'98 Patrol GUII, ST,4500 - wiring diagram

[lloyro]

Hi, its Lloyro here; I have a problem with my Radiator fans 1 & 2 not turning on when engine starts to overheat. Presumably, the temp. sensor within the fan motor is open circuit. Has anyone had this experience before. All fuses and relays check out ok.
If anyone has a wiring diagram of this vehicle I would be appreciative of a copy.
Thanks, Lloyro

[stock patrol]

Hi, its Lloyro here; I have a problem with my Radiator fans 1 & 2 not turning on when engine starts to overheat. Presumably, the temp. sensor within the fan motor is open circuit. Has anyone had this experience before. All fuses and relays check out ok.
If anyone has a wiring diagram of this vehicle I would be appreciative of a copy.
Thanks, Lloyro

Can't help with a wiring diagram but my guess is the temp sender/sensor for the fan if the fuse is ok.

[lloyro]

Thanks for the back-up, I have found there is either a temp. sensor or an o/load cut-out within the rad. 1 fan motor. I would have thought the sensor would be operating with a rise in water temp. hence the need to have a wiring diagram to determine exactly what does happen. Lloyro

[Yendor]

Do the radiator fans come on when the air conditioning is turned on?

Have you checked for power and earth at the fan motors?

Did you check fuse number 6 in the fuse box inside the vehicle as well as the fuses in the fuse box under the bonnet?

[lloyro]

Thanks Yendor, have checked fuses inside vehicle and fuses and relays under the bonnet and are ok. I'll have to wait till engine is hot with A/c on to see if fans work then. On cold start up the fans do not run with A/c on. Have applied power to both motors manually and they both work ok. Lloyro

[Yendor]

One fan should come on as soon as the A/C is turned on, regardless of engine temp.

[lloyro]

Thanks Yendor - I didn't know that should happen and will check if one fan starts when air conditioner turns on. An electrical wiring diagram would be nice.

[YNOT]

18 more posts and you'll have access to the manuals on here, they have wiring diagrams in them.

Tony

[Yendor]

Fan one should come on when you hear the A/C compressor click in.

I would start checking at fan relay one, remove the relay and with the ignition on, you should have power at two terminals in the relay base.

If this is ok and fan relay one is ok, I would then check the air conditioning relay (I think it's brown in colour), this is a dual contact relay. One set of contacts supplies power to the A/C compressor the other set of contacts supplies an earth to fan relay one (switching it on).

You might have a problem with the contacts in this relay.

The fans can also be switched on by the ECU if the engine temperature gets to hot.

I'm not sure if the ECU can just switch fan one on by itself but it can bring both fans on.

[lloyro]

Hi Yendor, thanks for coming back; I have checked the system as per your suggestions and am happy to say the fans are now working ok. It is pretty obvious there must have been a bad contact somewhere (may be in the plugs at the fan motors). I'll have to keep a close watch on this.
The Rad fan 1 comes on immediately the A/c is turned on.
Having solved this problem with the fans I am still faced with engine overheating - I have a new thermostat coming and will fit today.
Lloyro

[Yendor]

Hi Lloyro,

It can be a real pain when you are chasing electrical problems and it starts working again.

Yes I would say you have a bad connections somewhere and going by what you have told me I suspect the problem to be with the A/C relay.

If it starts playing up again try tapping the top of the relay (engine running and A/C on) if the fan suddenly starts then this is your problem.

Good luck with the overheating problem.

Cheers Rodney

[lloyro]

I have now fitted the new thermostat and am happy to say the cooling system and the Rad1 & 2 fans are working ok. The best test will be when I go home (approx 1500km) towing the caravan going thru flat and hilly country. Thank you to all for your assistance and feedback to resolve this issue