306 Cooling fan and STOP light

[toadmussen]

Hi guys,

Having an issue where the cooling fans run on low speed for about 5 minutes after turning the engine off. The dash STOP light is also coming on after driving for some time. If I stop and let the car cool down, the STOP light goes off. When I did this I opened the radiator cap, coolant looked fine (no boiling/steam). Was a hot day with some traffic so I drove it home by disconnecting the brown sensor to force the fans to run high speed - the STOP light did not come on, however the fans still ran for about 5 minutes after I turned off the car.

The temperature guage on the dash is below 90 deg when the STOP light is coming on, and doesn't go over that.

When I disconnect the brown sensor on the thermostat housing, fans are low speed for a second and then run high speed. I replaced the brown sensor about a year ago (in error at the end, problem was fan was worn out). Connections on that and the other sensors there look clean and ok. Earth points under the battery and down under the enging (gearbox?) look ok.

I have read some posts about wiring looms causing problems. The connector uder the fans on the passenger front side doesn't look to be in great shape.

All levels are ok - coolant, oil, brake fluid, power steering fluid.

It's a 2000 Phase 3 XT with a 2.0 lt.

Any thoughts on where to next? Could it be the Bitron fan controller (mine has a cartier branded one)? Or the wiring connector? Or a faulty temp sensor?
What's the downside to driving it with the brown sensor disconnected (to force high speed fans)?

Thanks!

 

[toadmussen]

Here is a picture of the connector.

 

[AlexB]

The blue sensor on thermostat on some 306 has just a single pin and shorts to ground when temp too high and lights STOP, on others it has 2 pins and possibly behaves differently.
Have you had A/C regassed? The A/C pressure switch also will trigger high speed fans when the pressure exceeds 19 Bar and disables compressor clutch when over 26 Bar (and below 2.5 Bar).

 

[toadmussen]

Thanks for your help Alex. The blue sensor on my 306 has two pins - to me it looks ok?

Re the A/C. I had it regassed a few months ago. Recently the A/C has started to become weak and cold/warm. I suspect it is losing gas and needs another topup. I don't quite understand what you are referring to with the pressure switch?
Note the problem is that the low speed fans come on for 5 mins after switching off the engine.

Today I drove with the brown sensor disconnected (forcing fans to high speed). The stop light never appeared, however the fans still ran on low speed for 5 mins after turning off the car.

 

[lowpugV2]

The fans running on low speed after the engine is switched off is normal if the car has been running warm or been in traffic. When I used my XSi for commutes it would do this when I parked at the office.

I can't explain the STOP lamp coming on. Sound like a faulty sensor

 

[lowpugV2]

Is there definitely coolant circulation? When was the water pump last done?

 

[COL]

I would be hooking up an OBDii analyser and look at the live data for the temp sensor to see if its reading correctly.

There are usually 2 temp sensors, one for the temp gauge and the other for the engine computer.

 

[toadmussen]

Thanks for the replies.

Lowpug - The water pump was replaced in November last year. What's the best way to confirm that is ok?
The fans running after the enging is turned off has only started happening recently, which makes me think something is wrong (I've had the car for 12 years).

Col - I tried my OBD2 reader that was in the 308 (OBD Link MX+) however I can't seem to connect it on any of the protocols. Perhaps it needs the Peugeot tool? However I'm not clear on how this will help the troubleshooting, as the temp guage on the dash does move (starts low, goes up to 90 when driving). It just doesn't go what I would think is high enough to trigger the stop light (it's not going over 90). I assume the scanner would just show the same as the dash?

Wondering if I should get the fan connection looked at, the Bitron replaced or Bitron connection looked at, or maybe even try replacing the blue temp sensor. Clutching at straws here! The car seems to be responding like it thinks it is hot (fan runs after engine off, stop light), however the temp gauge doesn't correspond.

Any concerns with driving around with the brown plug disconnected (both fans constant high speed) whilst I diagnose?

cheers

 

[AlexB]

Re the A/C. I had it regassed a few months ago. Recently the A/C has started to become weak and cold/warm. I suspect it is losing gas and needs another topup. I don't quite understand what you are referring to with the pressure switch?

sorry, cutnpaste finger error, meant to write
A short circuit between the terminals or a break in the wiring from Bitron to the brown sensor sets the fans to high speed and prevents the air conditioning clutch solenoid from operating.

Keep in mind, usually when you have a/c on the low speed fan is also turned on, but when you have lost gas the bitron reads the A/C pressure switch and disables the compressor, and won't turn on the low speed fan even though you'll still have the little green light showing on the A/C button. On my XSi with no gas in system this would result in temp gauge going over 100 before the high speed kicked in, but that's not the symptoms you describe.

Note the problem is that the low speed fans come on for 5 mins after switching off the engine.
Today I drove with the brown sensor disconnected (forcing fans to high speed). The stop light never appeared, however the fans still ran on low speed for 5 mins after turning off the car.

So back to your original post, I can't tell if the photo is of the plug to the fan shroud or one of the two ECU harness plugs on the left chassis rail. It is the smaller of these two that carries the two wires from brown sensor to the bitron unit. The Brown sensor is a PTC (Positive Temp Coefficient) so if these are corroded it could increase the resistance making the bitron think engine is overheating and earth the STOP tell tale light and trigger the post cooling.
Your cartier/phase3 may be programmed differently to my earlier XSi, if I disconnect the brown sensor the fans run at full speed but turn off immediately when I turn ignition off.

I would be hooking up an OBDii analyser and look at the live data for the temp sensor to see if its reading correctly.
There are usually 2 temp sensors, one for the temp gauge and the other for the engine computer.

306 has three, only the VE=Green sensor used by the engine computer can be seen via OBD.
BE= Blue sensor is for the temp gauge AND earths the STOP tell tale.
MR=Brown/Maroon is used by the Bitron fan controller.
The bitron can also earth the STOP tell tale.

 

[toadmussen]

Thanks Alex.
Sorry, the photo is going to the fan.
I traced the one you mentioned from the brown sensor, and pulled apart and inspected that connector (into the chassis) - it looked good.

 

[AlexB]

mmmm, I reckon refit the old brown sensor.
But first measure resistance of brown sensor when cold, reconnect plug and drive till hot and switch off. When fans start the 5min cool down disconnect brown sensor and measure the resistance. Should STOP illuminate disconnect brown sensor and measure the resistance.
I don't think the blue is at fault, parts book describes 1338.09 as Blue 110 DegC which I assume is when pin 2 switches to earth the STOP tell tale.

 

[AlexB]

The fly in the ointment is the cool down feature running for 6 minutes with brown sensor disconnected. I tried a 2001 XSi that should be phase 3 as it has a BSI and with brown disconnected the fans ran at high speed but turned off with the ignition. I don't know whether it has bitron or cartier. The standard 306 bitron has a gray face plate, there is a citroen one with green face plate that turns on low speed fan at a lower temp and runs the cooldown fan for 10 minutes.
Your unit is actually doing all the right things, excepting at the wrong temp.
Brown sensor on my XSi measured
1750 ohms at 20ish DegC ambient
2600 ohms at 70ish DegC on dash
2750 ohms at 80ish DegC on dash

I then fitted a 10K pot in place of the brown sensor and got
2981 ohms Low speed fan
3070 ohms High Speed fan with no cooldown (but sense voltage remains on sensor terminals for 6 minutes)
3160 ohms High Speed fan and then low speed cooldown for exactly 6 minutes
3300 ohms High Speed fan and then low speed cooldown for exactly 6 minutes
3306 ohms High Speed fan, STOP tell tale and then low speed cooldown for exactly 6 minutes

To further isolate down to sensor, harness or bitron you'll need to measure the sensor resistance with plug disconnected, reconnect sensor and then with bitron/cartier disconnected measure the same sensor resistance between pins 7 and 14 on its 15 pin harness plug. Should be the same, if not then problem with wiring/connectors/corrosion etc. Where are you located? Could swap out bitron unit if near Sydney.

 

[toadmussen]

Thanks very much for doing these tests.

I have put a multimeter on the brown sensor and got similar readings to yours.
I then pulled the plug out of the bitron, and measured the resistance between pins 7 and 14. It was the same as direct to the sensor, so the signal seems good from brown sensor to bitron.

I had the car A/C regassed a couple of days ago. Technician didn't find any major gas leaks, worked beautifully driving home, and no stop light, fans didn't run on.
Driving the next day the A/C wasn't cold, back to stop light coming on occassionally, and fans running on.
A/C now is sometimes cold, sometimes not.

I found the old brown sensor, and have put it in. Will take it for a couple of drives to see if that makes any difference.

 

[toadmussen]

Hi all,

Thanks for everyones help - the 306 is now running well, so thought I'd leave a note to help the next person.

The car stays around 90 deg C when driving, the fans turn off with the car, the stop light does not come on, and the A/C works well.

It seems my problem may have been moisture in the connector going to the Cartier/Bitron. I pulled the connection apart, it looked to have a tiny bit of moisture in there, let it dry out, then put it back together. After that, it's been perfect. Was either a tiny bit of moisture, or just the action of pulling it apart and putting back together fixed it.

Thanks.

 

[lowpugV2]

Good news