Cooling fans unusual problem

[B_land]

I seem to have an unusual problem which must have occurred since the last MOT (September 2013) where the fans were reported to be working. I have used the Elan in the dry ever since, not many miles either and have not had to use the fans during this time, the Elan is on sorn over the winter but I've started to run it every 4 weeks. This week I ran it to 3/4 to check the fans but instead the cooling pump started without the fans (not normal) the pump continued to run after switching off (normal).
I've followed the checks in Wikii and the switch, fuses, relay and earth are fine, however the cooling pump runs when the switch test is performed with ignition on or off, the fans do not run.
The only electrical change was a new alarm fitted by a specialist last August but I cannot see how that could affect the cooling system.
I'd appreciate any thoughts that you guys may have

Cheers
B_land

[GeoffSmith]

Most likely the cooling fan relay (#C under binnacle) or (less likely) it's wiring or supply:

http://wikilec.9600.org/images/e/e0/MJ2 ... g_Fans.gif

http://wikilec.9600.org/images/9/9c/MJ2 ... Relays.gif

Probably the easiest test is to swap it with the adjacent blower fan fast (#D) relay.

[B_land]

Thanks Geoff,
Yes to check the relay I've changed it with more than 1 from the box but without success, I'm thinking that it's supply or wiring now

[Ade]

Hi,

have you checked the earth, the one just above the radiator in the centre, best viewed from beneath. If it works loose the fans wil not work.

Ade.

[B_land]

Thanks Ade
I've checked the earth on radiator frame and it's clean and tests okay. I will be speaking to the alarm specialist tomorrow because after successful component testing today it can only be a problem with the ignition wiring which the alarm specialist altered, too much of a coincidence

[GeoffSmith]

Because the recirculating pump is still running, it means that the relay is not switching, rather than anything to do with the fan wiring.

[B_land]

Geoff,
I've swapped the relays around without success and have concluded (unqualified) that there is no supply to the relay to switch it via the ignition switch

[GeoffSmith]

Sounds like the most plausible explanation given your re-wiring work.

[B_land]

Well the alarm installer has said he has not touched the fans, so I have done further testing and the fans run with direct supply from the battery. I've tested the earth, relays and fuses and these are fine however there is a link wire shown on the circuit diagram from the cooling fan relay to the diode and when tested there is an open circuit which I believe is caused by a faulty diode. The problem is that I have no clue where the link runs to and where to locate the diode in the circuit.
is it behind dashboard/relay box. :bang-head
Appreciate any advise.

Thanks

[B_land]

Update
Took the car for MOT and service today the garage hooked up the fans to run continually and the car went through MoT with no advisories. They tested the fan circuit and found the diode to be at fault but couldn't find it so have spiced in a new diode and now fans are working as they should.

Thanks