Re: Suburban A/C fix + Vintage Air?
 

Rear AC Wiring Diagram

http://johnnynightstick.s3.amazonaws...86_C69_RAC.jpg

Rear window wiring diagram.

http://johnnynightstick.s3.amazonaws..._PWR_RWIND.jpg

Re: Suburban A/C fix + Vintage Air?
 

This is awesome, I also noticed your "fundamentals of air conditioning" link!
Thanks a ton for making all that available!

Re: Suburban A/C fix + Vintage Air?
 

hey hey, noticed you were a fellow east bayer, care to share you parts guy? About to start restoring my wifes 73. Also plan on rear ac.

Re: Suburban A/C fix + Vintage Air?
 

PM Sent!

Re: Suburban A/C fix + Vintage Air?
 

I'm late to this as well. But 2 things. Definitely only use AC o rings. and 2, if you do 134a be sure to get the biggest parallel flow condenser you can fit. Okay, actually 3 things. I would use a compressor that's in the 9.5+ cubic feet / revolution area. I don't know if the trailblazer accessories allow it but something like a denso 10s17F or a 10s20F. Many of the compressor you find will be sized for a single evaporator system and will likely be a bit under sized. I suggested the 2 above as they are bigger than your typical Sanden from a cubic feet per revolution standpoint.

Re: Suburban A/C fix + Vintage Air?
 

This is what I bought: https://www.summitracing.com/parts/HLY-20-142
Which comes wit an Sanden SD 7 (no real details on that page though).

I have the parts, but not installed them yet...
I can't even find details on what "cubic feet per rev" this unit puts out.

Re: Suburban A/C fix + Vintage Air?
 

SD7 is just the family of compressor. On the nameplate it should give the actual model of the compressor and you could look it up on Sanden's website. Something like a SD7H15 would be 154cc/rev and just under 9.5CI/Rev. That would be close. I know late model GM stuff uses 200cc/rev on dual evaporator orifice tube systems. I know the front system on the 73-91 Burb is an orifice tube but not sure if the rear is a TXV or orifice. I would think they would match them?

Re: Suburban A/C fix + Vintage Air?
 

I just looked at one of the review's on summit racing from the link you sent me, they put a picture of it mocked up on their Camaro. Name plate read SD7B10. Unfortunately that's a 100cc/rev compressor. My opinion, way too small for what you're trying to accomplish. Do you know if the Trailblazer SS is the same offset crank pulley as a standard truck drive?

http://www.sanden.com/pistoncompressors.html

Re: Suburban A/C fix + Vintage Air?
 

Nice!

Re: Suburban A/C fix + Vintage Air?
 

I am in the middle of putting the vintage air in my dash and if it will not cool the Burb off I will be retrofitt a rear air, already grabbed all the parts from a doner... lots of good info on this post! Thanks

Re: Suburban A/C fix + Vintage Air?
 

Ok, it's been a year! Crikey!

I just reached out to Sanden to see of the compressor I have is indeed undersized. No point in installing it, if it's too small!

I'm going to lay this out this week and get crack-a-lackin' on this project.

PS: I asked my local mechanic if he would be interested in doing some of the work. He said two things to me:
1. You're a lot braver than I am!
2. This sounds expensive!

The recent heat wave, and the upcoming July 4th weekend are lighting a fire unner me.
Here we go!

Re: Suburban A/C fix + Vintage Air?
 

Honestly, none of this stuff is super high tech. You just need to match the right parts. Definitely call Vintage Air if you have questions about parts selections, they're currently helping me out on my own dual ac unit in my Blazer. Only difference is I'm mounting my second evaporator in my center console so the passengers get cool air on their face and not the back of their shoulders and top of their head.

Re: Suburban A/C fix + Vintage Air?
 

I also had mentioned getting the biggest parallel flow condenser you can fit. That's a must. Also do not get anything thinner than a 1" for dual air. Vintage air has some but Restomod air has a bunch of different sizes too.

Re: Suburban A/C fix + Vintage Air?
 

Here is what I have:
https://www.rockauto.com/en/moreinfo...=1295591&jsn=1

Construction 6mm
Core Depth (in) 7/8
Core Height (in) 16-1/4
Core Length (in) 28-7/8
Inlet Type # 8 Male O Ring
Outlet Type # 6 Female O Ring

Re: Suburban A/C fix + Vintage Air?
 

The original engine in your truck was dressed with a Frigidaire Harrison A6. I'd try to come close to the specs on that beast for dual evaporators.

The Harrison A6 compressor was a nearly indestructible beast. It will push out 27,000 BTUs at 2,000 rpm and as high as 42,000 BTUs at 4,000 rpm with a discharge rate of 240 p.s.i. That’s enough cold air to cool a small house (my window-mounted air conditioners are only rated at 5,000 and 8,000 BTUs).
They don't care whether you turn em clockwise or counterclockwise they'll work in either direction.
Not fuel efficient at all but they moved so much refrigerant around that it would freeze you out of the passenger cabin when the system was properly charged.

The compressor that GM put in the 3/4ton suburban with the 6.0L and dual air using Envirosafe refrigerant may get you close to the performance of the A6 with R12.
Be aware that Envirosafe is a hydrocarbon blend refrigerant. For those that can't help but mention that hydrocarbon refrigerants burn... R134a & R12 burn too. The byproducts of automotive refrigerant combustion are really nasty. Hydrocarbons don't generate Phosgene or Carbonyl Fluoride gases when they burn. I choose to not melt my lungs and brain.

Re: Suburban A/C fix + Vintage Air?
 

Anyone have a picture of the underside of a Suburban? I'm trying to figure out where these hard lines route!

https://photos.smugmug.com/VehiclesO...IMG_7394-M.jpg

Re: Suburban A/C fix + Vintage Air?
 

Made some progress today. Got the rear unit cleaned up and installed, ran the hard lines under the truck, and some odds and ends.

https://photos.smugmug.com/VehiclesO...IMG_7395-M.jpg

https://photos.smugmug.com/VehiclesO...IMG_7399-M.jpg

Old sensor:
https://photos.smugmug.com/VehiclesO...IMG_7402-M.jpg

Expansion valves:
https://photos.smugmug.com/VehiclesO...IMG_7405-M.jpg

https://photos.smugmug.com/VehiclesO...IMG_7406-M.jpg

Sensor was different on the new unit, so....
https://photos.smugmug.com/VehiclesO...IMG_7407-M.jpg

https://photos.smugmug.com/VehiclesO...IMG_7408-M.jpg

Hanging proud:
https://photos.smugmug.com/VehiclesO...IMG_7410-M.jpg


Manifold:
https://photos.smugmug.com/VehiclesO...IMG_7412-M.jpg

https://photos.smugmug.com/VehiclesO...IMG_7414-M.jpg

Figgered out how to run the hard lines a little bit (thanks to my 10 year old's son's help! LOL)
https://photos.smugmug.com/VehiclesO...IMG_7416-M.jpg

Old Unit:
https://photos.smugmug.com/VehiclesO...IMG_7423-M.jpg

https://photos.smugmug.com/VehiclesO...IMG_7424-M.jpg


Next up to figure out the switches and stuff:
https://photos.smugmug.com/VehiclesO...IMG_7426-M.jpg

https://photos.smugmug.com/VehiclesO...IMG_7427-M.jpg

Re: Suburban A/C fix + Vintage Air?
 

And then I cracked a cold one...

Re: Suburban A/C fix + Vintage Air?
 

Looks like you have a compressor cycling thermal cutoff switch with a capillary tube in the Evaporator. There should be a Low pressure cutoff switch on the accumulator as well. The aftermarket compressor and or hoses likely has provision for a high pressure cutout switch. If you're running R134a you'll want to add a HPCO switch in series with the LPCO and thermal switches because it has a tendency to run much higher pressures than R12 or HC blends.
I'd use a relay to offload the control amperage to the actual compressor clutch so the high amp load of engaging the electromagnet is run through an easy to replace $1.25 relay rather than the HVAC controls and the LPCO and Thermal switches.

Get a relay socket rather than using 1/4" disconnects. It makes the wiring job look better and it's much easier to replace the relay when and if it needs to be done.
Run a ground in series through the LPCO, HPCO, and Thermal switch to terminal 85 of a Mini ISO Bosch Automotive relay.
Run the Green AC compressor "on" wire from the HVAC control panel to terminal 86 of the same relay.
Run a 14ga wire through a 16ga fusible link or a 20A ATC fuse from the J stud on the firewall to the relay common terminal 30.
Run a 14ga wire from relay terminal 87 (normally open) to the actual compressor clutch plug.

Re: Suburban A/C fix + Vintage Air?
 

I plan on calling these guys and restomod air for some tips, and I might end up making my own lines.

What unit did you go with for the rear?

Re: Suburban A/C fix + Vintage Air?
 

Here’s what I learned/tl;dr, which is going to sound obvious, and phillipm was totally right:

• Select the compressor suited for your application.
• Select the bracket to locate the compressor.
• Make sure your compressor pulley groves/belt ribs match your engine (mine is 6).
• Pulley Offset (mine is Truck)
• Once you know where you compressor is to be monted, you can map out your lines.

Spent half the day on the phone and doing some research.
I called Restomod Air (condenser) and Vintage Air (compressor),
and ended up with “Classic Auto Air”(recommended by Restomod Air) which seems to be the best suited to getting your stock stuff working again.

Taking @phillipm advice, I’m going to upsize the Condenser, plus get parallel flow.
I verified that the stock size of the Suburban's (’76) condenser is:

Depth: 7/8”
Height: 16 1/4"
Width: 28 7/8"
Inlet: #8 Male
Outlet: #6 Female

“Classic Auto Air” suggested the

16x27” Condenser
in: #8 male
out: #6 male

Notice how the OEM has M/F in/out?

This is the issue with trying to piece things together and mix and match parts.
I was hoping I could order hoses, and just bolt this thing together, but that was a bit of a pipe dream.
The good news is that “Classic Auto Air” has all the fittings and the guy assured me that we can just create custom lines where needed (under the hood). He said he’s familiar with the stock components, so putting together a list of parts should be easy.

The compressor piece of this had me pulling out my hair. I don’t know why it’s so hard to find details/specs on the different models.
First I emailed Sanden and asked for a recommendation. I was glad to get response, which said essentially:

the SD7B10 is probably too small, and he suggested a SD7H15, but said they have over 1,000 models and told me to call one of the distributors.
So I called Vintage Air, who also were cool and answered my questions.
Josh took the time to look up numbers and parts and suggested 04709-vma (5.5 CI w/V-belt) (this is actually 7 groove belt and won’t work, but the size seemed good).

http://www.sanden.com/productlibrary...uide_Rev_2.pdf
For Sanden, you can break down the model like this SD7B10:

SD (wobble plate type)
7 (# of pistons)
B (port location B-Body or H-Head)
10 (@9,000 rpm displacement in cc’s multiplied by 10, so: 100cc)

So then the SD7H15 is 150cc (9.3 Cubic Inches)

Mike at “Classic Auto Air” confirmed what was recommended on this thread, but he said “stay away from 7176” because it would be too small. Yep, its the SD7B10 (that I already bought). Sigh.

They can put the whole thing together, bracket, compressor, condenser, accumulator, lines, and fittings. Everything
but a new drive belt, it seems. So that’s likely what I’m going to do.

I also researched the Denso compressors and confirmed that the 10S20F is used on 2008 (my LS engine year, I think) suburbans with rear air. So, breaking this one down, it’s a 10 Piston, 200cc unit. But I think it uses the ’stock manifold’.

Mike had some opinions on what compressor he would recommend (Sanden 514) I think… but that’s a bit small sounding (on paper)

The Burb used an orifice tube in front (’76) and a Thermal Expansion Valve in the rear unit.
See pics above for replacing the TXV.

So, it looks like I'm not getting AC for the 4th of July break after all!

Re: Suburban A/C fix + Vintage Air?
 

I have a German unit called a Siroco. Its small and I have made quite a few modifications to it. Once I have it up and running I will post results and photos of it! Probably take most of the summer at the rate I'm finding time to work. Haha

Re: Suburban A/C fix + Vintage Air?
 

Glad you made those calls! Another unit you should look at would be a Denso 10S17F. I've used it and it has plenty of capacity for what you're trying to do. Might be the easiest way to go if you have factory brackets. I've used the Alan Grove low mount Sanden bracket on my Square Body and it worked, but it was tighter than the factory bracket and compressor.

By the way the Denso compressors can be replaced from the factory manifold to some regular O-Ring fittings. Check out coldhose.com or Vintage Air for those.

Re: Suburban A/C fix + Vintage Air?
 

It's hard to believe that TWO YEARS have gone by since I started this project, but we all know that can happen.
Seems that about every spring I start getting the AC itch.

The good news is that I just put in my order for all the parts at "Original Air".

I bought before I did my research and am going to sell some of the stuff I got originally. Live and learn.
This time I called the guy from OA and he helped me piece together a kit. He suggested running all new hoses to the rear.

Will the Covid thing, they are shipping slowly, but I should be getting something in a couple of weeks.
I think the "install" part should go fast. And "getting it working" might be a different challenge!

I'll need a crimper, and a way to figure out how to trigger the electric fans with the AC comes on. I'm running an MSD LS box...

I wanted to thank everyone who posted here, it really helped me get my head around this project so far.
I'm still an AC noob. That's about to change right quick though.

Re: Suburban A/C fix + Vintage Air?
 

I'm betting this experience has schooled you well so it's possible you're beyond your self pro-claimed 'noob' rank. :lol: