LMC AC controller has too many detents

[Chris64]

I ordered the AC/heater controller to replace the one I have (which is missing knobs, scratched and just looks awful).

The problem is it has too many detents for the top lever. The label is correct, it has 6 sections, but 7 detents.

I'll try to get fancy with fonts to explain - When I slide the knob it snaps on too many places:

Stock
OFF A/C VENT HEATER BI-LEVEL DEF
X X X X X X

LMC Controller
OFF A/C VENT HEATER BI-LEVEL DEF
X X X X X X X

So that's weird, right? I'm not sure if this is going to work properly. I can just aim for the middle and ignore the detent, or I can probably use parts from this to make the factory one look new again. I'm just wondering if this is a defect or maybe not a big deal. I could even possibly modify it to have the proper detents.

On a side note: I always hated this control mechanism. Even in the 80's. Japanese cars AC controllers have always made way more sense to me. What if I want the recycle on/off with floor vent with heater on with AC on? Just because!

 

[ali_c20]

I have an original AC controller in my 79 K5 and I think there is a detent between vent and heat. Not 100% sure, I will check and report.

 

[legopnuematic]

1973-1975 HVAC control:

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1976-77

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Later is similar to 76-77 but minor changes.

 

[1lejohn]

I think the bottom one is for a later model truck. 80's version. It matters on the vacuum switch where all the lines come in that run to the plenum doors.

 

[Chris64]

This is what I have

You must be registered for see images attach

So six positions. The stock one for sure only detents on those 6 positions. The LMC just has this exact same graphic, but with 7 detents.

 

[Jgonick]

The stock one for sure only detents on those 6 positions. The LMC just has this exact same graphic, but with 7 detents.

Surely they didn’t put the graphic (front) on a wrong switch- but I guess anything is possible.

My suggestion is to call LMC and ask. I’ve had to call them in the past to clarify a description on a certain part. They were very helpful when I called.

 

[Chris64]

Surely they didn’t put the graphic (front) on a wrong switch- but I guess anything is possible.

My suggestion is to call LMC and ask. I’ve had to call them in the past to clarify a description on a certain part. They were very helpful when I called.

You know - I didn't even consider this because most online places don't give any service. I called them and they were very helpful. They wanted pics so they could forward them to the right people and if it's wrong they'll replace it.
I'll keep this thread updated with the outcome but bravo LMC for having humans to help.

 

[75gmck25]

The dash controller has to match the large vacuum switch bolted on the back (it’s visible in the photo of the newer switch). You cannot mix and match years.
Also, my original ‘75 controls do not have the extra detent you show in your diagram.

The ‘75 switch has no Max position because recirculate is controlled by the Temp slider. There is a temperature slider detent just short of full cold, and that is normal mode. Then you push the temp slider all the way to the left and it hits the Max/recirculate detent and you will see the kick panel recirculate vent open up.

My recirculate mode is a little slow to kick in, like it doesn’t quite apply enough vacuum to the recirculate pod, but it does slowly move after about 20-30 seconds.

 

[Chris64]

The dash controller has to march the large vacuum switch bolted on the back (it’s visible in the photo of the newer switch). You cannot mix and match years.
Also, my original ‘75 controls do not have the extra detent you show in your diagram.

The ‘75 switch has no Max position because recirculate is controlled by the Temp slider. There is a temperature slider detent just short of full cold, and that is normal mode. Then you push the temp slider all the way to the left and it hits the Max/recirculate detent and you will see the kick panel recirculate vent open up.

My recirculate mode is a little slow to kick in, like it doesn’t quite apply enough vacuum to the recirculate pod, but it does slowly move after about 20-30 seconds.

That's good info - thank you. I was wondering about that left detent on the cold. Now I know.

 

[85 red GMC]

1973-1975 HVAC control:

You must be registered for see images attach

1976-77

You must be registered for see images attach

Later is similar to 76-77 but minor changes.

I was thinking bi-level which came along later in the offerings. If you don't have the right vacuum set up for the connection, I would think the extra space would cause problems with vacuum distribution. Can they send you one for the right vehicle you have and take this one back?

 

[85 red GMC]

My 1985 has the bi-level I believe.