I have a 2000 Jeep Grand Cherokee Limited 4.0L engine. The A/C and heat blows fine, but usually will not switch from A/C to heat or vice versa. Sometimes, since it's a dual zone climate control system, it gets stuck on heating one side and cooling the other. I checked the blend door and it is not cracked, bent, or at all broken (possibly replaced by previous owner). I replaced both blend door actuators while in there and put it back together. It's still acting the same.
Previously, I had a problem with the blower motor not running. I replaced the resistor with a used one and haven't had a problem with the blower since then.
Check for a vacuum leak, it may have a bad hose coming from engine and not giving enogh vacuum to operate the actuators.
December, 28, 2012 AT 6:58 PM
The actuators are not vac operated. Thanks though.
December, 29, 2012 AT 2:28 PM
Then see if they are getting power and pull the hvac fuse for 60 seconds as they may reset. Our manual said they were but it can be wrong.
December, 29, 2012 AT 4:27 PM
Sorry I forgot to mention that I already checked that before. They don't always get power. I can adjust the temperature and nothing comes up on the voltmeter. 5 minutes later I'll get a reading when I adjust the temp. It will work a few times, and then stops working again. I have pulled that fuse and reset the system too. It worked ok for a few minutes, and then stopped again.
December, 29, 2012 AT 4:44 PM
If you have a pro tpe scanner see if you can scan it ornot for any codes, it may be a control head problem then.
December, 30, 2012 AT 2:31 PM
I don't have any scanner but I pulled the codes using the built in method. It gave me code 54 and code 56 (basically pointing to a failure of the blend doors to move properly). I disconnected the battery for a few minutes, reconnected it, set the controls to auto, and then turned the key on to recalibrate it. The codes came back again. I've already had the blend door and actuators checked.
December, 30, 2012 AT 2:43 PM
Only thing I can tell yo uis to check for a shortin wiring. Or linkage messed up etc. Or temp door bad. Iknow it'snot much info but that is all we have. It's the same thing for both doors.