No heat -- drivers side 2000 Catera

10-15-2006, 08:54 PM
Hello all,

My son just purchased his first car -- a 2000 Catera with 105K miles. We knew it had some problems (bad rear shocks/fixed already, leaking valve cover/getting manual and will tackle shortly, cracked window/being replaced today) but there was one item the last owner did not tell us about -- problems with the heater. What is happening is that the driver side gets no heat while the passenger side ALMOST always works. I say ALMOST always because there has been a few times where it too would only blow cold air. Both digital controls work fine, going up and down while turning the knobs. I can change from floor to blend to vents with no problem on both. If I turn the passenger side off, I still get heat on the passenger side and cool/cold air on the driver, controlled by the driver-side temperature setting. The A/C works fine on both sides (although once on, there is no way to warm up the driver's side; it just blows either cold or cool air, depending on temp setting). I do know the following parts have been replaced since I got the owner to give me all the paperwork she had: heater core in May ‘06, water pump (March ‘05), heater control valve (July ‘04).

One thing I did look at was the heater control valve, located at the rear of the engine very close to the firewall on the passenger side. When I disconnected the vacuum line to it, I got lots of heat on the passenger side. Someone on another forum thought that maybe the electric actuators were bad, so we took apart the lower section of the passenger and drivers side and found them. The bad news is that both worked -- when we turned the temp up on the drivers (and/or passenger) side, we saw the motor move two rods -- one plastic (which goes up and connects somewhere) and a metal rod that is horizontal for its connection. When we turn the temp down or the car off, they reset. With the car off and the actuator motor removed, I manually moved the connected levers on the driver’s side (which is where we get no heat). I can hear something opening and closing up in the dash. I am guessing it is a plastic door attached to the plastic rod and has to do with the cooling side. I am not sure if the metal rod is opening and closing anything. It appears to NOT be loose but I cannot hear anything move in the area it goes to. In addition, I do not see an easy way to disconnect the rods -- they are attached to a gear box the actuator attaches to. I was afraid to remove this as I assume it 'synchronizes' the two doors. The previous owner did have the heater core replaced this past summer. Is the core in the middle of the dash, or would one have to remove the entire dash to replace it (the repair order said they took 12 hours to replace it and removed the entire dash)? If so, I am wondering if the service center MISSED hooking up the metal rod (which I am guessing goes to a flapper on the heater side) -- since it was done in summer, who would test for heat, right? Does anyone know if my assumptions above are true -- that the horizontal metal rod somehow moves/regulates heat and that it might be disconnected? Any idea how to get to that portion of the mechanism?

As for heat to the entire car, we do have an intermittent problem where even the passenger side does not always get heat. As mentioned previously, it is sometimes necessary to remove the vacuum line to the heater control valve (located very close to the firewall in the engine compartment) for a second and then hot water will flow through the system and into the car. Once reconnected, it keeps working fine. Furthermore, this does NOT have to be done every time – it seems to work for a period of time before we need to remove it momentarily again. I tried to follow this line inside the car but it disappeared behind the center dash (I was hoping to see if it was pinched but no luck). I am guessing it is suppose to bleed off the vacuum to open the valve and let hot water into the heater core.

Does any one have any ideas as to what to try? Any one have answers to any questions above?

Thanks in advance for everyone’s help.

Frank in Michigan

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