The Stovebolt Site Forums The Shop Area The HiPo Shop A/C question for Koolkar or anyone else?

A friend of mine is putting air conditioning into a restored '71 Dodge school bus (mini size, based on D-300 chassis).

He is using a new aftermarket underdash unit in the front, and I scored a free used rear unit from a Suburban. I cut the hoses in the rubber section, but we're trying to figure out how to make new hoses and adapt them to the existing aluminum tubing on the Suburban unit.

Also, any ideas on his compressor mounting problem?

Here's his quote to me:
" I've got both fan/coil units mounted and wired and the conduit in
place between the rear overhead and underfloor and the conduit running
along the frame. The condenser was too wide to fit with the fittings,
so I've ordered another that's 4" narrower. I've got the t connectors
ordered but haven't yet addressed how to physically attach the
refrigerant lines to the rear unit. I'm wondering if I can lightly
score the aluminum tubing with a tubing cutter then put it into the
rubber lines with multiple clamps on it. Or, maybe I can machine a
brass adapter and mount the adapter to the scored line with JB Weld?
What are your suggestions, Bill? It looks like I'm going to have to
modify or make a compressor adapter. I need to come up with a
compressor mount from an existing 318 then weld new mounts to it. "

Any help will be greatly appreciated!

Thanks,

---> Bill

I just read a artical on installing air. They cut the fittings off and rotated them for something or the other and had them TIG welded back together. This could be a option if you only have a few to do. If you are going to run R134, the high side could reach as much as 300psi on a hot day. You would really have to clamp them well to hold that type of pressure. The aluminum splice you can by has sharp teeth so the hose can't come off. You might try a AC supply house or big truck dealer/shop for fittings. You might find something that would work. Our school bus shop would by from the local Kenworth dealer. They were a Carrier dealer. Some of the local Carquest and NAPA auto parts also sold fittings.

At the parts store, we used to a sell an A/C compression fitting with a hose barb on the opposite end (made by Murray). Sounds like what you need and should be readily available at a good parts store.

As it turns out, the Suburban evaporator actually has standard fitting sizes - Bill hadn't really looked at the unit closely enough. Hoses should be made up by the weekend, and I found a compressor mounting bracket at the boneyard today.

Thanks for the replies!

---> Bill

YOU STILL NEED ME? ACTUALLY I LOVE SKID ON FITTINGS---THEY MAKE ME ALOT OF MONEY. THESE "BARBED" FITTINGS ARE FAMOUS FOR LEAKS. TRY ALITTLE SILICONE BASED ADHESIVES AT THE FITTINGS not too much.

Thanks, Koolkar. I think we've got it under control for now. Bill found the fittings at an industrial hose supply house. I think he said the Suburban unit used a #6 and a #8 fitting. They will crimp the fittings on for him as soon as we can determine the needed lengths.

Appreciate the reply, anyway!

---> Bill

AW MAN----CRIMP FITTINGS!!! no money for koolkar! make sure you pull a good vacuum (28 hg.) for at least 1/2 hour. then close guages and let sit for a few minutes to see if the system leaks under vacuum. this is cheaper than shooting it full of r-134 and watching for stuff to spray out.

Koolkar, I do have one other question. The new front evaporator is already for R134a, but the used rear Suburban unit is an R-12 unit. Other than flushing, is there anything that needs to be changed with the expansion valve to work with R-134a?

I've been told that you generally need to change the orifice tube when changing refrigerants. If so, what do we need to ask for to get the proper part?

Thanks,

---> Bill

Also, Koolkar, good suggestion...we were planning to definitely vacuum-test the system. Bill has a commercial HVAC vacuum pump and is familiar with building refrigeration systems.

In A/C systems, cleanliness is next to godliness!!! If the rear unit has been sitting open for a while, remove the orifice tube and flush the evaporator coil and all related lines. Where I work, we use some stuff called Ken-Sol, which is a mixture of hexane and alcohol. It is a good degreaser and will rid the system of any traces of mineral oil, which is compatible with R-12 only.

Don't skimp on the condensor size, especially with R-134a. R-134a is not as efficient as R-12 and needs all the help it can get in getting rid of the heat, so go as big as you can with the condensor.

Also, on any crimp fitting, if you can turn the hose collar and hose on the 'stem', that is a spot that will leak. The crimp has to be tight to hold R-134a.

Applying vaccuum to an A/C system is a pretty good test for leaks, but it's real purpose is to 'boil' the water vapor out of the system. Water vapor combined with R-12 made hydrochloric acid, which eats aluminum. The little pieces of aluminum particles then float around in the system and plug the expansion valve (orifice tube) and damage the compressor. I assume the same is true for R-134a with respect to moisture. Ditto Koolkar on pulling a vaccuum for AT LEAST 1/2 hour.

Hope this helps--I guess I really didn't say anything that wasn't mentioned before. Good luck!!