temp sender identification W124

[marshie001]

can someone please tell me what the sensors are?
ive figured out that the top one with the green wire is the temperature gauge

 

[grober]

Educated guess only from wiring diagram for 2litre 190e.
1 single green wire -engine temperature gauge
2 twin wires -thermo time/temperature switch for injection system
3 single wire lower down- thermo switch for electromagnetic fan-engine ?? Funny I sort of remember 1 and 3 being the other way round in real life. If you earth the fan lead momentarily the electromagnetic fan should come on. Watch you dont get hit with the fan!!!!!!

 

[turnipsock]

My guess:

The two wire thing is a switch, the one wire things are sensors. One will go to the gauge on the dash, pull off a wire to see which one screws up the gauge.

The fan switch should have a black/red wire and a black/red/white wire. You need to join these together to get the fan to kick in.The Black/Red should be the feed and should have 12V when the engine is on.

When working correctly, the fan should switch on at 102C

 

[marshie001]

thanks, so if i earth the fan wire it should clunk the clutch with the ignition on??

what if it doesnt work?

 

[turnipsock]

thanks, so if i earth the fan wire it should clunk the clutch with the ignition on??

NO! it will blow the fuse (F7)

Check the voltage on that reddish/black wire, it should be 12V

 

[marshie001]

ive got no voltage on the red/black wire at all!!

i havent got a multimeter but i stuck a 12v light up tester on it and nothing happened!
but i also checked the temp gauge wire aswell and that also has no voltage running through it but the gauge does work....

 

[Myros]

i think

the temp sender will work on the resistance of the sensor, rather than huge voltages. As the temp changes, the resistance changes and the temp needle will move to reflect that. Probably millivolts rather than a dozen of them..... You might need a mulitimeter after all, only so you can check the resistance of the sender.

 

[marshie001]

so the hotter the car the more millivolts should show?

is there a way of testing the wiring then?

i know for a fact that the sensor is knackered as i switched wires from the temp gauge and it showed nothing!

so in theory if i swap wires again so the good sender is connected to the fan circuit and leave the car to idle for a bit it should kick the fan in?

 

[turnipsock]

There should be 12V on the red/black wire with the car running and the fan off. If the switch is shorting out, then fuse 7 will blow

Can you see what colour of wire is going to the fan? It might be easier to trace the wires back from the fan.

 

[turnipsock]

I had a quick check under the bonnent (before the midges got the better of me) tonight.

Marshie, your engine looks identical to my 230TE.

Where you have the green wire, I have a green/black wire. According to haynes, this is the one that goes to EZL control unit.

Where you have that red/black wire (circled), I have a green wire. According to haynes, it's a green wire that goes to the temp gauge.

I pulled the plug of the double wire thing and started the car. I checked the voltage on the conector and there was 12V on the contact marked '1'. I think you should try the same test as if you don't have 12V there the fan will never switch on.

That conector looks a bit different from mine as I have two things to squeeze in to release it.

 

[marshie001]

yeah i swapped the green wire over to the top sender because i knew that one worked and i wanted the gauge working, thats why i needed to know what the other black/red wire was from, thanks for your help turnipsock, i have a new sender on order to be collected in the morning so hopefully i can sort this out.

 

[marshie001]

right.....bought a new sender this morning and tested the voltage on all wires with engine running....i have 12 volts at each actual nut where it comes in contact with the head but not at the prong where the wires connect???? im starting to lose the will to live now, its doin my brain in....

 

[turnipsock]

How are you measuring the voltage?

 

[marshie001]

still with my trusty screwdriver....i went back and had another go and i had power at the two wired switch that i circled, but then it disappeared, i also have lost power to the gauge sender now aswell.....where are these things getting their power and where are they earthed?

 

[turnipsock]

still with my trusty screwdriver

I think that's the problem.

You need to get a meter or a bulb. Maplin's will probably have something like a car battery checker you could use.

The temp gauge is just a meter and the sensor is just a thing that varies resistance with temperature. 12V-gauge-sensor-ground. As the sensor resistance changes so the gauge changes.

If you take the wire of the temp sensor, you should see ground on the sensor and 12V on the wire (only with a meter).

 

[marshie001]

getting somewhere now, i have 12v at the red/black wire but only for a few seconds after engine started...ive come to the conclusion that i have a short somewhere or a dodgy earth,can anyone let me know where this loom gets its power or where its earthed? ive tried to trace it but its like looking for a needle in a haystack.....

as its only powered when the engines running does this mean that its probably coming from the alternator?
or have i been overdosing on stupid pills again?

forgot to mention....dont know if its relevent or not...my temp gauge sits at over 120 when engines first fired up

 

[Myros]

ouch

Marshie, the single wire from my temp gauge sender broke recently, and the gauge went from 80 to zero in the bat of an eye. We can therefore assume that the infinite resistance the breakage caused = no temp reading, and that the reading increases with resistance decrease as the sender hots up. In order for you to be getting 120 at start-up, the opposite must be true to some extent, so yes, i think you have a short in there somewhere. First wire to check is the temp guage sender wire, then the temp gauge sender, and then I have to give up as all this talk of electric fans makes me giddy.
If they pan out ok, I've no idea what the problem is. The joys of a slightly senior car.

 

[turnipsock]

The 12V should be on the Red/Black wire on the double connector when the engine is running. The wiring starts at fuse 7, then goes through the ignition switch then to pin 1 on the double connector circled in the picture.

On the temp gauge side, it does look like a dodgy connection somewhere. In fact the wiring looks a bit suspect in general, do you know if there has been a problem in the past?

 

[marshie001]

ive no idea, it does look a bit dodgy i agree, theres something not right somewhere, ive bent the arms on the fan today so the magnet is holding the fan on all the time....so at least i can drive the car now without the fear of overheating, i'll just bend them back in the winter!

the temperature gauge isnt working at all now, it moves up ever so slightly when ignition is switched on but thats it....i give up.