Thread: 300Tdi 1997 Disco thermostat housing

No they're not - they are the aircon switches - one to cut in the fans when the engine gets a bit too hot, the other cuts out the aircon similar temp. You'll know if you get them hooked up wrong because the aircon fans will always be on. The temp gauge is the single stud device on the side of the housing.

The switch sensor closest to the thermostat is for the fans. According to the specs, switch on at 100 C rising, switch off at 94 C falling.

The switch sensor closest to the radiator cuts out the aircon clutch engagement at a rather scary 115 C.

Thanks for the help, but do these two switches have a name. I cant find any thing that matches your function description in the Haynes circuit diagrams.
Maybe they are only fitted to certain models exported to high temp countries.

Being 2 wire I should have realised they were not a thermistor.

If possible, could you please send a link to the Australian 300Tdi circuit diagrams. I have Defender diagrams but no Discovery wiring diagrams.

I do have RAVE, but it is for my P38.
Anyway - many thanks

I have a suggestion for Haynes manuals, Paint it green and throw it in some tall grass, Regards Frank.

Why do you need the wiring schematics, you should be able to just plug the sockets to their respective terminals, I have a 93 Disco LR factory manual, I could possibly scan it and email it to you, but no guarantee that it will be the same as on a 97 Disco, PM me if you want me to send, Regards Frank.

Attached is a picture part numbers and function of the switches.

first of do somthing useful with the haynes, give it to a pulp mill so it can be reprinted as a newspaper or used as toilet paper. I've been known to stack them and drill them together and use them for wheel chocks and anyone who turns up at my place with a vehicle with a problem that they've tried to fix "according to haynes" gets the price jacked up.

with that step completed goto the dave can do IT banner and then purchase the Rave CD suitable for your vehicle.

there are 3 senders in the same area

a small single wire jobby which is the temperature sender

the two on the elbow. one kicks the fans on under all circumstances if the engine begins to over heat (even if the AC is off providing that all the fuses and electricals are functional) the other cuts the AC out completely.

to work out which is which just probe them with a meter, the one that is NC with the engine at room temp is the one for the AC cut out and the one that is NO is the one for the fan override.

to test them set up a good fan in front of the engine bay, open and leave open the bonnet remove the shroud, remove the fan VC wind the windows down and run the engine up at high idle with the AC on. the first thing you should notice is the fans coming on an staying on (you may need to pull the AC fan relay/fuse) then the temp gauge should swing off of the normal position to just under the hot/overheat point and then the AC pump should cut out. as soon as the AC pump cuts out from the overheat protection re-enable the AC fans, set low idle and turn on the fan in front of the engine bay. leave the AC off.

ON EDIT....

you NEED a good infrared thermometer to monitor the temps at the senders if it gets past 120deg C carry out the cool off procedures of going to low idle and getting the air flowing through the radiator, you should also have a hose ready to spray gently onto the radiator. (the normal temperature sender should move from the middle to hot at about 105-110 and then begin to climb rapidly into the red overheat mark)

DO NOT just shut it down the heat soak in the block will be enough to boil off the coolant in the engine and may be enough to either force the cooling system to vent out the cap or cause a hose/tank/radiator failure.

That is great info. I was looking at these exact switches yesterday and wondering why there are two. And now I know. The power of AULRO...