Alright everyone- I have one for you. My cars heater was not working so I took it in and had the thermostat replaced now it is throwing hot air out the passenger side but its still cool air coming out of the driver side. What the heck? Evertything else is good, the defrost seems good and the feet but when I switch to the vents its cool air?

Any ideas?

What trouble codes is the heater throwing? Unless you have an early '03 you'll need a professional scanner like a TECH II to pull them.

No scanner to run a diagnosis. No dummy lights on

It is the heater core. 6.6 hours to replace and about 130 bucks for the parts. You should be checking for other things too. Check transmission cooler lines, and all the coolant lines, they MIGHT be causing the cooler to be clogged up.

My 2 Cents. Out.

The heater wont throw a trouble code its not part of the diagnostic system. Its not the heater core because one side is working fine. The trans cooler has absolutely nothing to do with the hvac system. There are temp motors on both sides of the heater core (accessed through the kick panels behind the radio) that control the flaps that allow the right mix of cold and hot air to make up the right temp coming out, one for the passanger side one for the drivers side. Most likely, your left (drivers side) motor is not working correctly and the flap is stuck in the cold position. It can be verfied by removing the motor and moving the flap by hand. The motor is held on by two screws and is not hard to replace and is about a $40 part.

I could be the heater core because I had the same thing happen to mine. I had the core changed and the problem was fixed. Mine did the same, heat on the passenger side but none on the driver. Get them to flush it out and you might get a bit of heat back in the driver side. But it will start doing the same thing after a short time. The reason I said Tranny cooler lines is because the tranny cooler is part of the rad. If there is a leak it will put trans fluid into your cooling system, and might be the thing that will cause the core to get messed up.

What suprane1 is saying could also be the problem. This place is just for info for you to narrow your search down. Here is the info from people that have had these problems. Start with the easy stuff and work your way up.

The heater wont throw a trouble code its not part of the diagnostic system. Its not the heater core because one side is working fine. The trans cooler has absolutely nothing to do with the hvac system. There are temp motors on both sides of the heater core (accessed through the kick panels behind the radio) that control the flaps that allow the right mix of cold and hot air to make up the right temp coming out, one for the passanger side one for the drivers side. Most likely, your left (drivers side) motor is not working correctly and the flap is stuck in the cold position. It can be verfied by removing the motor and moving the flap by hand. The motor is held on by two screws and is not hard to replace and is about a $40 part.
My FSM shows page after page of HVAC trouble codes with the prefix "B" for body module. These are read out with a professional tool like a TECH II.

My FSM shows page after page of HVAC trouble codes with the prefix "B" for body module. These are read out with a professional tool like a TECH II.

Page after page of B codes covering air bags, restraints, door keys, seats, windows, headlamps but only 5 that specifically deal with the hvac and none that will set code if you have a bad temp motor, or a bad heater core or a multitude of other problems with the heater. And yes I have a Tech II and yes I have had this same problem and had no codes.

Make that 12 codes in 5 category's

Make that 12 codes in 5 category's
How can that be if it's not part of the diagnostic system?

The heater wont throw a trouble code its not part of the diagnostic system. Its not the heater core because one side is working fine. The trans cooler has absolutely nothing to do with the hvac system. There are temp motors on both sides of the heater core (accessed through the kick panels behind the radio) that control the flaps that allow the right mix of cold and hot air to make up the right temp coming out, one for the passanger side one for the drivers side. Most likely, your left (drivers side) motor is not working correctly and the flap is stuck in the cold position. It can be verfied by removing the motor and moving the flap by hand. The motor is held on by two screws and is not hard to replace and is about a $40 part.

Will these "flaps" you speak of work lose with warmer weather? If it does not get fixed immediatly could it cause any long term ramifications? Thanks for the help!

BTW- I noticed this moring that I have the same problem with the defrost, passenger side (HOT) and driver side (COOL)

Jason

I have a questions about thermostate replacement.

Did you service engine lite come on prior to therm replacement?

I was informed to change a 3.2 liter thermostate is a 7-8 hour job, and runs about $750.00 labour to replace a $45.00 part.

In colder months my service lite comes on, and it stays on all winter, and I get it reset in spring, its caused by thermostate.

Do you agree with these points.

As for your issue of cold air, have you had a power flush of cooling system?

Thanks

Ted

Yes, my service light was a late indicater for the thermostat and yes it is pricy for a cheap part. I did not go to cadillac, I went to another guy and it took him about 4.5 hours and 450 bucks. I have not done anything but that stat replacement.