Hi. wondering if anyone can help. 1- cooling fan works but does not turn on when hot. 2- cooling fan sometimes turns on when cold just when key is on and then for a little while. 3- engine surges. 4- will not restart or very hard to start after enginr running for a while. Temperature gauge erratic. jumps to hot for a secon or two when cold then registers cold when engine is hot.

Cooling system is full. Thermostat is opening. Changed the temp control sensor. Fans work when A/C turned on. No check engine light coming on and no codes.checked plug connectors.
I dont where to go next...Anybody???

 

You could have air trapped in the cooling system (I'd try idling it to full temperature with the heater on hot and the expansion tank cap off for a while). Or possibly a stuck thermostat.

The the temperature gauge going up and down erratically normally indicates low coolant (where the coolant level drops below the sensor, so the gauge and the fans don't work correctly). The scary thing is that it sounds like the engine is getting really hot (by virtue of it not wanting to start after it's been running).

 

thanks. I'll let you know how I make out.

 

I got a bad coolant temp sensor straight from the auto parts store. Replaced it with a genuine Volvo part from the dealer and everything went back to normal.

 

also the connector to the ECT can be finicky - lol first time took me 15 minutes just to figure out how to unhook... I agree with Hudini in that it may be the replacement part or can be how it was connected. not sure if it pulls ground off the housing but you may want to try cleaning the threads when reinstalling.

 

Have you checked the coolant return feed to see if you have good circulation?, this could possibly be a water pump issue.
check for any small splits in the pipes which could also lead to loss of circulation.