Cooling Fan Wiring

[eNigMar]

Hi,

I have a 2001 2.5L Diesel Bongo. The front cooling fans are on from turning the ignition on.

This is a full conversion and I think the wiring for the fans has been altered (This is my first Bongo so have nothing to compare it to).

There is a relay on the drivers side that has a hot wire from the rear of the drivers fuse holder. This connects to the power input of the relay. The earth from this relay goes to the sensor and then back out of the sensor to an earth point on the body. The other side of the relay is wired to the fan relays next to the radiator (earth and power).

This means that the sensor should be doing the switching via the earth from the relay to the earth on the body.

The problem is that the relay is powered immediately upon connection meaning that the sensor is permanently closed. Hence the fans coming on immediately.

I tested the old sensor and found 0.00 Ohms between the pins. I changed the sensor for a new one and for the first drive the fans didn't come on. Yay! However, the next drive they did. I tested the new sensor and that is now reading the same 0.00 Ohms resistance.

The only thing that I can think of is that the sensor requires 5V and feeding it 12V direct from the fuse box is causing the sensor to fail.

Can anybody confirm that the sensor should have 5V and that 12V might cause this problem, or am I barking up the wrong tree and 12V is fine?

What else could cause a new sensor to go closed circuit after a single drive.

I have no temperature problems and have travelled many miles without issue.

Cheers,

Nige

[eNigMar]

S'ok i fixed it.

The relay was wired incorrectly. I rewired and all is good again.

It was wired so that the switching provided by the sensor was bypassed causing it to run whenever the ignition was on.

Nige

[Bob]

Well done.

[cst_tsc]

Where is the relay?

[g8dhe]

The radiator fan relays are located underneath and in front of the starter battery, a block of 6 relays, exact positions of the relays depends on year and engine type.