Relay issue on Radiator Fan High Speed.

[nrgsmith]

1990 1.6TD

I have been trying to work out why the Van is getting hot on long steep hills.
I cannot get my Radiator fan to work on High speed - it works fine on low speed.

I checked relay behind fuse box and changed relay. Everything seems to be connected correctly. 50 amp fuse is good.
I measured 12 volts across 50 amp fuse but when relay is triggered this 12 volts disappears. Bypassed relay - 12 volt to Fan but again when the connection is made the 12volts disappear.

Does anyone have an idea why the 12volts would stop when relay is triggered? Would it do this if there is a short or could there be another relay?

I checked wiring re Haynes manual.
Nick

[marlinowner]

Not sure what you mean by 12V across fuse - if there is 12V between each end of fuse, then the fuse must be blown or not making good contact. Or do you mean there is 12V at each end of fuse compared to ground?

[nrgsmith]

Sorry to be unclear.

The fuse is a 50Amp strip 12v + either end and 12v + going into relay. The fuse is not blowing. When the relay is triggered the 12v+ disappears!

[bigherb]

The power feed to the relay has a poor connection in the wiring, possibly in the junction box in the engine compartment.

[nrgsmith]

I'll check the connection in the engine junction box tomorrow. Thanks.

[nrgsmith]

Checked the Junction box today - cleaned up all the power feeds - cable going to high speed fan relay (red/white on my van not red as in Haynes) is not carrying power. Junction box connection is good and relay connection is good but no connection between, so the cable could be burnt out someplace unless it has another connection link broken that i have not found.
Next job is to run a new power feed from the engine bay and see if that will make it work.

[bigherb]

There is an single inline connector in the cable behind the dash.

[nrgsmith]

Thanks bigherb. There was one inline connection behind the fuse box coming from the cable duct from under the vehicle which then attaches to the relay. I checked that and it was good so looks like the cable has burn out. When I checked the relay to begin with the 50amp strip fuse had blown - It looked like the relay for the tow bar warning had come loose from its mounting and shorted against the fan relay.

[nrgsmith]

Update. Fan in high speed now working.

The original 12v+ must have burnt out somewhere along its route. I have run a new 70amp 12v+ cable from engine fuse box under van to the 50amp blade fuse behind front fuse box and now both radiator fan speeds are working.

[CovKid]

The fan, and notoriously the blower, can draw a great deal of amps as they age, causing heated wires and blown fuses. Unfortunately owners have a tendency to increase fuse ratings which puts further strain on wiring resulting in burnouts. 50amp fuse is certainly a big one on a 12v system. You have to be mindful that you're not just trying to fix the symptoms rather than the cause.

[nrgsmith]

I will be keeping my eye on it. The 50amp blade fuse is the recommended fuse for the relay for high speed fan.

[The Bishop]

Does anyone know what relay I need for the Radiator fan?

my high speed wasn't working and have traced this back to the fact that the relay is missing!!!!

[The Bishop]

And... why is a relay being used there?

It has the feed from the switch, and earth wire and the supply to the fan. What is happening in the relay? why cant I just connect the feed and the supply?

[bigherb]

It needs a relay for when it is on high speed it consumes more current than the switch is able to pass without burning out.
Which relay depends on which fan and relay you have. 300 watt with relay in the fuse box or 500w with the relay on the A pillar.

[The Bishop]

Many thanks.

I have the 300w with relay in the glove box.