Gran Prix GT heater problem

I have a 2000 Gran Prix GT that runs great except for two problems. I bought the car used in 04 when I lived in Delaware, it had around 84,000 miles then. I had the transmission rebuild in 2006 when i started having problems shifting from reverse to drive or drive to reverse. I moved to San Francisco in 2007 and left my car at my sisters house in Philladelphia. Last year I drove the car from Philly to San Francisco in under 3 days. Now the reverse light does not come on when I backup and cold air comes out when I use the heater, never warms up. I’ve checked all the wires, cables, and fuses that I can find from the manuals but have not been able to resolve either problems. What am I missing or over looking? I talked to a mechanic and he said that I may need to get the wiring checked and it cost $350 an hour for their guy to look at it. What should I do to fix the problems with my car?


Assuming the reverse light bulbs are OK and the fuse is good, locate and test the reverse light switch. On manual transmissions the switch attaches to the transmission, but I’m not sure where it is on an automatic. Perhaps someone with more knowledge of automatics will post the answer.

In order to get heat inside the car the engine must reach correct operating temperature. If this is not happening try installing a new thermostat.

If the engine is warming up correctly check the heater core. The hoses leading to and from the core should be hot when the engine is fully warmed up. If one of the hoses isn’t hot the core is blocked and coolant is not flowing through it. Without good flow there won’t be much heat, or none at all.

If the core is hot the problem is in the HVAC system under the dashboard. Interior air temperature is controlled by the “blend door” which directs incoming air through the heater or the AC evaporator, or both, depending on the desired temperature. If the door is stuck in the “cold” position it will not send air through the heater core, and you’ll get no heat even if the core is hot.

Some HVAC systems are controlled by vacuum and some are electrically operated. There could be a problem with the mechanism that moves the blend door, or there could be a physical preventing the door from moving.

If the thermostat is stuck open, and the coolant is not warming up, the check engine light should be on. Is it?

sorry for the delay. no to the above question. as a matter of fact, none of the warning lights are lit. it’s as if the system board thinks theres nothing wrong with the car. but when you turn on the heater only cold air blows out, ac works ok i think havent tested yet.

it cost $350 an hour for their guy to look at it…first things first. Find a different shop. This guy is off his nut.
Check to see there is any coolant at all in the coolant reservoir, without any, it will always blow cold. If it is low you may need to burp the system to get air bubbles out.