Jeep TJ A/C Control Head

G

Greg C.

Active member
Oct 11, 2019
256
23
28
Today I finished the rough installation of the all the wiring and vacuum lines from the new Jeep control head to the GMC. I had labeled all wires in
the dash and on the control, and cut the GM plugs off the wiring going to the stock HVAC panel and used male/female connectors to hook up the Jeep
panel.
The Jeep head uses vacuum lines that are the same size in diameter as the GMC. Not knowing how else to connect them, I drilled .250 aluminum rod with
a .136 number drill and made female to female adapters. I carefully coated the vacuum lines with RTV, avoiding the ends to prevent clogs, and slid the
GMC lines into one end and the Jeep lines into the other. The lines fit snugly into the adapters, but I wanted to minimize leaks, so I glued them in.
The Jeep control came with a vacuum pigtail, and I got the chassis end of the pigtail from a wrecked TJ. This way the vacuum lines can still be
separated at the pigtail plug.
Once done, I fired up the engine for a vacuum source and began testing the vacuum operation. Everything seems to work pretty good. A turn of the knob,
and different modes were selected and the various air doors operated as they should.
I used a blend door actuator from the Jeep on the old cable push pull temp door. It works great. You can turn the temp knob from blue to red and watch
the temp door cycle up and down.
I uploaded some pictures on the photo site, here: http://www.gmcmhphotos.com/photos/g7367-interior.html

I tried uploading a video of everything working, but was unable to do so. That's unfortunate, because you can really see the air doors moving in
response to the mode knob.

Also, the blower fan DOES NOT run on low all the time now, if the Jeep control ( guess it's now a GMC control, or just A/C control) is turned OFF.
This shuts off the blower fan completely. Also, the Jeep control head has built in lighting which I connected to the coach. It will dim with the rest
of the instrument lighting.

I need to tweak the defrost door actuator a little bit, but overall, I am very happy with the outcome.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
 
Great job!
--
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid
November 2015.
 
I just wanted to report that the new Jeep control head works perfectly with the GMC a/c system. I now have Fan OFF, LOW, MED, and HIGH speeds. The
Temperature control moves the blend door from fully open (cold) to fully closed (hot), and anywhere in between. The mode switch energizes the
compressor at RECIRC, A/C, DEFROST/HEAT and DEFROST. The defrost door, formerly held shut by a spring, is now held shut by vacuum except for
DEFROST/HEAT and DEFROST. In the event of loss of vacuum, the system now defaults to DEFROST instead of DASH AIR. The dash air flap, heat flap, and
recirculating flaps all move into position as they should, with NO VACUUM LEAKS! In DEFROST/HEAT mode, the heat door and the defrost door both open to
about half way.

To make this work, I removed the spring from the defrost door, and modified the defrost vacuum actuator to be normally open, and close when vacuum is
applied. I have since been told that there are vacuum solenoids available that can use a lack of vacuum signal to apply vacuum to another port. This
would have enabled me to do the same thing without modifying the vacuum actuator bracket, so that's an option for someone else if they go this route.

I also removed the spring from the dash air door, which held it open at all times until vacuum was applied. I reversed the action of the dash air
actuator as well so that is now closed by the vacuum signal from the Jeep head. The Jeep head applies vacuum to almost every line in every position,
EXCEPT in defrost. That is so that the Jeep defaults to defrost in the event of vacuum loss. Safety reasons I assume. My coach was dash air flap open
in the default situation, and I never had anything in the vacuum system to work until now.

Anyway, I was tickled to death with the final results, so I had to share. So now I am finishing up wiring the new gauges and ready to start on my
fiberglass A/C ducts. The defrost ducts are done except for cutting 6 holes in them to receive the moveable registers, so that has to be done as
well.

I am moving some more pictures to the photo site.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
 
Have all this in pictures and parts list by chance? Like to modify my 1974.

Randy Hecht
Roswell, GA

1974 Canyon Lands GMC Motor-coach

>
> I just wanted to report that the new Jeep control head works perfectly with the GMC a/c system. I now have Fan OFF, LOW, MED, and HIGH speeds. The
> Temperature control moves the blend door from fully open (cold) to fully closed (hot), and anywhere in between. The mode switch energizes the
> compressor at RECIRC, A/C, DEFROST/HEAT and DEFROST. The defrost door, formerly held shut by a spring, is now held shut by vacuum except for
> DEFROST/HEAT and DEFROST. In the event of loss of vacuum, the system now defaults to DEFROST instead of DASH AIR. The dash air flap, heat flap, and
> recirculating flaps all move into position as they should, with NO VACUUM LEAKS! In DEFROST/HEAT mode, the heat door and the defrost door both open to
> about half way.
>
> To make this work, I removed the spring from the defrost door, and modified the defrost vacuum actuator to be normally open, and close when vacuum is
> applied. I have since been told that there are vacuum solenoids available that can use a lack of vacuum signal to apply vacuum to another port. This
> would have enabled me to do the same thing without modifying the vacuum actuator bracket, so that's an option for someone else if they go this route.
>
> I also removed the spring from the dash air door, which held it open at all times until vacuum was applied. I reversed the action of the dash air
> actuator as well so that is now closed by the vacuum signal from the Jeep head. The Jeep head applies vacuum to almost every line in every position,
> EXCEPT in defrost. That is so that the Jeep defaults to defrost in the event of vacuum loss. Safety reasons I assume. My coach was dash air flap open
> in the default situation, and I never had anything in the vacuum system to work until now.
>
> Anyway, I was tickled to death with the final results, so I had to share. So now I am finishing up wiring the new gauges and ready to start on my
> fiberglass A/C ducts. The defrost ducts are done except for cutting 6 holes in them to receive the moveable registers, so that has to be done as
> well.
>
> I am moving some more pictures to the photo site.
> --
> Greg Crawford
> KM4ZCR
> Knoxville, TN
>
> "Ruby Sue"
> 1977 Royale
> Rear Bath
> 403 Engine
> American Eagle Wheels
> Early Version Alex Sirum Quad bags
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
I have pictures on the photo site. Parts list is pretty basic. New or used 98-2005 Jeep TJ control head, wiring harnesses, and blend door actuator.
The rest of the parts are made on my lathe or mill.I built a new dash, you would need to enlarge the hole on the stock dash.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
 
Thanks, that works

Randy Hecht
Roswell, GA

1974 Canyon Lands GMC Motor-coach

>
> I have pictures on the photo site. Parts list is pretty basic. New or used 98-2005 Jeep TJ control head, wiring harnesses, and blend door actuator.
> The rest of the parts are made on my lathe or mill.I built a new dash, you would need to enlarge the hole on the stock dash.
> --
> Greg Crawford
> KM4ZCR
> Knoxville, TN
>
> "Ruby Sue"
> 1977 Royale
> Rear Bath
> 403 Engine
> American Eagle Wheels
> Early Version Alex Sirum Quad bags
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
You should build a kit with instructions and parts list. The factory
controls are worn out and clunky if not. Sell it.

Sully
Bellevue wa

On Fri, Aug 20, 2021 at 4:11 PM Greg Crawford
wrote:

> I have pictures on the photo site. Parts list is pretty basic. New or used
> 98-2005 Jeep TJ control head, wiring harnesses, and blend door actuator.
> The rest of the parts are made on my lathe or mill.I built a new dash, you
> would need to enlarge the hole on the stock dash.
> --
> Greg Crawford
> KM4ZCR
> Knoxville, TN
>
> "Ruby Sue"
> 1977 Royale
> Rear Bath
> 403 Engine
> American Eagle Wheels
> Early Version Alex Sirum Quad bags
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
Direct link to Greg's photo albums

http://www.gmcmhphotos.com/photos/u42866-gregc.html

-----Original Message-----
From: Greg Crawford [mailto:captgregcrawford]
Sent: Friday, August 20, 2021 6:12 PM
Subject: [GMCnet] Re: Jeep TJ A/C Control Head

I have pictures on the photo site. Parts list is pretty basic. New or used
98-2005 Jeep TJ control head, wiring harnesses, and blend door actuator.
The rest of the parts are made on my lathe or mill.I built a new dash, you
would need to enlarge the hole on the stock dash.
 
I would not be averse to writing up a how-to, if there is sufficient interest. I also still have my factory dash, so I could see if it could be
modified easily to fit the Jeep control head.

Some Chrysler products of similar years may be smaller, or not as wide. They would be even better for this, but I have not researched enough to know.
I was familiar with the Jeep TJ head, and used it.

If you get into later years, the control heads on most vehicles are incorporated into the on board computer design, and can't be used standalone.

The parts I had to fabricate were the defrost actuator bracket and bell crank, the blend door actuator adapter that fits over the factory hot/cold
door lever, the bracket that holds the blend door actuator, and

the dash air flap pivot hinge pin and attaching brackets.

It's not technically difficult, just time consuming.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
 
So I was out at the coach today, measuring my foam and trimming it for laying up the passenger side ductwork. Driver side ductwork fiberglass is now
complete.

I looked down at the air box, and noticed that the dash air flap was open. Since the system now defaults to defrost, I was a little concerned that
something was wrong. Then I looked at the mode switch.

It was in A/C mode. Yep, three days after the engine was ran last for testing, the system IS STILL HOLDING VACUUM! I switched it to OFF, and the dash
air flap slowly closed.

I am overjoyed!

I can tell from lack of responses to this thread that there is not a lot of interest in this project, but I was so excited I had to share. Feel free
not to read! Oh, and by looking at the factory dash parts, I

believe that anyone could replace the factory A/C head with the Jeep head with just a little cutting/filing on the steel backing plate and plastic
dash bezel. It's slightly larger than stock.

If a vacuum solenoid that actuates with a lack of vacuum signal to a sensing port is available, this would eliminate the hardest part of my
modifications. Someone had mentioned that this is possible.

If that is the case, then total disassembly of the dash would not be necessary to do this mod.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
 
> I can tell from lack of responses to this thread that there is not a lot of interest in this project, but I was so excited I had to share. Feel
> free not to read!

Au contraire!... This is a great upgrade and a true solution for the disappearing vacuum disks in the OEM controls. I think a kit or a step-by-step
photo essay would be a big hit! If there was a way to preclude modifying the OEM opening that would be even better. I have a '76 that uses the recirc
damper actuator reconfigured as the 'max air' damper - it bypasses the heating coil and directs all the air through the cooling coil - so that may
affect how the system is arranged.
--
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid
November 2015.
 
Don’t underestimate the interest or the utility in this mod. It’s really cool and has potential

Sent from Mailhttps://go.microsoft.com/fwlink/?LinkId=550986 for Windows

From: Greg Crawford
Sent: Monday, August 30, 2021 7:41 PM
To: gmclist
Subject: [GMCnet] Re: Jeep TJ A/C Control Head

So I was out at the coach today, measuring my foam and trimming it for laying up the passenger side ductwork. Driver side ductwork fiberglass is now
complete.

I looked down at the air box, and noticed that the dash air flap was open. Since the system now defaults to defrost, I was a little concerned that
something was wrong. Then I looked at the mode switch.

It was in A/C mode. Yep, three days after the engine was ran last for testing, the system IS STILL HOLDING VACUUM! I switched it to OFF, and the dash
air flap slowly closed.

I am overjoyed!

I can tell from lack of responses to this thread that there is not a lot of interest in this project, but I was so excited I had to share. Feel free
not to read! Oh, and by looking at the factory dash parts, I

believe that anyone could replace the factory A/C head with the Jeep head with just a little cutting/filing on the steel backing plate and plastic
dash bezel. It's slightly larger than stock.

If a vacuum solenoid that actuates with a lack of vacuum signal to a sensing port is available, this would eliminate the hardest part of my
modifications. Someone had mentioned that this is possible.

If that is the case, then total disassembly of the dash would not be necessary to do this mod.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
 
Greg -

I am completely interested in this mod and plan to do it as soon as you post the details.

I've purchased - but not yet installed - the "air horn" modification for my 1973 completely stock system. As preparation for that modification - I
thought it might be wise to asses the system before ripping into it. I emptied, vacuumed, and recharged with Duracool and was pleasantly surprised to
get cold air blowing. now... I'd like to get more air blowing. :)

Thanks for your contribution to our GMC Motorhome community !!

Steve W
1973 23 Yellow
southern California

--
Steve W
1973 : 23'
Southern California
 
I am interested in how you accomplished this. I’d like to do the same to my 74.

Randy Hecht
Roswell, GA

1974 Canyon Lands GMC Motor-coach

>
> Greg -
>
> I am completely interested in this mod and plan to do it as soon as you post the details.
>
> I've purchased - but not yet installed - the "air horn" modification for my 1973 completely stock system. As preparation for that modification - I
> thought it might be wise to asses the system before ripping into it. I emptied, vacuumed, and recharged with Duracool and was pleasantly surprised to
> get cold air blowing. now... I'd like to get more air blowing. :)
>
> Thanks for your contribution to our GMC Motorhome community !!
>
> Steve W
> 1973 23 Yellow
> southern California
>
> --
> Steve W
> 1973 : 23'
> Southern California
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
Greg,
Please don't use active responses here to determine value of your post! Between current interest that the reader may need a free day to tinker and
figure out current status (like me) and future interest of the searchable forum...posting stuff you find can work is great! As they age, we need more
options, and twenty people might need it next year!? Who knows...

Inspired by your first post, I went out and stuck an inspection cam up every port and access on my 1975 to see what of mine is working and what is
not. There is a strange combination of which vents and intakes, but now I have it recorded.

I know for a fact my 78 hvac control needs a new head, or at least the hard to come by wheel thing. PO left the dash cover off for years in nearly
full sun. that little control wheel for the vacuum just crumbled. May end up with your Jeep solution. So count me in as one who might use every scrap
of info you post about! Thanks

--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
 
I second (third?) Tyler’s response. The mechanical AC/HEATER controller was
my biggest head scratcher when contemplating my custom dash several years
ago. This Jeep controller will become more and more relevant as time
passes. Since you have already done the fieldwork and trial and error you
might want to take the time to document the journey.

Sully
Bellevue wa

> Greg,
> Please don't use active responses here to determine value of your post!
> Between current interest that the reader may need a free day to tinker and
> figure out current status (like me) and future interest of the searchable
> forum...posting stuff you find can work is great! As they age, we need more
> options, and twenty people might need it next year!? Who knows...
>
> Inspired by your first post, I went out and stuck an inspection cam up
> every port and access on my 1975 to see what of mine is working and what is
> not. There is a strange combination of which vents and intakes, but now I
> have it recorded.
>
> I know for a fact my 78 hvac control needs a new head, or at least the
> hard to come by wheel thing. PO left the dash cover off for years in nearly
> full sun. that little control wheel for the vacuum just crumbled. May end
> up with your Jeep solution. So count me in as one who might use every scrap
> of info you post about! Thanks
>
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
You might want to consider making a kit to sell.
I'd be interested.
--
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
 
Thanks, all, for the responses. I do plan on documenting everything better on the photo site, but it is difficult for me to use. I can only download
two pictures at a time, otherwise, you think you have successfully uploaded to the site, only to find out that you have not.

It's probably more user error than anything. I may have to put together a slideshow presentation or something.

I wasn't ready to start this project when I did. It just worked out that way because one thing led to another. I'm trying to get it all buttoned up
for some camping trips this month, and then I'll know how well everything is working.

I discovered my start battery is bad (2016 vintage) and I've lost the freon charge while working on the timing chain and A/C project, so I have to
address those as well.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
 
That sounds like the new hot set-up! I would definitely be interested in doing this or something similar in the future, as required, to make my dash
air/heat/defrost system continue to work.

It sounds a little complicated, but once I would see it in pictures and instructions, it probably won't be that hard to execute.

Thanks for experimenting with this and sharing your successful results. Very encouraging!
--
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
 
I am very interested in this too, as my 9 port valve (made of unobtanium) is leaky and unreliable.
This looks like a solution that would be more reliable and extend parts availability.

John Shutzbaugh
--
John Shutzbaugh, Vacaville, CA, ncserv;
78 Buskirk stretch, "What were we thinking?"
 
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