Hi all,

I have a problem I can`t seem to get my head round, my rad fan is not kicking in (except once yesterday for a minute), I have replaced the fan switch on the rad but this has not fixed the problem but if I short the connector on the fan switch the fan operates.

I noticed the thermostat housing has a sensor on it does this have any control on the fan? and if it does can i bypass it to see if that is the cause?

what I have done:-

Replaced rad a few months ago as the old one sprung a leak.
Replaced switch on Rad
Bled coolant system and checked that I get a return flows to the header tank when the engine is revved slightly.

but the fan will not kick in, if I bypass the switch on the rad so the fan is on constantly i have no issues with overheating so the overheating is being caused by the fan not kicking in.

any suggestions?

Have you checked the relay in the box at the front of the battery?

I had a look at them one (the bigger one on the rights contacts were a bit dirty so I cleaned them up)

Which of the two relays is the one for the fan?

When the car overheats, have you felt the radiator, to see if that is getting overheated aswell. Because if it isn't, the fan wont turn on and could mean that you still have an airlock in the engine

Yes the rad is overheating also (the water is circulating in the system) just the fan won`t kick in

Update: now i`m even more puzzled

As I have the old switch I decided to test it with a multimeter and heatgun in the house and it appeared to work, so i then took it to the car and connected the connector to it and applied heat with the heatgun and hey presto the fan kicked in ran for 2 minutes then shut down again, so the electrical side appears to be fine.

I have checked the three bleed points and water comes from them all I have checked the return feed to the header tank and that has hot water returning through it.

I have even loosened the rad switch while it was hot and it leaked hot water from it so the switch is in contact with hot water (just to rule out a blockage preventing the hot water touching the switch)

A friend said maybe the water pump is not circulating the water but I can`t see that being the issue because the water in contact with the switch is hot so the switch should activate.

Any suggestions?

Had simlar problems with over heat. changed the stat and sender...and end of...went to scrappy for stat as very expensive for new as a sealed unit.
Even in traffic temp gauge now stays mid way.
Just a test... if you turn heaters on full does the temp gauge drop to mid??

Its possible for the relay sockets to corrode and wires to drop off. You can check by shorting across the contacts

Renegade_8 said:

Its possible for the relay sockets to corrode and wires to drop off. You can check by shorting across the contacts

Click to expand...

It can't be that because connecting the Old switch to the wiring and applying heat the fan works so obviously the electrical side is functioning.

are the heaters working?

bulldog5046 said:

are the heaters working?

Click to expand...

Hi Ry yes heater works fine, logically the fan should be working as heat applied to the sensor on the rad activates fan and hot water is in contact with the sensor in the rad.

I just can`t get my head around it.

My car doesnt have a rad switch, the ECU looks at the sensor on the thermostat and decides when to kick in the fan. It can be overidden by the a/c triple switch and/or put to high speed. What year car is it?