Peugoet temp sensor and BITRON unit problem.

[indigo200]

Hi everyone, sorry about putting a boring help post as my first post however I am having trouble with my car!

the issue is that my fans don't turn on at all, it the set up with the two fans on the front (with air-con). I have three relays on the front that all work (all brand new and tested), both fans work fine (tested) and the bitron module (again replaced and i think it is working OK).

When I unplug the brown temp sensor on the thermostat hosing the feed to the bitron unit goes open loop and the fans go on full speed. when i turn the aircon on the fans go at half speed (as they should i believe they should) so this makes me think the bitron is working and the fans and relays all works as i get full and half speed working well.

the only thing that is left over is the brown temp sensor now. i make some leads up with some small spade connectors and checked the temp sensor from pin 7 and pin 14 of the bitron module interface (these are the pin that go to the sensor) and at cold i seem to get about 2.2kΩ. at 24c and then 2.7kΩ at 100c. I thought this might be wrong so i ordered a new one.

The new one has come and i tested it in boiling water before i installed it into the car and the new results i am getting are pretty much the same as the results of the one fitted to the car! So is this right or do i have two duds?

What kind of result should i get out of a brown Peugeot temp plug? I thought this was the kind of result range i was meant to expect maybe this is for a green plug.


WARNING after looking around I found this is not the correct data sheet for the brown bitron sensor

I know this set up is the same in allot of cars like the 405, 306, 206, xantia's and others. Mine is a 1995 petrol 405! I would be very very grateful for some help!

I am starting to this i should get a POT (0Ω to 5kΩ) just to test when the fans come on! if anyone knows about the brown plugs please say.

[xantia_v6]

How hot does the engine get without the fans coming on?

[indigo200]

The fans never come on! haha, had the head gasket done this summer!

This is a link to details about the system I am talking about:

http://www.peugeotlogic.com/workshop/ws ... fanop1.htm

Its says "The engine cooling fan system is made up of the following parts. 2 fan motors, 3 relays, control unit and the coolant temperature thermistor (NTC)", So he is saying a NTC so that means the resistance goes down as the temp goes up I believe. I then bought one (part number 1338.55) and like the old one its acts like a PTC one. So I'm not sure maybe the cheap one i bought is wrong however it is made by bitron...

[xantia_v6]

The fans should switch on (low speed) at 95 degrees and switch to high speed at 105 degrees. If your engine is not getting to 95 degrees, then there may be no problem.

[indigo200]

I had a go just now and the results are odd. The unit I got out a xantia (BITRON) does not seem to do anything at all, when it gets hot or when the aircon is turned on. the next unit i have was out of a 206. when this one is plugged in the fans just sit at low speed and never change even at low temps with the aircon off. something is wrong with one (or both) of these units.

Any advice? (thanks for the helping so far) i think i might need a new unit and to be sure i have the correct temp sensor.

I am starting to think I need a bitron out of a 405, not another model.

[white exec]

Have had a quick look on Citroen at similar engine (1.8i), and these show three coolant temp sensors.
This arrangement is common on PSA engines, with each sensor having different R-T characteristics, and NTC/PTC.
Functions include ECU (injection) input, AC control, Gauge feed, Hi Temp Warning feed, etc.

Do check you are dealing with the correct sensor. Someone with access to Peu parts should be able to check against your VIN.

[indigo200]

I got this for my car:


20 I think is for the ECU has only one pin (uses the block for ground i think)

21 is blue and is used for the dashboard gauge it has two pins and when I unplug it the temp gauge no longer works

and 22 is brown or maroon this is what seems to be used by the bitron. The bitron governs you fans, Some AC functions and the warning stop light on the dash.

[white exec]

Yes, you have it right.
#20 is for Injection ECU
#21 for Dial/Gauge
#22 for Bitron . . . shown as 'maroon' on PSA's English language parts pages; should show as Brown (marron)!

Have had a look for R-T figures for the item (part no. 1338 55), but I can't find.
You may be able to call up the test data, as above, and verify whether NTC or PTC.

This same sensor is used for this function on numerous PSA vehicles, and feeds varying resistance into the Bitron cooling control ECU.

[indigo200]

Hopefully! Everyone seems to say it's NTC but the ones I have tested seem to PTC. So I need some information on 1338.55 to rule it out but I can't find any data on it anywhere. I wish I had data for it like in the first post on this thread.

I'm not sure the bitron units are compatible however I feel they should be... I know a exact duplicate of my car that's being scraped. I will see if I can get the unit out that. Not much petrol 405's around anymore!

Thanks for the help though guys, if anyone has anyone technical data it would really help.

[indigo200]

I had a talk with a French car specialist and he told me there is 6 different bitron systems for the 405 alone. I have ordered the correct one brand new from them so hopefully it will be solved! Will update when I install it.

[wheeler]

The green & blue sensors are NTC.
The brown is PTC.

[white exec]

Useful confirmation.
Just out of interest, do you have the resistance-vs-temp figures for the sensors?

[wheeler]

Should have in my archives somewhere, ill have a look tomorrow evening.

[wheeler]

Can only find an NTC chart at the moment:
0 deg = 6000 ohms
20 deg = 2500 ohms
40 deg = 1100 ohms
60 deg = 600 ohms
80 deg = 300 ohms
100 deg = 190 ohms

[indigo200]

I bought the new unit for about £75 new and it made no difference *facepalm*.

The next step was to replace the brown sensor Again. I did this and no difference once again. This time I did some testing. I put the brown sensor in a shot glass filled with water then put that in a pot filled with water and heard it to a boil with a electric cooking gauge. The resistance went up as the heat went up 20c is about 2.2kohm and 100c was 3kohm. I did this with both sensors and results where the same (the new one was made by bitron themselves).

The next step was to check what triggers the ecu so for this I made a test ecu tool. I have always known the pin-outs on the bitron unit thanks to this image:



there is 11 wires on the socket so i counted and sure enough there was 11 on my loom so i guessed this was correct. so i cut open my old bitron unit and de-soldered and removed pins 7 and 14:



I then put a couple wires through and soldered them through:



Then just drilled holes in the top of the ecu, used hot glue to seal it up and used so terminal to make it easy to switch it around:



Thankfully after all of this it still worked! I put it in the car and wired in a 0 ohm to 4.7k ohm POT and played around with it. An important thing to remember is the multimeter messes with the ecu so you need to disconnect the POT before you take readings. The fans would go on full blast under about 1200 ohms. This is the ecu thinking its closed loop and the sensor has failed I guess. It would then go to about half speed at about 2800 to 3000 ohms and would go to full speed not long after ( 95c and 100c). The temp to Resistance line would not be a straight line so i cant work out what it should be at any temp but i can round about guess now!

So the sensor I installed was doing the right job going to the right resistance at the right time and my ECU was working fine. all the rest of the system works fine. this leaves one thing left that might be damaged, the loom. I did not want to modify or cut any parts out the loom so it was a good job i made that test ecu. My plan is just to run a wire directly from the sensor to the test ecu connections. And when i got the car up to 100C tested the bitron sensor through the loom and got 2650 ohms! I get over 1m ohm across the cables but i guess when the supply is there its enough to act like to resistors in parallel!

Sadly my van (work) is being repaired at the moment and it has all my crimps and wire. So I will update you guys when I have wired it all up as it should be.