610 cooling fans

Phil - do check your fan electrics - you can test them individually, but both should work at the same time.

Hi Martin,

Yes, this was a point I was going to make after I heard how you had got on. According to my reading of the manual, there are only three ways that the fans will operate:-
1. Both fans off
2. Both fans running at half speed when relay 337 is energised.
3. Both fans running at full speed when relays 336 & 335 operate.
As you noted before, those relay coils are wired in parallel and can only get energised together. I cannot see any configuration of the relays whereby one fan can come on by its self, so if that happens, I suspect there is a fault.
A quick test for the half speed running, is when the Turbo bearing coolant pump is running for the 12mins after engin stop, relay 337 is energised, and power is applied to the fans in series, and they will both be running at 1/2 speed.
Clearly when the engin is really hot relays 336 & 335 are energised via contact A-B in item 206 which is the rad thermo switch, and both fans will be running at full speed.
The coloured diag I posted previously shows slow speed fan series operation, and below there is another diag showing the full speed circuit with both fans running.

I'd be very interested in seeing a key for all the relays in that diagram

Relay 337. Fan unit 3rd speed relay
Relay 336. Fan unit 2nd speed relay
Relay 335. Fan unit 1st speed relay
Relay 57. Fan relay via C.A.U.
Relay 465. Turbo bearing coolant pump relay
Relay 236. Fuel pump relay
Relay 474. A/C compressor control relay

Hope this is what you want

John

What's is CAU?!

Okay, I still can't see how the rad fans are meant to be powered relating to the turbo cooling pump. It wouldn't make sense to as the turbo cooling pump circulates from the header bottle and back round, but goes through the little heat echanger in the air flow of the deck lid fan - I bet this keeps the water to the turbo cooler than it would be sucking all the way from the rad (on quite a low o/p pump)

The diagram also shows the compressor relay being in series with the "slow speed" (series) fan relay - this is either very poor engineering, or wrong.

[mettersl]

Central accessories unit- the big box under the passengers feet, if you pull back the carpet you'll find it and a relay or two as well.
Often the source of electrical gremlins as its location can allow it to get damp, especially if you have rusty wheel arches or a blocked A/C drain.
Happy hunting.

The diagram also shows the compressor relay being in series with the "slow speed" (series) fan relay - this is either very poor engineering, or wrong.

Nope...not quite right, I`m afraid. Without doing another coloured diagram (running out of felt pens ) If you refer to the previous (series operation) diag, if you follow the earth up from the bottom RH corner, it goes to pin 92/96 of rad thermo sw, from pin C it goes up to B5 of connector R164, through the conn` to relay 337 coil, pin 2, thus supplying the earth fot that relay. If you go back to B5, and follow the wire down to blocking diode 322, it then goes to Pin 2 of the Compressor relay. What is not shown, of course, is the 12+ on pin 1. Now the diode is effectively an electrical "one way value", and in this case will not allow + volts to go up to B5, but will allow the neg current of the relay, to flow back to earth via B5 and rad thermo sw. 248. To summerise, even though it looks like the coils are in series, because of the blocking diode, electrically, they are not
Found out a bit more so I`m editing this.
Relay 465 is the one that the CAU grounds, via 6A, for 12mins on switch off, to run the bearing cooling pump. The relay also supplys 12v to relay 57`s coil in readyness. If the rad temp is equal or greater than 96`, as the CAU has grounded the coil of relay 57 already, it will be energised, putting 12v on relay 337`s coil, the rad sw will grounds the coil, which puts the fans in series, at 1/2 speed until either the 12mins are up, or temp drops below 96`. a bit complicated...but thats it in a nut shell

John