turbo engine bay temp sensors

Just been doing a bit of tidying up and preventative maintenance etc and notice something "odd" regarding the 2 temp sensors just in front of the turbo.

My understanding was that one cuts in at a medium temp, 60 C ish, and the 2 engine bay fans will start up at 6 volts providing some airflow.

Then when the bay gets hotter, 90 ish, the other sensor will switch the fans to 12 volts and they will provide max air flow at full strength.

So to verify that they are working I unpluged the connectors from the sensors and shorted the terminals together.

- The bottom pair make the fans start up.
- the top pair, do nothing.

- I have tried shorting both at once as well as 1 pair and then the other (both ways) and all I get is the fans at 1 speed when the bottom pair are shorted.

Is this normal, or should I say "any suggestions?".

My top pair make the fans start but the bottoms do nothing
Top wires are 1 yellow and 1 green the bottom wires are both brown so maybe a hint in that
Perhaps it's a resistance switch It supresses the voltage until 90 is reached .It wouldn't work by shorting

Hand made cars, don't we luv 'em !!!
Top pair are white, one shethed in black sleve.
Bottom pair are both black.
Off to find and read the wiring manual, back later, probly much later!
Does any one have a wiring schematics that is less complcated and coded than the Renault factory 77 11 085 673 NT 8047 model year 1989?

Wiring manual scematic no 48, looks like a simple loom.
Parts manual page 13.321 indicates that top sensor is 110 C and bottom is 80-90 C.
My top sensor is marked as 1VT4AD275F Z5T silver canister with grey plastic insert.
My bottom sensor is marked as 1VT4GB309F 60 10 017882 K0T with a red plastic insert.
Both manufactured by KLIXON, seen between the terminals.
these part nos do not match with the parts manual for D501 or D503 on following page.

I think i'll pop them into a pan of water and bring it to the boil and see what temps they switch at while monitoring their resistance. While cold, they are both open circuit.
Will have to wait till the kitchen is empty.

lee, what sort of thermometer did you use for engine bay testing? and how and where did you connect it as I might resort to just letting the engine bay heat up and monitor the fans supply voltage.

have I got this right???
In the wiring book, schematic 48 shows a relay at the top of the page, labeled 13. Is that the one on page 215 / S7 which is situated inder the radio.
COR, it might be becoming clear now????

lee, what sort of thermometer did you use for engine bay testing? and how and where did you connect it as I might resort to just letting the engine bay heat up and monitor the fans supply voltage.

http://rswww.com/cgi-bin/bv/rswww/subRangeAction.do?cacheID=ukie

It only goes up to 70 C though ,it was good enough for my plenum readings as it was the cold side I was testing .The hot side would max out sitting in traffic .

There are 3 temperature sensors that operate the fans.

Sensor 1 is located in the sump. This starts the fans at 6 volts if the oil temperature is above 60 degrees.

Sensor 2 is on the post in front of the turbo. This operates at 90 degrees and the motors rotate at 12 volts.

Sensor 3, with the ignition off, if the engine bay temperature exceeds 110 degrees this starts the fans.

The 6 volt resistor is located behind the radio on the passenger side. These are prone to failing but most people are unaware as the fans run at 12 volts when the car is switched off.

Oh how these french electrics can be so challenging, just to understand, never mind work with, But obvious and logical when you know what you are doing.

Thanks, I'll have a look at the sump sensor and check it out over the weekend.
I found a relay like device in the drivers side, seems to be item 13 on diagram 48 of the wiring diagrams.
Inside it "sort of looks" like 2 relays and it has 4 contacts in the same configuration as the wiring diagram. Is the resistor in this or something seperate, on the passengers side, ...... somewhere?

Am I right in guessing that the 110 C sensor will be the one that illuminates the dash warning light too?

Also, which sensor should be top/bottom on the post, the bottom one has a shield in front of it from the turbo.

Thanks again.

I have done some work today to check out these sensors and see when and how they operate. My car is an 86 example, so it may be different in other cars.

First I took the 2 engine bay sensors out of the car. With each one I connected a multimeter and hung them in a pan of water with a digital thermometer probe.

The bottom sensor, with red plastic, closed at 85 C, I heard it click quite loudly, and as I added cold water, it reopened at 70C. I did this again and got the same result.

When I tried the Top sensor, the water reached 97C and did not close. No vegitable oil in the kitchen so I'll have to measure this one another time.

On the car I wedged the probe against the sump case with a piece of wood. I disconnected the oil temp leads and put a multimeter accross them, when cold it is an open circuit. Started the engine and waited, for quite some time. Eventually the oil temp switch closed and I cut the ignition. The temp rose a bit more, from 41 up to 45 C. So I'm guessing it is closing at 50 C ish as the probe was not actually in the oil.

Now I reconnected the oil temp wires and started the car up again.
The fans were on at a slow speed. When I short out the leads for the bottom sensor, simulating it reaching 85C the fans switched up to full blast. When I short out the top sensor, The Turbo warning light on the dash came on.

When I switch the engine off, The fans stay on for 3 mins at full blow.

If I simulate a cold engine, by disconnecting the oil temp wires, when I switch the engine off,.... no fans at all.

To simulate a HOT motor after switching off, I shorted the wires to the top sensor, nothing happened not even the turbo warning light came on, because the ignition was off. Then I shorted the leads to the bottom sensor and the fans came on full blast for 3 mins. In this test it does not matter what the oil temp is in the sump.

Out I went for an hour, some very spirited driving, lots of on-boost and later stopped in a lay by. WOW... as I did not have the engine cover on and in the mirror I could see the heat radiating up,looked like a film of oil was burning too. On closer examination, YES that turbo was hot, very Hot, and the fans were on, but they did not seem full blast. I pulled back the leads on the bottom sensor a little and shorted the terminal together and the fans then came on full blast.

SO, the turbo was not hot enough to trip the lower sensor. I don't beleive it!

I have now made up a bracket to reposition the bottom sensor where it will receive more of the turbo's rediated heat. I'll test it tomorrow and post the out come. I don't see any harm in having the fans on at 12 volts, they will suck a lot more heat off the turbo.

ps: any one know why the sensors' grommets say "do not reuse" on them?