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Rad thermo switch
LBMEFM - 21/6/08 at 09:39 PM

On fitting may fan today I thought I should check my fan switch (Vauxhall Caviler switch on MK rad) There are only two terminals, I connected them to check the resistance which when cold was 1 when I placed the end in boiling water for several minutes the reading did not change, I thought the switch would close to allow current to the fan. Does this mean the switch is faulty?

mad-butcher - 22/6/08 at 06:31 AM

I use a thermometer and the continuity setting on a multi meter when the buzzer sounds the circuits complete and you can check at what temp the circuits made
Tony

LBMEFM - 22/6/08 at 06:37 AM

That's what I did and even at boiling point the circuit did not close. So I assume that the switch is no good.

mad-butcher - 22/6/08 at 07:44 AM

Sorry missunderstood your original posting on my multi meter I can't check resistance and continuity at the same time, Personal opinion your better off fitting a new one I also have a light on the dash so I can see when the fan is running
tony

LBMEFM - 22/6/08 at 09:17 AM

Good idea with the light Tony, thanks for that, Cheers Barry

02GF74 - 22/6/08 at 09:21 AM

quote:
Originally posted by mad-butcher
Sorry missunderstood your original posting on my multi meter I can't check resistance and continuity at the same time,


oh yes you can!! continuity is when resistance is low, typially 1 ohm or less.


.... but back to the problem.

there are 3 tereminals - did you check resistance between the terminals and each terminal and the body?

there are some thermo switches that operate at two tempearatures.

also what is the value of resistance? if in region of 300 - 1 K ohm then that would probalby be a temperature sender .. and resistance would change when you heat up the water.

if in doubt, replpace - they are less than a tenner anyway.

do search for X-eng and look for the thermo - switch data - this shows data for a whole range of switches (note the thread/fitting my be different to yours)

BenB - 22/6/08 at 11:15 AM

Sounds like its knackered.....
It should go to zero ohms well before boiling....

Steve @ sVc - 24/6/08 at 01:28 PM

Warning light for cooling fan.

We have had a number of confused customers as often the fan warning light comes on when the fan is switched off.

When driving, the air causes the fan to turn - this turns the fan motor into a dynamo and reverse feeds power into the warning light. A diode solve the problem.

Regards
Steve @ sVc