Temp Gauge Not Reading Correctly

[Guest Jonnyround2003]

I have smiths gauges off a ford Sierra temp sender the Guage reads that it's really hot when it's not any ideas guys

[Longboarder]

Senders have to be matched to the gauge. Any old sender just won't do. Or then again it might be broken.

 

Nigel

[IanS]

If you do not have a voltage regulator then even the correct sender & guage combination will read hot.

[Guest Jonnyround2003]

I have tried it with a voltage regator and the Guage won't work at all cod it be faulty or do smiths garages only work on 12v

[nigelt]

Hi Jonny,

 

There are two types of Smiths gauges, moving coil and moving magnet. Or put another way, simple and not so simple. The simple ones just need a regulated voltage on the B terminal and then the other terminal goes to the sender. The not so simple ones need a regulated voltage on the B terminal and the body of the gauge wired to earth. (This biases the meter and stops the needle flopping about). The other terminal then goes to the sender. If your gauge is of this type and you don't connect the body to earth then you will get wild readings. However, as mentioned already if the sender and gauge don't match you won't very good readings.

 

Nige

[Guest Jonnyround2003]

Which sensor is the sender is it the one on the thermostat housing or the one that brings the fan on ?

[Guest Barry Knowles]

its behind the dissy cap..if its a pinto

[Guest Jonnyround2003]

Dohc engine

[Guest 2b cruising]

Switch for fan is on thermo housing.

Sensor for management is the three wire plug just behind the fan switch. If you have injection.

Sensor for gauge is just behind that on the drivers right hand side of engine.

I have been searching myself at the wiering diagrams but cannot find which is the relay for the engine fan.

Fords name all the fuses but not the bloody relays. I've been pulling my hair out looking for it.

Anyone help?

[Peter Bell]

It's shown in the Haynes book wiring diagram but just listed as item 38 no ford ref though. Should be in the later car handbook?

[Guest 2b cruising]

Found that, however, lift lid on fuse box and relays are marked a b c and onwards.

No reference picture or diagram pointing out which is what.

[Longboarder]

You have a cooling fan switch (heat operated). It has a black wire supplying it and two black reds coming from it which go to the twin fans it used to have. Ignition is activates the radfan relay and that black supply to the rad fan switch becomes live. So connect a voltmeter/bulb/whatever to that black wire and complete a circuit to earth. Now switch on ignition. Voltmeter registers/bulb lights/whatever. Start pulling relays and replacing them till you find one(maybe more) that cut the power to the black wire. If your are lucky its just the one relay and thats the fan relay.

 

Nigel

[Guest 2b cruising]

Hi Nige and thanks for info.

On mine there are supposed to be two relays, one for low speed and the other for high speed.

There is then a 5 terminal switch on the thermo housing to do the two jobs.

Must have two bye metal strips of differing values in the switch or similar.

I fiddled with it this morning and found that crossing any of the 5 terminals in the plug, except for the two together, the fan started working.

Did nothing else to it except put the plug back on.

My gauge is now more irratic than it was before, could be air in system by switch. However the fan is now working.

I must have unstuck something, maybe a set of points in a relay.

I read a little more into the subject today and found the cosworth switch, same as mine, was a week link with the fans being in use for long periods. Burton now do a more reliable switch especially for hard working engines.

As mine had a bad overheating problem last year I think this might have been my problem.

The switch itself was ok on testing last year but could easily have been on its last legs.

I am off on a run out tomorrow so will see how everything goes.

Edited August 21, 2015 by 2b cruising