VT Thermofan problem

[dodgie12]

Hello I have had my VT 1999 Berlina Wagon for many years with few if any problems except fair wear & tear stuff.A few weeks ago for no apparent reason the temp guage rose to hot with indication flashing and when investigating I found lack of coolant.I have flushed the radiator and renewed the coolant and found no leaking with the coolant level now staying at its normal level. My problem is that when I turn the air con on the thermofans do not start as they always have.There is some talk about high & low speed fans but in my vechicle both fans have come on at what appears to me to be high speed since I have had the vehicle and have never had an overheating problem.In testing ,shorting relay terminals 87 & 30 on low speed relay has no effect.
Shorting terminals 87 & 30 on the high speed relay brings both fans on at full speed.Disconecting the lead to the coolant temp sensor and running the motor for a short time brought both the fans on. Thinking this sensor may be crook and it was fairly cheap I have replaced it but still have the same problems.I have had a look at the main board and can see no visual faults there and also nothing around the relay ecclosure.Without the air con on and letting the car idle for some time the temp guage rises but no fan cooling comes on. With the air con on after the temp guage reaches its normal position the thermofans come on for 3 seconds and off for 15 seconds and seem to continue like that maintaing normal guage position. Coming into summer I don't want overheating problems. Any suggustions where I go from here?

 

[som]

Sound like they're working just fine.I far as I'm aware both fans operate at low speed and again,both fans operate at high speed.My Exec has never become hot enough for the fans to come on at low speed for more than a few seconds,just like you described off/on/off etc and they only come on at high speed when I turn on the A/C.They've been working like that for 445,000km and my car has never overheated.Providing your radiator,heater core,water pump,thermostat,heater tap and "radiator cap" are in good nick then I don't think that you have a problem other than working out why your coolant became low in the first place.I think that you must have a leak somewhere so I'd be going to whatever lengths necessary to find it.Good luck.

 

[dodgie12]

Thanks. But as I mentioned my fans do not come on when I turn my a/c on as they always have done even from dead cold. Also travelled 425,000 k/m. I use the a/c 99% of the time so I have noticed them running.I have also noticed over the years the fans stop when the a/c cycles off and comes back on when the a/c cycles back on again no matter the motor temp. Now the fans only run intermittently as described and never with the a/c off.

 

[FATMOE]

Your fans should always operate once the ac is on. Have you checked your relays and fuses?

There known to stuff up and are always the first things to inspect. Does your ac even work, does the compressor kick over?

 

[dodgie12]

thanks. The a/c works ok and kicks in normally. Have checked fuses and swapped relays with no change

 

[FATMOE]

Have you tried using another thermo fan, the motors on them could be faulty and playing up.

 

[dodgie12]

Thanks Have not tried another fan because if I disconnect the coolant temp sensor and start the motor the fans come on after about 10 seconds. I would then assume the fans are ok and have changed the coolant temp sensor

 

[som]

Sorry mate,missed that at the start of the thread.Hopefully not,cos it's a pain in the butt but I had a similar problem earlier this year which was fixed by replacing the BCM.I also had an airbag light that no matter how many times the error was cleared would end up coming back on.That too was solved when the BCM was replaced so I obviously had more of a problem than you appear to have.Good luck.

 

[dodgie12]

Thanks Bom. Pardon my ignorance. I am abit of a dummy when it comes to motor cars. I guess a BCM is the computer LH passanger side. Sorry Som not Bom

 

[Cheap6]

Sound like they're working just fine.I far as I'm aware both fans operate at low speed and again,both fans operate at high speed.

There was a running change in VT that meant the fans went from both operating at high and low speeds to one on with "low" speed and both on with "high" speed switching.