: No Heat Driver Side -- any ideas?



FM-IN-MI
10-10-06, 10:20 AM
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 (I believe) 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 (remember, I said I usually get heat here, especially when I cycle the temp from low to high to low...). However, for the past few days, I have been getting heat to the passenger side without playing without this valve so maybe this is a red-herring observation.

Both heater lines (going into and out of the core coming through the firewall on the passenger side) are very hot when the engine is hot so I don't believe there is a plug in the core (especially since it was recently replaced).

So, what might be wrong? Are there 2 header cores and is the driver's side one plugged? Are there separate heater 'pumps' on the 2000 (I read were someone says there are aux water pumps on the 1998 Cateras and I see two, small in-line cylindrical devices that appear to be attached to hoses that are heater-sized, one toward the front of the car by the radiator on the drivers side, one further back from the radiator on the passengers side) and the driver's side one is bad? Could there be a hose disconnected that controls the driver's side heat “controller” (e.g. door, flap, flow valve, whatever that might be), especially since the heater core was recently replaced (maybe that dealer did not hook it up correctly/missed/pinched a hose)? Is there a lack-of-vacuum issue (I do seem to get more heat when the car is at a higher RPM then at idle, which is 600RPM – however I do know that at lower RPMs the water pump will run slower/push less water)?

Anyone have any suggestions? Thanks a lot, especially from my son who cannot afford to take it to the dealer.


Frank

contourbs
10-10-06, 02:48 PM
there is 2 blend door actuators. 1 for each side. i would replace them both

wamanning
10-10-06, 09:12 PM
might also be a bad temp sensor. there are 2, 1 each on the driver and pass side somewheres beneath the dash.

my pass side blows cold...i need to run that side at least 5F warmer to get them to blow the same temp.

FM-IN-MI
10-10-06, 09:17 PM
there is 2 blend door actuators. 1 for each side. i would replace them both

Great. Thanks for the suggestion. Have you does this before? Are they hard to get to? I am getting a 1998 Catera service manual shortly (couldn't find a used 2000 one -- only new for $149 so had to pass right now). Do you have any idea if this part of the car remained with the same design?

Lastly, are they driven by vacuum, air pressure or DC (I am wondering if I can rebuild them versus buying new ones)?

Thanks a million!

Frank
Michigan

FM-IN-MI
10-10-06, 09:21 PM
might also be a bad temp sensor. there are 2, 1 each on the driver and pass side somewheres beneath the dash.

my pass side blows cold...i need to run that side at least 5F warmer to get them to blow the same temp.

OK on the sensor. That too is a good suggestion. From what I can tell when I dial the driver's side down with the AC on, it seems to turn the AC on. If I set it higher, it turns it off (relative to the interior temp on the drivers side). Based on this observation, I would tend to think it was working OK, unless there are sensors for both the AC and the heat. What do you think?

Thanks.

Frank

wamanning
10-11-06, 09:01 AM
...unless there are sensors for both the AC and the heat. What do you think?


tech books only show a single pair of temp sensors. the temp sensors may be working, but out of calibration.

walter in motown
GO TIGERS!

FM-IN-MI
10-11-06, 09:30 AM
tech books only show a single pair of temp sensors. the temp sensors may be working, but out of calibration.

walter in motown
GO TIGERS!

Hmmm....

If that would be the case (out of calibration), then wouldn't the A/C fail to turn off when I adjusted the temp above and below what the interior of the car is at? If I switch from heat to A/C, and adjust the driver's side temp control, I can 'feel' it going from very cold (if I set it to, say 60 when the interior is 70) to blowing just air (outside temp) when I set it to 80. The latter of course takes a minute or two as there is no heat on the driver's side and it needs to 'warm up' the cold core.

Also, when I turn the passenger's individual control to 'off' (so that it is controlled off the driver's setting), the passenger's side vents do cycle between hot and cool based on the driver's temp setting (relative to the temp in the car).

Based on the above, I get the feeling that the temp sensors are working relatively correctly. Would you concur? If yes, then I am leaning to the problem being the blend door actuators mentioned by contourbs. Just need to find out what they look like and how to get to them...

By the way, what tech book do you use?

Thanks a bunch.

Frank in Michigan

wamanning
10-11-06, 09:44 PM
there is some special HVAC control combo sequence that resets/recycles the blend door actuators, such as after the battery has been changed. it's either in the owners manual or the big servicing book-set.

edit: just found it in the book.
1. turn ignition to RUN
2. press AUTO and OFF HVAC buttons simultaneously for > 5 seconds
3. stepper motors will cycle thru various positions to recalibrate their operation

FM-IN-MI
10-11-06, 10:54 PM
there is some special HVAC control combo sequence that resets/recycles the blend door actuators, such as after the battery has been changed. it's either in the owners manual or the big servicing book-set.

edit: just found it in the book.
1. turn ignition to RUN
2. press AUTO and OFF HVAC buttons simultaneously for > 5 seconds
3. stepper motors will cycle thru various positions to recalibrate their operation

Hi Walter,

Thanks for finding this -- I did search the owners manual after reading your first posting and all it had was how to reset the moonroof after a battery disconnect.

I did the above and indeed I heard vents/motors/etc moving. Unfortunately, I still do not have heat on the drivers side. It is looking more and more like one of the actuators. Which I knew how they worked (vacuum/DC/air pressure) and where they are located. I won a 1998 Catera Service manual on ebay a few days ago. Hopefully the info will be in it (or someone who reads this will chime in with the answer).

Also, my ride home today was cold. No heat on eiither side. While the engine was running, I removed the vacuum(?) line from that heater (control/flow ?) valve at the rear of the engine, then reconnected it and , voila, heat started to come out on the passenger side. I have turned the engine off and on several times since and heat still is flowing. Mind boggling!!! I am starting to wonder if I have a vacuum leak or plug somewhere (again assuming these parts are vacuum actuated) and this is why I am having an intermittent problem.

Once again, thanks for your help. Feel free to keep suggesting!

Frank in Michigan

FM-IN-MI
10-14-06, 02:47 PM
there is 2 blend door actuators. 1 for each side. i would replace them both

We took apart the lower section of the passenger and drivers side and found the actuators you mentioned. The bad news is that both worked -- when we turned the teimp 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 drivers 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 'syncronizes' 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 repace 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? Do you 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?

On the passenger side we found a vacuum-driven motor on what appears to part of the heater blower assembly (based on its location relative to the heat hoses coming in through the firewall). As the temp was changed high to low, we could also see this 'flapper valve' move back and forth so this appears to be working correctly.

We were not able to see where the vacuum line from the heater control valve (engine compartment) attached -- it went behind the center of the dash along with another hose. I was hoping to see if it was pinched but no luck (sometimes we need to disconnect this hose so that vacuum is relieved so we get heat).

Any way, it appears the garage that worked on this car did NOT know what they were doing. We found broken parts (e.g. they tried to force them off because they did not know the part was held on by screws), damaged plastic and stripped bolt heads.

Once again, thanks for the suggestions and help.

Frank in Michgan

mach1456
10-17-06, 04:21 PM
I have had a problem with this also. Mine would blow hot air on the drivers side and cold on the passengers side. Today I tackled the problem and found the motors that blend the air were the problem, for the most part. This motor has a small gear type piece on it that was not engaging. I pulled both motors off, put them in a vise and pressed the rod back into place. Installed the motors and they both work great. While installing turned heat to 90 and pulled connecting rod down all the away with motor plugged in and car running. To set it in proper position. Also one to the black plastic rods had come off the actuator this was also causing a problem. The vacuum hoses didn't seem to have any effect on the temp. My Catera is a 97. Hope this helps some, good luck.

FM-IN-MI
10-18-06, 10:53 AM
I have had a problem with this also. Mine would blow hot air on the drivers side and cold on the passengers side. Today I tackled the problem and found the motors that blend the air were the problem, for the most part. This motor has a small gear type piece on it that was not engaging. I pulled both motors off, put them in a vise and pressed the rod back into place. Installed the motors and they both work great. While installing turned heat to 90 and pulled connecting rod down all the away with motor plugged in and car running. To set it in proper position. Also one to the black plastic rods had come off the actuator this was also causing a problem. The vacuum hoses didn't seem to have any effect on the temp. My Catera is a 97. Hope this helps some, good luck.

We did find the two DC-powered actuators and tested them. They both worked and the gear-drive they attach to moves two separate control rods, one plastic and one metal. I am starting to believe that the metal one goes to heater flap door and either fell off or broke off. This flap door controls heat to the drivers side and is somewhere below the radio. I am at a loss as to how to get to these parts -- even the service manual does not detail how to get to this flap. I also think I have a problem with a vacuum-operated actuator. The service manual talks about this controlling the heater control valve located in the engine compartment by the fire wall. Sometimes I must disconnect the vacuum line to allow heat to flow into the heater core, otherwise I get no heat on either side. Again the manual talks about this actuator but does not tell exactly how to get to it. When I bought the manuals I had hoped for this information to be well-detailed but it is not.

Thanks for you comments. If you did happen to take apart the center dash, can you give some hints as to how you did it?

Frank

cad73
10-29-06, 07:20 PM
Hi...I have the same issue on a 98 Catera. Does anyone know where to purchase these actuators and also about how much they would cost? Is the installation difficult? I've purchased service manuals and they seem to be pretty thorough. Thanks