can any one help with the correct operation of coolant fans ?ac on no fans come on only after 5 mins for a 7 second period fast 

suspect fan module any advice please 

Edited 20 November, 20187 yr by tadonbeer

First thing to check is fuse 8 in the battery-top fuseholder. It's a 30A blade fuse in a covered section to the right of the strip fuses as you look from in front of the car.

 

will do. can turn em on fast speed with snap on diag so work just not on slow speed . replaced pump as old one pulley broke 

Some cars (earlier ones?) have two-speed fans for both the main and the smaller fan, in others the main fan is two speed but the smaller one is single speed (coming on with low speed operation of the other one, and staying on when the main fan goes to high speed). If the fuse is OK, have a look if you can see how many wires go to the motor of the smaller fan. You may well find that the loom connector has three wires, but only two continue to the fan itself.

Failure of the low speed can be caused by an internal resistor inside the fan housing breaking. It's happened on the main fan of both of our cars, but in those the small fan is only single speed-two-wire, so that one kept going.

 

Fuse 8 runs both fans at the low speed, strip fuse 5 (on your car, I think) does high speed, so you'll find that one intact, I expect.

Edited 20 November, 20187 yr by Wino

checked fuse all intact not blown.maybe the fan module on nsf lower near rad maybe ?all wires in tact to it so maybe module fault

 

Could be, but I'd want to check out the fans first. If you unplug them from their loom connectors, then measure resistances of the fan motor between pins 2 and 3 of the motor side connectors, you should see a low resistance on both. Thinking about it, the fact that both fans come on at high speed periodically suggests that your smaller fan is a twin speed one.

 

yes looks like it is pretty much out of ideas 

 

Check the fans themselves before you spend out on a new module, it really is very common that the internal low speed resistors inside the fans fail. Can be fixed without replacing the fans if you're OK with wiring and a little DIY: https://www.briskoda.net/forums/topic/404143-radiator-fan-repair-courtesy-of-vortex-here-and-uk-mkiv-forum/

If you can get a cheap/free module to swap in and test, fair play though.

 

Edited 20 November, 20187 yr by Wino

ill do a resistance test on fans then first . what readings should i expect to see ?

 

You'll know if the resistors are blown 'cos you'll get a very high resistance, normal is probably just a few Ohms, single figures.

fans unplugged ohm meter set to 200 and i get 0.04 on both. no voltage at plug engine running   till high pressure reading off scale then 14.5 volts for 7 seconds 

now this is surly where i should get 12 volts to run fans slow so fan module got to be at fault

 

Yes, sounds like solid diagnosis, as long as your 0.04 readings were pin 2 to pin 3 not pin 1 to pin 3? Sounds almost too low to be via the resistor. 

The low speed volts should likewise appear between 2 and 3, high speed between 1 and 3. Can you confirm this is what you did?

Edited 20 November, 20187 yr by Wino

i need to revisit and retest just to make sure 

 

Here's the circuit, it may help you to visualise what goes on (J293 is the Fan Control Module, it also has connections from A/C panel, and an ignition and permanent live feeds on the smaller connector T6v which aren't shown on this page):

 

Edited 21 November, 20187 yr by Wino

many thanks will update later