Radiator fan always running??

[martin1810]

I mean relays on this relay plate. Not the 13 position one.

https://www.vwaudiforum.co.uk/forum/a...pictureid=2514

[Chipped2]

I mean relays on this relay plate. Not the 13 position one.

https://www.vwaudiforum.co.uk/forum/a...pictureid=2514

Hi Martin,

The relays on this lowest 'Additional Relay Carrier Relays I - IV' are as follows;

I..... Relay 53
II.... Relay 370
III....Relay none
IV....Relay 202
V & VI....Relay 192


Above this is the 'Additional Relay Carrier 1 - 13' which has the following;

1......none
2......none
3......relay 267
4......none
5......none
6......none
7......none (but has an unused 7-pin socket)
8-9...relay 452
10....relay 167
11....none
12....none
13....none

I then have a additional relay carrier above this which has three sockets numbered in reverse order as follows;

3.....relay 370
2.....none
1.....relay 373

Does this make sense as you do not mention this relay carrier?

Many thanks, Paul

[martin1810]

To save all this mucking about with relay locations. Find the fan switch in the radiator. Should be a 4 pin connector. Turn ignition on "cold" If fan starts constantly running, pull the connector off. If fan goes off, temp switch is faulty. If fan stays on , relay is faulty. Then we look for relay again.

[Chipped2]

Have ordered a new thermoswitch from VW. May as well replace it when the undertray is off.

[Peter D]

But you do not know if it is faulty. Add to that you are going to loose your coolant. Regards Peter

[Chipped2]

Hi Peter, I do agree with your comments but I have a 75 mile return journey to the nearest dealer in Aberystwyth so thought it best to get a new switch while there later this week. However as you suggest I will test the existing one before replacing. Think they are about £17. I'm hoping that I can minimise coolant loss with a quick swap-out !! Sounds OK in theory but I will have a container or two available as it was new G12 a year ago.

[Chipped2]

To save all this mucking about with relay locations. Find the fan switch in the radiator. Should be a 4 pin connector. Turn ignition on "cold" If fan starts constantly running, pull the connector off. If fan goes off, temp switch is faulty. If fan stays on , relay is faulty. Then we look for relay again.

Hi Martin,

OK, have turned on ignition with engine COLD, left on for a couple of minutes........radiator fan has NOT come on. ( Only interior fan has come on at a low speed, external temp 12 C climatronic set at 18 C. )

Am replacing Thermoswitch with new unit. Can you tell me from my previous posts which relay is likely to be controlling the radiator fan?

Thanks.

[martin1810]

I can't tell from your info but the relays are usually 370 and 373. So if the fan won't go off you could simply pull a relay out one at a time. If fan goes off you have found a relay. Depending on how your car was wired up there may be up to 3 relays for the fans, so you may identify 2 relays that stop the fan. Then it will be a case of working out which one is faulty. Hopefully it's the temp switch. Good luck.

[Chipped2]

I can't tell from your info but the relays are usually 370 and 373. So if the fan won't go off you could simply pull a relay out one at a time. If fan goes off you have found a relay. Depending on how your car was wired up there may be up to 3 relays for the fans, so you may identify 2 relays that stop the fan. Then it will be a case of working out which one is faulty. Hopefully it's the temp switch. Good luck.

New temp switch in and as expected from the test tried the fan still runs. So will attack the relays as suggested. Many thanks.

[Chipped2]

Tests on the relays with engine and radiator fan running.

When Relay 370 in position II is removed it stops the fan.

The Relay 370 and the Relay 373 on the topmost relay carrier that is rerverse numbered 3, 2, 1, have no effect on the running of the fan when they are unplugged.

I have also swapped the two 370 relays and found that there is no difference in the running of the fan. When all three relays are oppened up there is no signs of burnt or welded together contacts.

Can I safely unplug any other relays to see if they stop the radiator fan when running?

Can you suggest any other action I can take ( other than leave well alone and to just accept that the fan always runs !!) to resolve the problem?

Thanks for all help. I really do appreciate it.