2007 S40 2.4i

i bought this car with a blown headgasket and just finished replacing it with a new waterpump and tstat. it was the upper hose that blew and caused it to overheat and blow the gasket.

it runs great now, the temp gauge runs perfectly in the middle (which i think is normal for this car), takes about 5 min to warm up and can idle in the driveway for 30 min....even drove 20 min with the gauge not moving from the middle.

however upon my return trip home on this beatuiful 50 deg day i noticed the temp gauge climbing up a bit...getting about 3/4 of the way but not to the red range. i turned on the heat and the gauge quickly (10-20 sec) drop back to the middle. AC was on and i could hear the compressor short cycling and at that time, i felt the cooling fan spinning slowly, barely moving any air but it was spinning.

i have since tried to duplicate the problem...the AC is short cycling still and the fan isnt coming at all...it still spins free and has 12v going to it...not sure about the trigger wire (not even sure what the signal/triggger wire should read).

i am going to pop in a new coolant temp sensor just because it is cheap and easy but i am not a big fan with throwing parts at things.

how can i let it run for 30 min and take it for a 20 min drive and not have any temp issues and then suddenly have the gauge climb up?

how can i test the fan?

i swear the AC worked the other day when i took it for a quick spin but am now questioning that....the car idle drops pretty good when the compressor kicks in.

could a high pressure AC switch cause the fan to NEVER come on?

i am contemplating bringing it to a shop to hook up the VADIS...which drives me insane to even consider.

please help me figure this out...i thought everything was great last week and the car was finally fixed, now i flustered beyond belief....thanks all!

 

could have an issue with the cooling fan module which only comes with the fan assembly - should have a dtc stored if this is the case

 

Read this thread - could this be your issue. Happened to me. Replacing the resistor did the trick.

http://www.volvoforums.org.uk/showthread.php?t=201942

 

Whoops just noticed that your car is an 07. Not sure if the same thing applies. Just out of curiosity though are you only overheating when ac runs or after 30min regardless of whether it is running or not?

 

Thanks Pierre but my fan isn't like that of the post....it's a single fan that doesn't have any resistors like that. The 3 wires are a 12v, ground and trigger wire...it's the trigger wire coming from the ecu that is telling the fan what to do, the 12v and ground in always there.

Update..I was watching the ect sensor readings last night and think I might have found something. First off, the gauge stayed in the middle from 185-235 deg...kinda weird but ok. I guess Volvo wanted the gauge to stay in the middle. I then tapped on the fan controller (small credit card sized metal box mounted on fan shroud) the Smith suggested was the culprit...a few taps and the fan came on. Temps cameright down and AC stopped short cycling too. There must be something loose or faulty with it, a new fan assy is coming Monday and suspect my problems w be cured. Stay tuned for the update,.,

 

damn - nice work!

 

All is right in the world....cooling fan did it.