Now its the AC

Hello,

The AC is blows cold then suddenly it goes hot. After the car sits for an undetermined amount of time. I can return to drive it again and walla! the the AC is back to cold. This has happened a couple of times last summer but I just ignored it becasue it doesnt happen often enough. Now its happened twice already and its only the first day of spring. Whats causing this please?

Could be a couple of things happening here...

If the car has an automatic thermostat for cabin temp settings (meaning you
can set it to 72* and the AC/heat will come on to keep it at 72*). It could
be a problem with the thermostat not staying constant (the AC thermostat,
not the engine thermostat).

Or, it could be an issue with the blend door not staying in the proper position
and letting the heater air come in instead of the AC air.

Scott

Interesting! I notice that when this happens i can feel the mixture of both hot and cold air blowing out of one vent. The one directly above above the stereo voume control. I am suspecting that there is a damper (for lack of a better word) that is not in the correct position.

The doors are usually controlled by vacuum lines and pots.

Could be a bad vacuum line or pot under the dashboard.

Scott

On the LS, the servos are all electric rather than vacuum and use a potentiometer for position feedback. Could be a mixing/blend servo, or possibly a sticking Dual Coolant Control Valve (DCCV) which is a pretty common issue with the LS as well.

You may want to first try resetting the climate control system which only requires pressing a sequence of buttons. I know it's been posted on this forum, try searching the forum for "DATC reset" keywords.

-Rod

I was having issues with my wife's 2002 only reliably blowing out cold when the DATC was set to 60 degrees F. If we turned the temp up as the air got too cold in the car, it may work, or it may start blowing really hot out of the vents. Last winter I replaced the DCCV to solve an issue of no heat, so I was pretty sure that wasn't the problem. Plus, I scoped the signal to the DCCV and the valves were doing exactly what they were being commanded to do, but for some reason the commands were goofy.

I checked for diagnostic codes and there were none. I also had a spare control head around so I tried it. The operation was the same.

With my scan tool I went into datastream mode and noticed that the evaporator core discharge air temp sensor was reading 255 degrees F at all times, even when the air from the vents was coming out hot. Sooo, I spent the $16.19 plus tax for a new temp sensor and it appears that all is now well.

The dealer said they've never stocked the part so evidently it isn't a common part to fail. For now though, I'm considering the repair a success.

-Rod

Makes sense. I ran the diagnostic procesure and also got no codes. The hot/cold air mixture seems to happen when doing multiple stops and starts (quick errands) like getting gas, then going to starbucks (no drive thru) etc.

I think i mentioned, in another post somewhere, a workaround.

When the cold/hot air mixture is happening on hot days:

...with the engine running (duh! had to say it)

1 hit auto and wait for full blower speed
2 turn the temp up to hot, 90 degrees. (blower speed decreases)
3 hit auto (wait a sec for blower)
4 turn the temp back down to 60
5 hit auto

quirky but it works for me.