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How to test a radiator thermostat????
FFTS - 17/3/10 at 05:04 PM

The radiator fan doesn't seem to be kicking in or maybe its just not getting hot enough to need to.

Don't know if I can trust my temp gauge. I have tried shorting the fan and it works ok so either the switch isn't working or its not getting hot enough to need to.

Any simple test I can do to check the thermostat switch? Its a big bolt in job to the top of the radiator with 2 spade connectors on it.

bmseven - 17/3/10 at 05:08 PM

Put it in a saucepan of boiling water

FFTS - 17/3/10 at 05:10 PM

quote:
Originally posted by bmseven
Put it in a saucepan of boiling water


And how do I tell if its switching? Do I take the pan of water to the car and drop the thermo into it while still wired to the fan?

blakep82 - 17/3/10 at 05:12 PM

is it a fan switch rather than a thermostat?

the thermostat just opens to allow water to move when it gets hot, so you can see it opens.

Breaker - 17/3/10 at 05:13 PM

Remove the thermostat from the radiator and put it (and a thermometer) in some water. Connect a voltage/resistance meter on the contacts and slowly start boiling the water and look at what temperature the resistance drops to around 0 Ohms. Let the water cool and look at what temperature the resistance rises again. This way you will find the switching temperatures of your thermostat.

FFTS - 17/3/10 at 05:16 PM

quote:
Originally posted by blakep82
is it a fan switch rather than a thermostat?

the thermostat just opens to allow water to move when it gets hot, so you can see it opens.


I I'm no wrong its a thermostatic switch. Theres no manual switch for the fan. Just 2 wires come from the fan up to the top of the rad where the thingy is screwed in. If I'm not mistaken I think its a thermostatic switch, i.e when it gets to a certain temperature it closes the switch turning the fan on and then when it cools off it should go.

FFTS - 17/3/10 at 05:17 PM

quote:
Originally posted by Breaker
Remove the thermostat from the radiator and put it (and a thermometer) in some water. Connect a voltage/resistance meter on the contacts and slowly start boiling the water and look at what temperature the resistance drops to around 0 Ohms. Let the water cool and look at what temperature the resistance rises again. This way you will find the switching temperatures of your thermostat.


Nice one!! Thank you

Breaker - 17/3/10 at 05:18 PM

quote:
Originally posted by Breaker
Remove the thermostat from the radiator and put it (and a thermometer) in some water. Connect a voltage/resistance meter on the contacts and slowly start boiling the water and look at what temperature the resistance drops to around 0 Ohms. Let the water cool and look at what temperature the resistance rises again. This way you will find the switching temperatures of your thermostat.


Oh, if you don't have a resistance meter; take a car battery and a car light bulb and put it in series with the thermostatic switch. If the light goes on.....you'll get the point

Bluemoon - 17/3/10 at 05:22 PM

quote:
Originally posted by FFTS
quote:
Originally posted by Breaker
Remove the thermostat from the radiator and put it (and a thermometer) in some water. Connect a voltage/resistance meter on the contacts and slowly start boiling the water and look at what temperature the resistance drops to around 0 Ohms. Let the water cool and look at what temperature the resistance rises again. This way you will find the switching temperatures of your thermostat.


Nice one!! Thank you


If it switches at <100C ! I think some don't??

turbodisplay - 17/3/10 at 06:05 PM

Just replace it. I had a faulty fan switch take the engine out!

Darren

dhutch - 17/3/10 at 06:17 PM

quote:
If it switches at <100C ! I think some don't??

If it switches at much over 100c it is potentially not much use to man or beast as a fan switch in a water based system. Particularly a fairly small one with a somewhat optimistic radiator is is typically the case with a seven type.
- I dont know many other places that would be using a 1.1 polo rad for a race tuned 2.0 engine for instance!

CDS offer the following:
107º/97ºC M14
100º/95ºC M14
97º/85ºC M14
95º/86ºC M22
88º/79ºC M22
87ºC/82ºC M14

You might be able to get the 107c one to open with some salt in the water, or by holding it against the bottom of the pan after its managed not to switch in a rolling boil. However, as said, i think i would be looking for something more like a 95º/86ºC if mating with a 80c stat.


Daniel

britishtrident - 17/3/10 at 07:28 PM

I find my infrared non-contact thermometer is great for this kind stuff --- Mapin have them on offer for the next week or so £25