2009 Chevy Malibu 2.4 off and on temp Gauge on C, No AC and fan comes on right away

Question

My Chevy Malibu (2009 2.4) is acting a tad whacky! It either acts totally normal, or all below occurs at the same time. . .

1) coolant fan(s) come on when I start car 2) temp gauge stays on C (dead) 3) AC does not kick in (blows air with no AC)

This happens at random as best I can tell. But when it happens, it might continue for a day, or half a day and then back to normal. The temp gauge is either dead cold or normal . . . never hot. When it works, the AC blows perfectly cold.

Thoughts?

COuld loose gas cap be an issue? (Seems like mine doesn't really tighten, it clicks and stays slightly wiggly)

Could battery terminal corrosion be the culprit?

Thanks!

Dino

Answer 1

This sounds like it could be faulty wiring to the engine temperature sensor or faulty sensor itself (less likely). In some vehicles (quite a few GM vehicles I know for sure), if you were to pull wire(s) which goes to the engine temperature sensor which relays the engine heat information to the computer, the computer will force the fans on high. This ensures the engine is protected against over heating because the computer doesn't know what the actual temperature of the engine is. This would hold true if the sensor was not transmitting back to the computer for any reason. Also, this would be an indication why the dash gauge would not show any movement while the engine is warm/warming up. I'm not sure about the A/C, but surely this is all related. It would also seem logical in that the computer could keep the A/C from running (engaging the compressor - especially considering the computer controls this signal as well) to help protect the engine as well.

UPDATE: While I don't know for sure, the sensor should be located in the engine around the point of where the top radiator hose goes into the engine. It will have a two wire lead (clipped) connector going into it. The base of it (where it screws into the engine) should be brass in color. Should not be hard to spot, but look at the wiring which is associated for any fraying or cuts. Also, pull the connector to ensure no dirt build-up, moisture, corrosion, etc.

Answer 2

This is a sympton of a faulty 'mapped' cooling system. When the vehicle is cruising, part of the cooling system is closed off by an electrical engine thermostat. This is allows the engine to run a little hotter, say 96 degrees against 90 degrees. This allows adjustments to timing and mixture to use less fuel, which allows lower fuel consumption and less emissions. The system is monitored by two sensors. One sensor monitors the rad water temperature going into the rad, the other the rad water temperature coming out of the rad. The rad out should read lower then the rad in. If any of the sensors read implausible or the rad out is not lower then rad in by a mapped amount, then it is seen as a overheating situation and the cooling fans come on, very shortly after, or when starting the engine and they run all of the time.

Answer 3

This is an open thermostat. I’ve had to replace mine 4 times now. The rubber gasket comes off and sticks inside the thermostat and does not allow it to fully close when cold. The computer detects that is open on a cold start by temperature upstream and downstream. The computer shuts down the temp gauge, kicks on the a/c fans at the radiator and disables the a/c compressor. It’s very random ... sometimes it’s an issue at startup and sometimes it’s not. I’ve tried ac delco and after market parts and have had problems with both. Had problems on 2010 Malibu but none with 2012. Seems like a poor design or bad elastomer on thermostat. Originally thought it was the temperature sensor and replaced it first but that did not fix the problem.