AC conversion

jaiman · 08-14-2003, 10:11 AM

I have had my MH for a year now and am now thinking of getting the Engine AC up and running. I replaced the belt and still dont get cool air. When I move the controls I hear the typical sounds of clicks that most compressors make. So now I need to charge the system. Being an 81, it is the old environmentally unfriendly R-12? A conversion has not been done by the PO. Are the 134a conversions easy to install? Should I have a professional take care of it. Any advice would be greatly appreciated

Jai

wb13798 · 08-14-2003, 11:47 AM

i would recommend you get the system vacuumed and if no leaks go to auto zone and get a change over kit . follow directions and it should work. the auto zone kit has every thing in three cans so you dont have to get other additaves. like oil $8 extra in some of the kits.lol
al

IPM · 08-14-2003, 01:03 PM

It works. The evaporator and condensors are so large on these motorhomes that the 134a works well. I did it and did not even "pull" the vacuum or replace the reciever dryer because of lack of time (going camping!). It will be even cooler once I replace the receiver dryer (any good chevy dealer parts counter for approx $55) and properly evacuate the system.

Rebuilt, replacement ac pump can be had at autozone or such for about $100 plus core. If the rear mount plate does not install flush on the replacement pump (likely will not), then use a grinder to modify the rear plate to fit.

Here's a poor boys trick to "evacuate" the system. Start the engine and let it get hot. Shut it down and "open" the schrader valves on the ac. Vapor, gas, moisture, or what ever in the lines will then vent. Not perfect, but...................

For 134a, target no more than 28 psi on the low side at around 1500 rpm when adding it (if you have gauge). Don't overfill or it will not cool as well. I'd stop at 70% by weight max of original r12 capacity if ya don't have a guage.

ac belt will wrap the water pump, main, power steering, and ac

belt will jump off if all pulleys are not aligned in the same plain
align pulleys or add idler pulley in front of ac pulley to solve

gee, I seem to like to rattle on here...............

regards,

Mike

jaiman · 08-14-2003, 04:23 PM

ac belt will wrap the water pump, main, power steering, and ac

The belt on mine goes from the power steering to the ac only. I had a difficult time getting one to fit as the Napa guys book called out a shorter one yet.

Is the Schrader valve the valve resembling the air stem on a tire?

ALANSD · 08-14-2003, 05:13 PM

mine was already converted by the PO,but now needs a charge.
Should I buy the refill kit with the gauge included? Do I need it or just add the extra freon...also what does running the a/c do to your mileage?

My roof air keeps it relatively comfortable on all but the hottest days, but it means running the generator, which uses soem gas also, no big deal but if the front a/c is going to drop me to 5-6 mpg I won't be recharging it anytime soon.
It seems like the best thing I have done for cockpit coolness was to bypass the heater core. I noticed no difference in operating temp, as i had recently serviced the cooling system, putting in some coolant additive also.

wb13798 · 08-14-2003, 06:30 PM

alan
i havent noticed a drop i get about 7 with or without and most trips last month and this i use the overhaed and dash air. i keep hearing about the heater core last time i checked my heater valve stops the hot water from circulating. that is the valve that is in line on one of the heater hoses.
go to autozone they have a cheap ac kit. comes with a guage.

uncleneal · 08-14-2003, 07:47 PM

"Here's a poor boys trick to "evacuate" the system. Start the engine and let it get hot. Shut it down and "open" the schrader valves on the ac. Vapor, gas, moisture, or what ever in the lines will then vent. Not perfect, but................... "

Not perfect, and not legal either. Don't let the feds know you are venting R-12 freon into the air, its a violation of federal law. There are a/c mechanics in prison for doing that very same thing. IMHO the whole freon thing is a hoax, (Dupont's patent on R-12 has run out) but the feds don't know that, and they are rather humor-impaired about it.

Neal

jaiman · 08-14-2003, 07:54 PM

Thats what had me concerned the most. So I decided to do the right thing. Take the MH into a shop today and had them pressure test and convert the system for me. Got to love that cool breeze

Thanks to all who replied

Jai

IPM · 09-04-2003, 08:49 AM

ya fixing a dead system. Nothing but the dregs are vented. The r12 already leaked out.

uwe · 09-04-2003, 03:22 PM

The conversion from R12 to R134 is not very difficult, neither is it very expensive. It does require a conversion kit, and some special lubricant.
The kit has new valves and O-rings, and often also comes with the lubricant.
On my MB's it also required a different pressure sensor for the compressor safety shutoff, and a temp sensor of some sort, I forgot.
R134a does not contain ozone depleting chemicals, which R12 basically consists of. Not a hoax.
I had several cars converted, from R12 to R134a, and it has not been a problem in cooling efficiency. The last one i had done was a 73 MB Diesel with a York piston style compressor, and even that one works great. I had figured that the higher pressure would blow the head off the compressor, but so far so good.
My preference is to trust these jobs to professionals with the right evacuation equipment, and experience. They pull 30in of vacuum on the system, leak test it, and inject the precise amount of refrigerant for the application. Eyeballing these issues might or might not work to the system's full potential, though.
All my vehicles drop in performance and mileage when the A/C is on. The 73 is hilarious, in that it just about stops when the York kicks in. My van drops 1.5mpg with A/C on, in mixed city/fwy driving.