Thread: HVAC Mode Selector , A/C Light and Blend Actuator

I only drove my son's 2003 GTP once on the day we got it. Today I get in it to run a quick errand and the mode selector knob on the HVAC control breaks off in my hand. Naturally it's my fault that it's broken now.

So I have questions. The mode selector shaft did not want to turn, hence the broken knob. The knob had also clearly been glued back together in the past so that doesn't help the situation. So first question is whether it's common to have the mode selector button seize up. I squirted a bit of WD40 in there and operated it with pliers. It seems to be okay now. Those HVAC controls are expensive! I ordered a used knob on eBay that appears to be in tact. The Dorman knobs evidently aren't the right color based on the reviews, and they send you 3 knobs when only one actually fits.

Second question: The A/C light is always lit. If you push and hold the button, the light goes out and the compressor shuts off but as soon as you release it it comes back on. I guess I don't care if the compressor is always running - I never mess with that button anyway. I would think, however, it should shut off the A/C and wonder if it's a symptom of a bigger problem.

Last, the left side air blend actuator does not appear to be working properly. A/C on the right side is ice cold while it's luke warm on the left side. There is some range of operation - I can adjust it from lukewarm to hot, but it never gets cold. Is this a sign the actuator motor is going bad? Or can it be recalibrated?

03 is a strange year in general, but I believe the ac is the same as 97-02. I would look at replacing the whole hvac control as it can cause all those symptoms and go from there.

I think if you disconnect both battery terminals and touch them together for two minutes then replace and put the key in the on position it "re-calibrates" them

Originally Posted by Bronco Boy

I have a Dorman knob. Can you tell the difference?


Hint. You can't tell the difference.

So I guess you can't believe everything you read on the Internet? Shocker!

Hopefully the used, factory one will be just as nice.

I like what you did with your radio filler, too!

Okay I fixed it today. It's a bad news, bad news, good news story.

Bad news is that after removing the old blend door actuator and manually rotating the door all the way to cool, it was still warm on the driver's side.

The other bad news is that the $20 replacement actuator motor I got directly from China was wrong anyway. Pins were different. I plugged it in anyway and it did nothing.

Good news is that the real problem was that it was low on refrigerant. Apparently the A/C system overcomes quite a bit of warm air that gets mixed into the air stream. It was 90 degrees out today and the passenger side was cool but not cold. On a hunch I hooked the gauges up to it. Pressures were low and there was evidence of ultraviolet leak detector in the system. It took 12 oz of r134a (all I had) and the pressures are close to where they should be. NOW the A/C is COLD cold on both driver and passenger side. I think the leak is the high pressure port which will suck to replace. I'll have to monitor it and see how quickly it leaks down.

Originally Posted by turbojimmy

Okay I fixed it today. It's a bad news, bad news, good news story.

Bad news is that after removing the old blend door actuator and manually rotating the door all the way to cool, it was still warm on the driver's side.

The other bad news is that the $20 replacement actuator motor I got directly from China was wrong anyway. Pins were different. I plugged it in anyway and it did nothing.

Good news is that the real problem was that it was low on refrigerant. Apparently the A/C system overcomes quite a bit of warm air that gets mixed into the air stream. It was 90 degrees out today and the passenger side was cool but not cold. On a hunch I hooked the gauges up to it. Pressures were low and there was evidence of ultraviolet leak detector in the system. It took 12 oz of r134a (all I had) and the pressures are close to where they should be. NOW the A/C is COLD cold on both driver and passenger side. I think the leak is the high pressure port which will suck to replace. I'll have to monitor it and see how quickly it leaks down.

Definitely get that leak fixed asap. running the system like that could destroy your compressor or worse. I'm lazy, so I always inject some uv dye into the system to find the leak quick. Everything other than the dye and refrigerant you can rent at autozone. It's really easy. If the leak is the connector, it's almost 99% always the schrader valve which is easy and cheap to replace. Just make sure you vacuum the system for an hour, let it sit and watch the gauges to see if the leak is gone, then charge the system (don't charge on high side) and enjoy!

Yes it is the Schrader valve that's leaking. I wonder if it's my gauge kit that's doing something to them. It's a new kit that I've only used twice and both times I wound up with leaking Schrader valves. First time was the low side valve on our Jeep and now the high side on the Pontiac. Neither were leaking when I started. I had vacuumed the Jeep down and it held the vacuum overnight until I recharged it. But then after charging the low side valve leaked. The cap stopped it, but they're not designed for that I don't think (though they do have o-rings in them so they're more than just a dust cover). I checked on it a few days later by removing the cap and it had stopped. Hopefully the same will happen to the GTP.

I found out the hard way that screwing them all the way down can cause leaks. However, I've started just always replacing them since they're dirt cheap and haven't had issues since. And you're right, it'll hold for a time but you shouldn't rely on the cap since it's not designed for full pressure. More likely is that the o- ring in the valve is just old and needs replacing though. Good luck!