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[Marks DTM Calib]

So ,if you know which relays do the back rad fan , bypass one at a time and see if your fan spins up  ,assume you have now tried the fan directly connected to a battery or power probe  refitted fan 
video here clicky for cars with air con but your's won't be all that different ,just no front fan and 2 relays not 3

I just pop the lids off so I can:

1) Observe if the contacts are making when activated
2) You can then manually press the relay contacts together to see the fan (or other ancillary) operate

[terry paget]

Tantalising suggestion - but how do I pop the lids off?

[Doctor Gollum]

Have a good look at a spare relay

[terry paget]

Swapped relays K12 and K13 (Hella made in USA) for K12 and 13 from 04 car (made in Spain). Idled engine for 30 minutes, fan never turned; disappointing. Plugged in diagnostic, revved engine to raise coolant temperature, at 102 degrees the fan engaged. Phew!

So it looks like it was a failed relay.

[Doctor Gollum]

Now sort the top end rattle before it eventually kills another car

[dave the builder]

I would just pull the relays ,test them on the bench, then check you have 12v + at the   live terminal of the relay socket,then jump the switched and live terminals and see if fan spins up 
(because you can do that test without the engine being hot and the ecu calling for the fans to be on)

removing the covers may be possible on newer relays , but you run the risk of the covers popping off every time you want to pull the relay 

also have you pulled the fuses and checked they are sound with a continuity tester / multi meter ,or are you just looking ,thinking they are ok 

Swapped relays K12 and K13 (Hella made in USA) for K12 and 13 from 04 car (made in Spain). Idled engine for 30 minutes, fan never turned; disappointing. Plugged in diagnostic, revved engine to raise coolant temperature, at 102 degrees the fan engaged. Phew!

So it looks like it was a failed relay.

ok, getting somewhere now

[terry paget]

I would just pull the relays ,test them on the bench, then check you have 12v + at the   live terminal of the relay socket,then jump the switched and live terminals and see if fan spins up 
(because you can do that test without the engine being hot and the ecu calling for the fans to be on)

removing the covers may be possible on newer relays , but you run the risk of the covers popping off every time you want to pull the relay 

also have you pulled the fuses and checked they are sound with a continuity tester / multi meter ,or are you just looking ,thinking they are ok 

Swapped relays K12 and K13 (Hella made in USA) for K12 and 13 from 04 car (made in Spain). Idled engine for 30 minutes, fan never turned; disappointing. Plugged in diagnostic, revved engine to raise coolant temperature, at 102 degrees the fan engaged. Phew!

So it looks like it was a failed relay.

ok, getting somewhere now

I checked the fuse for continuity, it was OK.
I found popping the relay cover tricky. I have removed one, cracking it in the process. As you say, this could make removing this relay again challenging.
If the fan fails again, I could pop this relay in and press the points closed, then the fan should turn. Or, as you suggest, I could simply remove a relay and put power on the output terminal with a simple link from 12v+ to output terminal, i.e. terminals 85 to 87.
I presume the relay that failed was the low temperature low speed one, if so goodness knows at what temperature the high temp full speed one kicks in.

[terry paget]

Now sort the top end rattle before it eventually kills another car

Next job, Doc, but I shall wait until sister returns my Omega.

[Nick W]

I presume the relay that failed was the low temperature low speed one, if so goodness knows at what temperature the high temp full speed one kicks in.

Probably says that on the sensor....


I wouldn't bother with dismantling relays, but keep a couple of spares. You've broken a number of cars Terry, emptying one of the relay boxes would have been a good idea.

[Doctor Gollum]

Now sort the top end rattle before it eventually kills another car

Next job, Doc, but I shall wait until sister returns my Omega.

Why wait? Removing those gauze filters takes ten minutes including a making a cup of tea

[Raeturbo]

Agree with getting rid of the filters, but it was probably noisy due to the excessive heat.

[Doctor Gollum]

Blocked gauzes won't help any. 

[terry paget]

Hi Doc,
just checking - are these shells the gauzes to remove?

[Doctor Gollum]

Them's the ones 

[terry paget]

Is it missing an O ring? There is one O ring, just behind the third groove, but no bigger O ring in the groove by the bolt bracket.