Thread: Air Con fan on when maybe is shouldn't be.

Hi Scott,
Yes I did, on the black hose surface and two places where I stuck matt black tape on a shiny surface. Got the thermo off Ebay for about $10.

Cheers Marty

Hi Gents,
Now I feel like I'm getting closer. The temp sensor is that the same sensor that gives the temp gauge read out or is there another sensor? If this is a different sensor where is it? When I have found it what should the resistance reading be across the terminals and if the is more than two terminals which terminals do I check.

Great help thank you.....

Cheers Marty

Marty,the HEVAC system has its own fault finding system.
If you have the RAVE disc look it up,too many sleeps for me to remember how its done,it displays its own fault codes,the results shown are shown on the RAVE disc.
GOODLUCK
Andrew

Hi Andy,
I'll hook up my Faultmate later in the week. Would a low refrigerant level cause the symptoms I'm seeing? I might have to invest in a mobile HVAC guy to come around and check the level, the air con doesn't seem that good right now, rubbish in fact.

Cheers Marty

Originally Posted by Nomad9

Hi Gents,
Now I feel like I'm getting closer. The temp sensor is that the same sensor that gives the temp gauge read out or is there another sensor? If this is a different sensor where is it? When I have found it what should the resistance reading be across the terminals and if the is more than two terminals which terminals do I check.

Great help thank you.....

Cheers Marty

The sensor is the ECT(engine coolant temp sensor) the same which works for the gauge(read again post #3 please, that's why i said about the gauge)... i must insist, the aircon system has nothing to do with the fan operation with ignition off, you dont need to measure resistance of the sensor if you have tester cos the ECM will manage the fan based on the same input which will be shown as coolant temp by the tester so corroborating this with that attachment from my first answer the ECM must get a 110*C input while running to activate the fan and get 105*C or more to keep it running when you turn ignition off then it will turn the fan off after 10 minutes or when the coolant temp input drops below 100*C

so the scenarios:
1. if you turn ignition off and the tester will show less than 105*C at that point you have a more serious problem with the ECU or what's at nr. 4
2. if the real temperature of the coolant is less but the reading is above 105*C the temp sensor is bad,
3. if the reading is above 105*C and the real temp of the coolant the same there is a cooling issue most probably the viscous fan doesnt lock well or something
4. if the fan comes on every time you start the engine even if the outside temp is below 28*C or with aircon swithced off it means theres a high coolant temp fault code stored in the ECM which must be erased

Hi Sierra Wizard,
By George I think you may have got it. When I bought "Jezza" I bought it at a bargain price with a known head gasket problem. I'm betting point 4 at this moment in time is very relevant. I'll get the Faultmate out later in the week and check for fault codes in the HVAC unit. I am assuming the only way to clear the fault is to go into the system and do this, disconnecting the battery whilst I repaired the head gasket for five days won't clear the fault. Thank you.