a/c dash driver conversion

[freds]

Ok my 1980 Prevost has a dash A/C system (not whole bus) that has a big R12 Placard on the air filter.

I am sort of eyeing a trip to south Texas as soon as it get's repaired in LA to potentially see the first liftoff and maybe landing of SpaceX's fully reusable rocket, depending on when it's roadable again. Given the modern heat wave's I don't want to stroke out if I attempt this.

Heck at this point I don't even know how I would turn it on given a PO (2nd generation) partially competed dash upgrade.

Anyway the PO basically ran the diesel generator and the two roof air conditioners. However I did notice that he had a big fan taped to the dash also which I have removed.

After fixing diesel fuel supply air leaks in fueling the generator the mechanics are telling me that it is clapped out and not to run it.

While I do have solar it can't handle both air conditioner unit's from solar panel production alone.

I am noodling away on a DC-DC converter to feed extra power from the buses 24V alternator to help make up the solar short fall in power.

I have not idea of the condition of the flexible line/condensers, etc.

Should I switch to R134a, R12A or heck propane...

So anyway any advice is appreciated!!!

[RichardEntrekin]

Before you put any refrigerant in the system, do yourself a favor and pressure test with nitrogen. No need in putting in anything if it leaks like a sieve.

[freds]

Thanks

[Jim Blackwood]

If you don't have nitrogen you can still pressure check it with compressed air.

I'd suggest propane. I have one vehicle running it and it puts out 20-30 degree air at the vents. Now admittedly that is probably going to eventually freeze up but when was the last time you saw less than 40 degree vent air?

Jim

[freds]

Actually looking at R-152A which is air duster gas.

Look's like O'Reilly rents/loans tools to do this.

[rancher]

Fred I worked in commercial  refrigeration for years and did a lot of change overs on big coolers from R-12 to R-134A and they worked out well. Have done many cars and trucks and many pieces of farm equipment. Normally on mobile equipment I would test the system with Nitrogen two to three hundred pounds for the big leaks. Look the hoses over real good. A lot of times the hoses will need to be changed to make a tight system. I would flush the system. Change out the expansion valve and compressor unless it was fairly new and if it was I would just change out the oil. Vacuum the system down to micron level and charge it. You have to have a tight system to keep R-13A in. If you have to hire this done it won't be cheap to get it going again. I don't think one coach I have looked at the bus air has been working.

[freds]

Fred I worked in commercial  refrigeration for years and did a lot of change overs on big coolers from R-12 to R-134A and they worked out well.  You have to have a tight system to keep R-13A in. If you have to hire this done it won't be cheap to get it going again. I don't think one coach I have looked at the bus air has been working.

I agree that it's probably a hopeless case given that the system is 42 years old. But I thought as a quick experiment I could do the duster gas R-152A which is cheap $30-50 to try and no big deal if it leaks out.

There are numerous videos on YouTube of people doing this with older cars.

https://www.youtube.com/watch?v=3wkBnhcyO3Y

I also just located a 30Llb unopened Envirosafe R12a nearby for $125.00 and 3 14oz R12 can's for $75.00. Nearby on Craigslist.

I have no idea what kind of charge that this unit would take. The maintenance manual says 25 lbs for the full bus air conditioner but nothing about the smaller drivers dash A/C.

I would say the compressor is about the size you would see on a semi-truck...

[chessie4905]

do yourself a favor. Pressurize system first with an air supply, preferably, nitrogen or co2. If you have a vacuum pump for that kind of work and gauges, draw it down to a vacuum and see if it holds. I don't  believe the hard connections used o ring seals yet. I would suspect compressor shaft sealers or a hole of some size in condenser would be the first suspects. Once it quickly looses vacuum, then you'll  need to pressurize system and get some leak detector. liquid or electronic. Refrigerant is too expensive to fill and hope for the best.

[rancher]

Fred I wasn't saying fixing your AC is a lost cause at all. I have  1979 JD 4440 tractor that is on 134A and I never add refrigerant to the system and I run the tractor a couple hundred hours every summer on a bat wing mower. AC will freeze you out of the cab You just need to test the system and see what it needs.

[freds]

Fred I wasn't saying fixing your AC is a lost cause at all. You just need to test the system and see what it needs.

Thanks this is still a bit academic as the bus is still going through it's collision repair in LA and I am in Seattle waiting for it to be done.

So not sure how much work I will do while on the road.

[freds]

Ok I been watching more YouTube videos. So if I pull the trigger on this I am thinking the initial steps would be:

1. Get loaner gauge's from O'Reilly Auto Parts
2. Test if the low side has pressure.
3. If the low side has pressure take it somewhere to have the system evacuated of R12. If pressure is greater than X?

What are the suggestions if there is no pressure?

Should I just take it apart and start replacing things like the compressor, dryer and O-rings?

[luvrbus]

Is that a aftermarket dash air on your bus ?,if so those can be made new again for under a 1000 bucks with a new compressor ,you can purchase anything you will need from ProAir

[freds]

Is that a aftermarket dash air on your bus ?,if so those can be made new again for under a 1000 bucks with a new compressor ,you can purchase anything you will need from ProAir

Nope it's OEM with the bus. It's show's up in the parts manual but nothing about the motorhome version in the maintenance manual.

I just had a horrible thought and can't see in the part's diagrams where you would attach the gauges on the high and low sides. Is it some older standard?

[Jim Blackwood]

I think that qualifies as a "small" system based on that compressor type. You need to find out what oil is used in the system if you want to change refrigerants.

PAO, PAG and mineral oil are propane compatible.

One advantage of the propane is that it is a larger molecule so isn't as prone to leaking out as r134. To get your charge right you need a pressure/temperature chart:

http://virtualmark.net/wx/pressure.htm

Then use your high side pressure to get the condensing temperature from the chart.

Next measure the temperature of your liquid line, probably up front where it goes into the evaporator. Subtract that from your chart number and you have your Subcool value which should be around 10 degrees under the condensing temperature of the propane at that pressure (from the chart) if your charge is correct.

If your lubricant oil is compatible with propane you can go ahead and charge the system, see how well it works, and give it a few days to see if it leaks down. A little side benefit is if it is leaking in any significant amount you should be able to smell it.

If you don't see any service fittings on the compressor lines, look at the lines at the condenser. There also could be fittings at the evaporator.

Jim

[luvrbus]

That is a old Harrison type compressor they are companiable with almost any type freon with the right oil,if the compressor is bad 4 seasons makes a replacement for about 200 to $250.00,Must be conversion shell without the full bus air dash air only dash air my Vogue had that with the test ports under the dash