Fan relays - 3 boxes, anyone know what is what?

[rwb]

Righ then: teach me some electronics ;)

So, 1509 active runs the fan at high speed, and is independent of the states of the other two.
For low speed it's 1508 active and 1509 inactive, so the resistor reduces the fan speed.

I see that 1514 puts a second resistor in parallel with the first one, and thus halves the total resistance, so I understand that the speed increases to medium.
1514 is activated by the air con, therefore the statement: "if you turn on the air con then the fan will run" is false because the fan already has to be running at low speed for 1514 to have a supply.

The power is coming from the fuse box, right? So what's the link into the ECU for?

And what's the symbol for 'dead wasp'? It's missing from 1506A.
(I think it was in the grey one, but we think it's the black one that's duff. Physically, the resistors are upside down compared to the relays -- this sort of thing drives me potty.)

[steve_earwig]

I see that 1508 creates a parallel route from the fuse box but with a resistor on it. I don't understand why this would reduce the fan speed.

When the high speed relay isn't closed, this is the only way the fan gets power, via a resistor.

The power is coming from the fuse box, right? So what's the link into the ECU for?

Control and/or signalling (it raises faults) Later car's fans are run straight from the ecu with no pressostat.

1514 has no effect on high speed, but turns low into medium if the air con is on.

If you say so

Therefore the statement: "if you turn on the air con then the fan will run" is false.

Or will it run at low speed via the mid speed resistor and relay? Dunno, all I see is the wiring which doesn't tell me much about function.

[Sonia406]

Sorry Steve... It's nice to know someone pays attention to my blog...
Build code is 8773
Someone managed to not only break her index finger but damage the tendons in there, so have spent a couple hours in Minor Injuries and had an x-ray..

So, chances are its the resistors that are ka-put? Thanks for all the diagrams and information everyone, shall have another crack at it soon...
I just put all the seat belts on, torque wrench managed to slip off the bolt and whacked my poorly finger, there are no words but I have just done the 'OUCH that really hurt' dance again...........
It slows me, but won't stop me ha ha..........

[steve_earwig]

Ouch! Sorry to hear that

Yes, from what Puggy said, it's probably the resistor(s). You should really test it to make sure though. They're about 19 quid each, different values but one's black and one's grey...

[puggy]

very easy test , unscrew them and look at the coil , if rusted to fook
and break in the coil they are fubar

[Sonia406]

very easy test , unscrew them and look at the coil , if rusted to fook
and break in the coil they are fubar

Cheers everyone, Shall have a look on Monday, when the house is a little quieter........