red and black/red) - which stage speed is this?

When I bridged the (red and white/red) terminals - nothing happened. Does this mean stage 1 or 2 isnt working? Having replaced the thermoswitch itself - is this a faulty white/red wire? [i tried sticking a multmeter on the red/ white and got 0V. I got 12V when I tried the other- input but no output?] Thanks

[RW1 0]

“Bridged Red – Red/White” That’s the stage 1 fan.

 

“Bridge Red – Red/Black” That’s the stage 2 fan.

 

“Red/White got 0 volts” Would expect that.

 

“Fan controller involved in radiator thermo-switch?” Yes it is. Stage one is monitored by the fan controller while at the same time the thermo-switch directly switches ON the stage 1 fan. Stage 2 fan is switched by the fan controller only. Stage 3 is switched by the thermo-switch in the thermostat housing (2 pin black) via the fan controller.

 

First line out the thermo-switch connection to the radiator fan motor for the Red/White wire. Is it OK?

 

Then apply 12 volts across the Red/White and Brown wire connections at the radiator fan motor to see if stage 1 will work. Just a contact enough to quickly pulse the motor (due to the current drawn). Is it rotating?

 

These are the only two failure conditions left for the fan stage 1 to check after the wire bridging already done. Bridging the thermo-switch connector has bypassed any question that the radiator thermo-switch is at fault.

 

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[STORM 2 0]

 

First line out the thermo-switch connection to the radiator fan motor for the Red/White wire. Is it OK?.

 

This seems OK - but its a pretty thick loom, well covered, going to the fan controller and disappearing off towards the back -where else does it go? to the ECU?

 

Then apply 12 volts across the Red/White and Brown wire connections at the radiator fan motor to see if stage 1 will work. Just a contact enough to quickly pulse the motor (due to the current drawn). Is it rotating?

 

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Yes, this is working,

 

So does this mean there's a fault in the loom somewhere?

[RW1 0]

where else does it go? to the ECU?

No, ends up on the rad fan connector. Just line out the whole length and ignore the fan controller is sitting in the middle.

 

So does this mean there's a fault in the loom somewhere?

Looks like it could be. If it does line out between the thermo-switch connection and rad fan connection, split the fan controller and line out to each; from fan control connection to rad fan connector and rad thermo-switch connector. Also check all end fittings in plugs are free from corrosion and damage.

 

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[STORM 2 0]

Well, I changed the expansion tank - having already replaced the cap with little joy, and hey presto - water temps of 80-90 no matter how its driven. I am highly suspicious that this is just temporary though!! Many thanks to everyone, especially RW1 and Kev - I will let you know if things go peareshaped again (do I hear a groan?)

[mariovr6 0]

i had i similer problem , Changed every thing and once i changed the expantion cap it was ok, but stand outside the car and you feel loads of heat........ All gone down hill now runs at 110

[RW1 0]

No probs.

 

Hmmm. I thought this was an issue of fans not working?????? Your solution is mechanical not electrical.

 

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[STORM 2 0]

thats exactly what I thought - but the fans seem to be running at all stages now - the only thing I could think of was if the low pressure was affecting the radiator thermoswitch stopping it triggering.....