10 replies to this topic

[kangaroomadman]

I have a problem on my 2000 MPI at the moment which is running the radiator fan constantly and I am assuming is in 'Limp Home' mode as it's not running particularly well...

 

I had thought the CTS was at fault but tested the resistance and it was giving reasonable values from cold and hot when probed with a multimeter. I also checked the connectivity from the CTS connector back to the ECU connectors and that was also fine. One thing I didn't check was the quality of the connection between the CTS connector and the sensor itself so I assumed this was at fault and bought the modified connector from minispares and fitted it this afternoon but the fan still comes on

 

I know that a coolant sensor failure will cause the fan to run constantly and the car to run in 'Limp Home' mode but is the fan running constantly caused specifically by the CTS failure or will it always run in 'Limp Home' mode. i.e. another sensor failure could result in the fan running constantly?

[FlyingScot]

The modified loom section is to avoid the cable being pulled when the car is in use. There is no magic to it, that section was too short on the original and with movement it stresses the connectors.
Typically the fan runs when the ECU measures the resistance as above a certain level, on a working car pulling the connector off will simulate this. Poor connection, poor earth duff sensor will all result in the same.
Maybe someone near you can lend you a diagnostic to read what the ECU sees?
Not aware of another fault which when logged causes the fan to run constantly.

FS

[ukcooper]

http://www.minispare...ch/classic/twin point.aspx|Back to search

[kangaroomadman]

That's what I fitted this afternoon.

Interestingly the fan doesn't come on immediately but only after a few minutes. I just started the mini and the fan wasn't on- unplugging the CTS caused the fan to come on immediately.

Could it be bad readings from the CTS that make the ECU think it's over temperature? But then wouldn't the temp gauge show this? Currently the fan comes on before the needle can even get to the blue mark!

[Sprocket]

Typically when you open circuit (disconnect) an NTC thermistor is 'reads' low temperature. The dead short and open circuit values of the thermistor are predefined in the ECU to be able to activate the limp mode and substitute the 'false' value with a predefined fixed value. A cold engine may be difficult to start, and a warm engine may run rich. I'm not sure if the ECU also modulates the coolant temperature gauge to the predefined limp value if the CTS is in fault. Normal running temperature is normally on the mid way white line (assuming the correct thermostat is fitted. The limp value would be nearer the blue.

For what it's worth, if you don't have access to diagnostic equipment, I would replace the sensor as a matter of course. Wiring is obviously a factor too.

[kangaroomadman]

Last week I was coming to the conclusion that I have a break in the loom that is causing bad readings for some of the sensors as I do have a bit of engine movement at the moment which could have damaged the loom. Last Thursday the car was driving terribly coming on/off throttle as if the TPS was completely broken - it was terrible! Friday was a complete contrast and drove really nicely again, holding revs coming off throttle and pulling away nicely. Both days the fan was still on though.....

 

So I bought myself a diagnostic to see what's going on. I connected it up last night and first off read 6 faults:

• 06 MAP Sensor Circuit
• 11 Battery voltage too low
• 01 ECM Supply
• 02 Coolant Temperature Sensor Circuit
• 07 Inlet Air Temperature Sensor Circuit
• 08 Throttle Potentiometer Circuit

At this time the readings from the sensors looked sensible so I cleared the errors and set off home, monitoring the sensor values on the diagnostic. All the way home the coolant values looked sensible, however, the fan did come on again after a minute. The temperature slowly climbed and settled around 90 degrees.

 

When I got home I read the fault codes again and got the following new faults:

• 02 Coolant Temperature Sensor Circuit (Sensor output)
• 16 Coolant Temperature Sensor Circuit (Active Fault)

So this is obviously the cause of the fan coming on but I think my break in the loom is further round than normal as I've replaced the usual culprit, and it also seemed to be effecting the TPS last week as well.

 

As a first step I will try and get the engine more stable - The bushes (rubber) are only about a year old so should be OK but I will check the bolts are tight. Once I get that stable I'll have to look for any pinch points on the loom and repair as necessary.

[Steve220]

Which diagnostic kit did you get? As standard OBD systems can't pick up mems faults.

[kangaroomadman]

ACR4 with Rover 3 Pod

[kangaroomadman]

Yesterday I found that my lower engine stabiliser had come loose. I couldn't move it with my hand easily but the bolt was definitely loose.

 

Tightening it up made the engine feel steadier and I was hoping would stop the fan coming on (at least for longer in to a journey) as the loom would be moving around less, however, it came on only after idling for about a minute so even the idling movement can cause a break in the CTS connection.

[kangaroomadman]

A small update on this.....

 

I bought a new coolant sensor and the problem went away! Hooray! ...... but only when starting from cold.....

 

When I start the mini up first thing in the morning it's fine, no faults observed and the fan doesn't come on, however, if I use it again within an hour or two then the fan comes on instantly! There are no faults reported on the ACR4 and the temperature readings are normal so it's not overheating.....

 

I did also notice a problem yesterday when parking and I almost stalled the engine - I just about recovered the stall but the fan kicked in! I didn't have the diagnostic connected but it shouldn't have been too hot as it was only a 5 minute journey.

 

Is there an engine startup condition that won't log a fault but will cause the fan to come on permanently?

[mini13]

what does the rad look like, I have seen similar stuff happen on coroded rads, or ones with blocked cores, basically they get less efficient so the temp in the rad goes up, but they are still good enough to keep the engine cool,

 

might be worth back flushing the rad  and heater as a matter of course.