Climate Controls

[C20-67_N_MO]

Having problems with my 1995 c1500 p/k's climate controls. Seems as though all the air blows to the floor no matter what postion the selector switch is set too.

Any way to fix this or should I just bring it to a repair shop?

[75ChevyGuy]

What kind of controls do you have? Cable operated or electronic?

[JWall]

Sounds like the control panel is out.
Pretty common problem with these trucks.

[ChevyTech]

The mode doors motors should be checked first because they are a high failure part. We have talk about mode door motors in many threads and you should be able to find it with a search.

The information below is from this link about repairing the control head.
The photos in the link no longer work but I saved them long ago, and will try to attach them to the bottom of this thread


http://www.chevytalk.org/fusionbb/sh...php?tid/27558/



If you have following symptoms in your truck
1) A/C button won't work
2) Recirc won't work
3) Mode of operation knob has no effect (air comes only to floor for example)
4) Rear defog button works normally
5) Temp and fan speed knobs works normally
then you might have a similar problem I had. The fix is both easy and inexpensive. Culprit is bad transistor Q1 on your control head. By changing it (cost: 6 cents at Radioshack) everything works as usual. Here in Finland GM dealer asks 275 Eur (about same in US dollars) for the head, so there is your motivation to fix it by yourself.

To take the head off, remove dash and gently slide the head out. There are clips on both sides of the head, you need a screwdriver to tweak them slightly inwards. Disconnect all cables.

The transistor is MPSA56 (bipolar pnp) and you can locate the faulty one easily. It is the one under the bracket just next to mode of operation knob axis (NOT the easiest one at the edge of the board). Install the new one to the other side of the board, so you don't have to fit it into that extremely confined space. Make sure to connect the legs to the right holes. Emitter, base and collector are marked on the faulty transistor.

…

I didn't post at the time, but this thread helped me fix the ac controls in a 95 this time last year. My symptoms: ac compressor wouldn't engage (bypassing the low pressure switch didn't help), ac and recirculate lights didn't light up when they should have, and the blower was stuck on the floor vents - wouldn't switch to the dash or defrost vents.

Tried looking for a replacement control unit in local junkyards. Found out that the 95 part is specific to that model year. The 96 up look the same (or at least pretty darn close) on the front, but the harness connections on the back are different. The local yards wanted
around $60 for the part, but none of them had one.
…
Also, I had hard time finding an industry cross reference for the numbers listed on the transistors.
Here are the numbers
4692 (2)
4687
2857

OEM - Replacement - Radioshack

4692 - MPS2222a - 276-2009
4687 - MPS2222a - 276-2009
2857 - MPS2907 - 276-2023


Any general purpose transistor of the correct type (NPN or PNP) should work as a replacement. I had to replace one of each. I know that RadioShack carries the 2222A, but I don't think they carry the other one. Both transistors are ones I just happed to have laying around from some other project. Again, any general purpose transistor of the correct type in the same package should work.

Did this fix about a year ago, haven't had any trouble with the electronics since.

[C20-67_N_MO]

Yeah A/C works great its just the selector switch on where you want your air to go thats screwed up.

ChevyTech thanks for the write up. Sounds like I would save a TON of $$ doing it myself but I honestly do not think its the control head as you call it. Its more than likely the mode doors that direct the output air to the correct location.

[ChevyTech]

You’re welcome!

Look at the linkage and mode door motor above the gas pedal.

In the link below the photo of the dash looks to be of a 1995 style dash, and not the 1990 model of the truck the thread is about.

http://67-72chevytrucks.com/vboard/s...d.php?t=440628

[ChevyTech]

Here is the photo from the link in my post above this.

This looks to be the sytle of dash in your 1995.

The mode door motor that is above the gas pedal is the one you should look at.

[C20-67_N_MO]

So is it safe to say that your above post would still fix my problem with the mod doors?

[ChevyTech]

On this electronic system it is never safe to assume you know what the problem is.

Only when you have it fixed can you be sure.

Mode door motors are a very high failure part, but starting with the 1995 trucks the HVAC control head is a very weak point too.

I keep extra mode door motors around because there is a good chance I will need them. I hoard them. They a just a few dollars at the U-Pull-It.

[clay68c10]

I had the same problem on my 93. The linkage arm fell off its pivot right above the gas pedal. Slipped it back on last year and it still works fine. It was a beetch to get to.