Ac in 1988 ford class c stopped blowing cold air. Debating finding old freon or conversion. How much is normal price to convert over to the modern stuff?maybe I can still find some old freon and get some shop to put it in. Anybody have any experience with this dilemma?

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Hi Kevin,your chassis engine driven dash AC can be converted with a kit from any auto parts store.But first I would look for the leak.You may find a oily spot some where on the system.If you don't it may be leaking at the evaporator core in the dash.It's great if you can find and fix the leak but R134 with stop leak will sometimes do that for you.Also replacing the filter-dryer assembly with a new one before recharging will improve system performance.

  I agree with FIRST find the leak before converting, because otherwise you will keep adding freon till the cows come home, and as always, you change out the filter/dryer.....Its often the front compressor seal as evidenced by dark greasy oil in the front and clutch area. Although its more expensive, if you plan to keep the RV Id bite the bullet and get a new compressor (assuming old one leaks) and filter dryer and convert to R 134A. Around here thats like a $500 fix but it lasts, BTDT and got the T Shirt more then once........

 

 John T NOT an AC man but still my experience with a ton of older RV's

Thanks Jimco and John for the tips. I will definitely look for the leaks before doing anything. I think it is closer to 1000 bucks for the changeover out here in California, but it's hard to exist without ac. Rv does have those old time little triangle vent windows though.

turns out previous owner already made the changeover.  lucky me. shop added pound and a half and some dye. No obvious leaks.  We will see, thanks 

We did some work on our dash A/C on the Glastron and then replaced the dryer and pumped it down and put in Freon.  Did not last and so obviously have another leak in the old system. I ran the numbers and considering it takes about 25 horspower to run the compressor I figure this is 1-2 mpg loss/cost. On the other hand if I run the 4.5 Onan generator and put on the roof A/C I get a really cool interior and the onan only eats about 1/2 gal per hour of gas. I see it as a wash and I dont have to replace all my a/c dash parts and lay out $1,000! Just my point of view but my research says that many other motorhome folks even with the 40 foot diesel pushers do the same thing. Jim

That's pretty good thinking jimmy. I like the part about not laying out 1000 dollars!
I wonder what kind of freon they used in the old roof ACs? I got three cans of r12 I don't need now I don't think.

Most older roof AC's will use R22.And you will need to add a saddle valve to install it.But Kevin with your luck someone has already done that for you!

Haha. I hope so. I need to fire it up and see how she's blowen

How did you come up with a figure of 25 horsepower to run AC in any RV?  I don't believe it.  I'd guess it is more around 5 horse when running and a spike up to maybe 10 when the compressor first starts.  Many auto engines only put out 10- 20 horse when the engine is idling. If AC drew 25 horse, the engine would die. And yes, I'm aware of the fast-idle solenoid for AC.   My 1978 Toyota RV makes 90 horse max at 4800 RPM and around 10 horse with the engine idling.   AC works fine and when climbing a hill, I can only feel a slight power loss.

I've changed over many R12 systems.  Never bought a kit.  Just the new fittings, PAG oil, and sometimes new hoses.   AC rubber hoses made before the mid-90s are single-wall and leak-prone when used with 134A.  Smaller molecular structure.  All new rubber hoses now are "barrier" hoses.

John: It sounds as though you have a lot of experience with A/

C systems. When deciding how much HP is required to run the compressor things get real complicated as you know.  What type of freon is used, what type of compressor, is it a scroll, piston, wobble etc? What displacement of compressor? Total size of system? Then factor in the size and weight of the vehicle, frontal area, tire resistance while rolling? Then what size of drive motor is used? We can apply the same arguments to supercharging vs turbocharging.  I cant compare your obviously very efficient Toyota system to my old outdated Dodge system. I know that I could replace my old piston type of compressor for a newer model scroll and probably gain on the reduction of power required. I got my 25 HP number from researching on the internet. I think that if a compressor only used 5 hp there would not be a need for a relay to disengage it while in start mode nor would it be required to have  solenoid to increase speed while compressor is on? Anyway I will submit that there may be small compressors running small systems that only use 5 hp and inversely much larger MH systems may use a whole lot more power. 

My 1978 Toyota RV has a 1978 AC system. Denso compressor. 2.2 liter engine rated at a max of 90 horsepower @ 4800 RPM. When the engine idles it makes around 10 horse.  When the compressor is running, only labors the engine a little.   If it needed even 5 horse to run, it would almost kill the engine.  Being a 1978 vintage - I don't think I'd consider it "modern."  Not sure if it matters.   I have a 2002 Kia Sportage with a 2 liter engine and AC and it works about the same.

I have specs on the Delco AC system for my 1988 Chevy Suburban.  The DA6 (axial I think) compressor uses 5 horsepower (4 KW).

When I changed it from R12 to 134A using an 80% replacement charge, I noticed no difference in operation.

Also, a typical household or rooftop RV air-conditioner rated at 12,000 BTUs, running on electricity,  uses about 1 horsepower to operate.  Why would a belt driven unit draw 20X that amount?

One other comparison.  I can run my 13,000 BTU root-top RV air-conditioner (AC electric) plugged into a 5 1/2 horsepower gas-driven generator and the engine only gets worked hard when the AC first starts. 

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