Climate control issue? Heater intermittent

[rmorton]

2000 SSEI with 182k miles. Engine warms up to normal temp while driving but heat hasn’t been blowing as warm as normal in the cabin. Last week I was able to get it to blow hotter by pressing the fan controls and thereby taking the climate control out of “auto” mode. In both modes, the temp was set to 90 and the passenger side was synced. Yesterday the same symptoms appeared but after an hour or so it was blowing luke warm air no matter what I did to the climate control unit. Eventually the air blowing out turned cold and nothing I did to the climate control would change the temp. The mode door is working fine - it will blow out defrost, floor and vents as commanded. Just cold. What is the best method for diagnosing this? I have a tech2 but I’m not well versed in using it. Thanks for any ideas.

[rmorton]

I’m wondering if this could be an air mix actuator going bad. Is there any way to test those? Looks like Andrew had some photos in his common problems write up but all the photos are gone now.

[Sirius]

Does the air get cold on both the passenger and driver side regardless of what the temperature is set at? There are 2 airmix actuators and it would be unlikely that both would go bad at the same time. You've probably already done this, but I'm still gonna ask, have you checked your coolant level or accomplished any maintenance on the cooling system lately?

[96 SSEi]

I would bet its the blend doors. can you increase heat and decrease heat on that side? if not, the blend door is either 'lost' or funky.

you can try the Hvac reset procedure, but I just disconnect battery for 30m and see if it can find its neutral position.
You can remove hush panel and move the door to heat position until you get it fixed

exact same issue on my 2000 - just keep moving the door...lol

[96 SSEi]

which siede is blowing cold? Is it drivers or pass or both?

[rmorton]

I will test in the morning. Pretty sure both sides are going cold at the same time. I believe I can hear a change of pitch or tone of the blower when it goes cold. It did the same thing this afternoon. Started out warm and then blew cold after about 15 minutes or so.

Yes, I keep tabs on the coolant level. Replaced radiator about 2 or 3 years ago and checked coolant before the cold set in...

[96 SSEi]

last winter I had no heat - very little on highway - turned out I had a 160 degree thermostat still in . changed it to 190 and all is good .

[rmorton]

Yesterday the heater worked as it should all day. Blew hot on both sides of the car as well as defrost etc. So I’m speculating that since the problem is intermittent, that it’s likely not a thermostat or heater core issue. Would anybody agree or am I over looking anything there? That leaves the blend doors and the climate control unit itself right?

[96 SSEi]

did you try disconnecting the battery for 30 min?

is the temp gauge reading 90 when warmed? if so, then thermostat is fine

do you have a scantool that will pull ect - that pulls directly from pcm so if the gauge is wrong - you can tell immediately

the battery disconnect will reset the head unit - give it a try, ok?