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[Andy A]

Just purchased an Omega 2.6 Estate 2002. Didn't know about the problem until it over heated coming back home from buying it. All three cooling fans are not running most of the time. When the engine reached just over 100degC the two front fans came on but only for about 5 seconds and then went off. The main radiator fan didn't come on at all.

I put the multi meter on all 6 pins in the fan test connector with the ignition off and on to double check for voltages before grounding any pins and my results are below.

Ignition off
FT1 12V
FT2 0V
FT3 0V
FT4 0V
FT5 0V
FT6 0V

Ignition on
FT1 12V
FT2 12V
FT3 12V
FT4 12V
FT5 12V
FT6 0V

It shows on the diagram for testing that only pin FT3 should be 12v with the ignition on.

Clearly the test results can't be right.

What would cause this?

Thanks

[05omegav6]

Could be a duff relay then... iirc the fan relays are the same as the horn relay (green one under steering column)...

Be worth swapping them around to rule them out... Easiest way is to remove the horn relay and substitute it with both fan relays in turn.

Horn on permanently or not at all will point to the dead one

[Andy A]

Al, If the horn relay is the green one under the steering column, are the two green relays under the bonnet the correct relays for the fans?

Thanks

[05omegav6]

Precisely

Pull the under bonnet ones separately so that you know which one is the dead one, if that turns out to be the case

[Andy A]

Swapped the relays over and the relays seem OK.

Al, I know it's a big ask but is it possible for you or anyone else who reads this to check the voltages on all 6 pins in the green fan test connection box under the bonnet with ignition off and on?

Thanks

[05omegav6]

Can do, but won't be until Tuesday

[Andy A]

That's fine Al, Tuesday no problem. I'm glad you are willing to do it.

Thanks 

Andy

[LC0112G]

Just purchased an Omega 2.6 Estate 2002. Didn't know about the problem until it over heated coming back home from buying it. All three cooling fans are not running most of the time. When the engine reached just over 100degC the two front fans came on but only for about 5 seconds and then went off. The main radiator fan didn't come on at all.

I put the multi meter on all 6 pins in the fan test connector with the ignition off and on to double check for voltages before grounding any pins and my results are below.

Ignition off
FT1 12V
FT2 0V
FT3 0V
FT4 0V
FT5 0V
FT6 0V

Ignition on
FT1 12V
FT2 12V
FT3 12V
FT4 12V
FT5 12V
FT6 0V

It shows on the diagram for testing that only pin FT3 should be 12v with the ignition on.

Clearly the test results can't be right.

What would cause this?

Thanks

What you are measuring is the voltage on the low side of various relay coils. The high side of the coil is connected to the battery via a switched ignition feed (the ignition switch). A voltmeter in volt mode takes bu99er all current, so what you measure on the low side of the coil is battery volts. The fan switch (when operating) shorts the low side of the relay coil to ground, which clicks the relay into operation and applies power to the rad fan.

If you're worried about shorting things out, then change the voltmeter to measure DC current - say 500mA - and connect it between FT4 and FT6. The voltmeter will show you how much current it takes to operate the relay - and the relay will click, and the fan should run.

Or just grow a backbone and with the ignition on short FT4 and FT6 using a screwdriver/pair of pliers :-)

If the fan still doesn't run by shorting FT4 and FT6, then either the fan, relay or fuse is FUBAR.

[Andy A]

All tested and fans are running. So defiantly a faulty switch.

Thanks Al and LC0112G for your all your help. 

[05omegav6]

Glad you've solved it

[Kevin Wood]

As an aside, I made up a cable with a test probe on one end, and crocodile clip on the other and a bulb in the middle for checking these. The bulb limits the current if you do accidentally short anything, and it also makes a good general purpose test lead.

[Andy A]

As an aside, I made up a cable with a test probe on one end, and crocodile clip on the other and a bulb in the middle for checking these. The bulb limits the current if you do accidentally short anything, and it also makes a good general purpose test lead.

I have some crock clips and an old set of meter probes here that will do. I'm sure I have a spare 12v bulb in the car to solder on.

Handy tool to have. Thanks Kevin. 

[Kevin Wood]

As an aside, I made up a cable with a test probe on one end, and crocodile clip on the other and a bulb in the middle for checking these. The bulb limits the current if you do accidentally short anything, and it also makes a good general purpose test lead.

I have some crock clips and an old set of meter probes here that will do. I'm sure I have a spare 12v bulb in the car to solder on.

Handy tool to have. Thanks Kevin. 

Exactly how mine came to be...