Temperature guage sensor
Discussion
Hello from a new owner of a 1985 350i. This forum has been great for information, thanks a lot, and I'm currently waiting delivery of the Heath Wedge book to help me find my way round my new toy. In the mean time, does anyone know where the temperature guage sensor is situated and where I can get a new one from ? Thanks again.
Hi there.
There are two brass & plastic jobbies just by the distributor in the inlet manifold.
One of them is the thermotime switch. This activates the extra air valve (it gives the engine a bit more air when its on cold start). I believe this is the frontmost of the 2.
Behind it is the coolant temperature sensor, which drives the gauge. Its basically a bit of electrical kit whose resistance goes DOWN as it gets hotter (Negative Temperature Coefficient, NTC). Thus, if you connect it in series with the gauge, as it gets hoter, its resistance goes down and more of the 12 volts is applied to the gauge, moving the needle further.
Ed.
There are two brass & plastic jobbies just by the distributor in the inlet manifold.
One of them is the thermotime switch. This activates the extra air valve (it gives the engine a bit more air when its on cold start). I believe this is the frontmost of the 2.
Behind it is the coolant temperature sensor, which drives the gauge. Its basically a bit of electrical kit whose resistance goes DOWN as it gets hotter (Negative Temperature Coefficient, NTC). Thus, if you connect it in series with the gauge, as it gets hoter, its resistance goes down and more of the 12 volts is applied to the gauge, moving the needle further.
Ed.
ed_crouch said:
There are two brass & plastic jobbies just by the distributor in the inlet manifold.
One of them is the thermotime switch. This activates the extra air valve (it gives the engine a bit more air when its on cold start).
Behind it is the coolant temperature sensor, which drives the gauge.
Ed.
One of them is the thermotime switch. This activates the extra air valve (it gives the engine a bit more air when its on cold start).
Behind it is the coolant temperature sensor, which drives the gauge.
Ed.
The thermotime switch controls the cold start injector depending upon the temperature of the coolant.
The adjacent temperature sensor advises the ECU of coolant temperature to vary the fuel/air mixture ratio during warm up.
The EAV allows more air to be drawn into the engine, bypassing the throttle disc, thus raising the idle speed to overcome increased engine friction loads when cold. It shuts completely when the engine is hot.
ed_crouch said:
Oops, I stand corrected there. So theres THREE (?!?) temperature sensors...?
Ed.
Ed.
Yes. Front left: thermotime switch. Behind that: coolant temp sensor FOR THE ECU so it knows how hot the engine is. Both screwed vertically downward into inlet manifold.
Front RIGHT, screwed horizontally into the front wall of the inlet manifold, is the gauge sender.
The Guinnster said:
If this was top trumps it would be great, " 8 cylinders and 5 temperature sensors!" I'm getting confused now. I can't even go look as its pouring down in sunny Middlesbrough and I'm garageless. Looks like i'll have to open the wine instead.
Ah, well if you'd said that earlier I could have come and hit it with a hammer for you instead of going to the pub: I'm just across the river
wedg1e said:
The Guinnster said:
If this was top trumps it would be great, " 8 cylinders and 5 temperature sensors!" I'm getting confused now. I can't even go look as its pouring down in sunny Middlesbrough and I'm garageless. Looks like i'll have to open the wine instead.
Ah, well if you'd said that earlier I could have come and hit it with a hammer for you instead of going to the pub: I'm just across the river
Ah, you've been getting lessons from some of the local "specialists" with there carburettor hammers. Would that be the old "When you're ready, nod your head and i'll hit it!"
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