AC Vacuum Controls

[Carl Stouffer]

My coach is a '75, so the dash air conditioning airflow is pretty dismal in the first place, but there is almost no air at all coming from the
registers at the right side of the dash. I started checking vacuum to the servos and found no vacuum at that line. Working my way back, I found I
didn't have any vacuum coming from the engine to the little round vacuum can on the firewall.

Somehow, the line had come disconnected from the intake manifold. I re-connected it, thinking that would fix everything, but it is still not working
properly. Now, when I start the engine, the recirc door closes, and the heater valve closes, but there is still no vacuum at the right side servo.
Also, when I turn on the heater, the heat control valve stays closed. It looks like all the vacuum lines are hooked up to the dash control correctly,
but things are still not operating like they should be.

Any ideas?
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

 

[bd5av8r]

Yes.
Check vacuum lines to ensure they are not blocked.
Check your vacuum mounting at the manifold to insure they are correctly
hooked up.
Is the vacuum “manifold “ at the hvac box hooked up properly and the lines
not clogged?
Check your vacuum parts on the hvac box to ensure they are free moving and
check your door linkages to ensure they work properly.
Check the cables comping from the controls to the box. Ensure they move
fully.

Sammy

On Mon, May 27, 2019 at 19:31 Carl Stouffer via Gmclist <

> My coach is a '75, so the dash air conditioning airflow is pretty dismal
> in the first place, but there is almost no air at all coming from the
> registers at the right side of the dash. I started checking vacuum to the
> servos and found no vacuum at that line. Working my way back, I found I
> didn't have any vacuum coming from the engine to the little round vacuum
> can on the firewall.
>
> Somehow, the line had come disconnected from the intake manifold. I
> re-connected it, thinking that would fix everything, but it is still not
> working
> properly. Now, when I start the engine, the recirc door closes, and the
> heater valve closes, but there is still no vacuum at the right side servo.
> Also, when I turn on the heater, the heat control valve stays closed. It
> looks like all the vacuum lines are hooked up to the dash control correctly,
> but things are still not operating like they should be.
>
> Any ideas?
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Matt Colie]

Carl,

Sammy could be right, but before you do much else, pull on the rubber connectors everywhere. I have had two of them split. They looked great, but I
could not see the split until it was stretched.

If it is a problem with the selector valve, I can't help you at all.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[jim kanomata1]

Do you have the diagram of the all vac lines.
I can send one if you do not have.

On Mon, May 27, 2019 at 8:19 PM Matt Colie via Gmclist <

> Carl,
>
> Sammy could be right, but before you do much else, pull on the rubber
> connectors everywhere. I have had two of them split. They looked great,
> but I
> could not see the split until it was stretched.
>
> If it is a problem with the selector valve, I can't help you at all.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[Carl Stouffer]

Thanks for the advice. I will check them methodically when I get some time after returning from a two week (non motorhome) trip to Alaska.

I do have the vacuum line diagrams and now, thanks to Daniel J. I have a color version.

It makes sense that some of the vacuum lines may have gotten dirt in them and might be clogged and I have repaired some of the nipples that were
split, but there may be more. I'll look closely at those things.

Thanks again.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

 

[john r. lebetski]

Use a stethoscope to trace the system starting at engine all the way through the valves to vac motors. You don't even need Ohms Law!!
--
John Lebetski
Woodstock, IL
77 Eleganza II