I have and 2000 astra engine code z18xe. A couple of weeks ago started getting engine coolant light appear. It only ever comes on when the aircon is on. The speed of blowers or temperature does not seem to make a difference. The aircon was still woring pumping out cold air and i could hear the fans running. Engine temperature remains constant evan when stuck in traffic. I found it could take anything from 5 to 30 mins to come on.
I have taken it to the garage to have tech 2 read but they seem unable to pinpoint problem.
Day one :they said that fault was showing as coolant module but not logging in ecu. cleared codes and tried to get fresh reading but nothing went wrong, so could i leave car and they would try again tomorrow.
Day two : when they re-tried showed problem with condensor fan or fan module, but when checked this seemed to be ok. they said they had to leave it running for arounfd 1hr before it did anything. they have said did not want to change unnecassary parts so would try to get a reading whilst engine still running.
Day three : they took it for a test drive until light came up, then put it on the machine, now it is saying the cooling fan is faulty.
They have stated each part would cost around £100 + fitting and have asked what i would like to do next, as the only guaranteed cure is to change all three.
My question is if the coolant module was faulty, would it be throwing up error codes for non existant problems.