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1983 Chevy Van/Motorhome A/C Repair

steve48348 on Thu June 17, 2010 11:58 AM User is offlineView users profile

Year: 1983
Make: Chevy
Model: Van 30 (1-ton)
Engine Size: 6.2
Refrigerant Type: R134a
Country of Origin: United States

I bought this motorhome last year and I'm in the process of fixing it up.
It has a 6.2 Ltr diesel engine. The original compressor is a Sanden SD-508. Supposedly it had been converted from R12 to R134a. The compressor does have a low pressure service port for R134a on the back side.
The drive belt for the A/C is missing, and the clutch assembly is covered with an oily substance, which does not seem to be motor oil. I'm suspecting the shaft seal on the compressor is bad but I don't know for sure.
To be on the safe side I was just gonna replace the compressor with a Sanden SD5H14, which, from what I read is the R134a equivalent to the original SD-508.
Here are the questions I have.
1. Is the SD5H14 a good choice to replace the original SD-508, or is there something different I should rather get?
2. The SD5H14 does not have any service ports. I noticed newer cars usually have the service ports somewhere in the lines/hoses not on the compressor. What's the best way of getting a service port in there?
3. Do I only need a low pressure port in order to fill the system? What's the high pressure port for?
4. The line/hose connections I currently have are all screw clamp style. Newer cars usually have permanent crimp style connections. Should all the hoses and lines be replaced since they could be close to 30 years old?
5. I did not find a low or high pressure switch in the system. Shouldn't I have at least a high pressure switch to protect the system components? I know R134a uses higher pressures than R12 used to. Is there a universal low and/or high pressure switch available I can use?
6. Should there be some sort of orifice tube and/or filter somewhere in the system that should be replaced?
That's all the questions I can think of at this moment. I greatly appreciate you guy's time and welcome any suggestions and advice!

bohica2xo on Thu June 17, 2010 12:57 PM User is offline

Generally a missing compressor belt is an indication there was a reason to stop running the compressor. replacing an unknown & disabled compressor is a safe bet.

Your system is an aftermarket unit, with hose clamps & barbed fittings. While it can be retrofitted, it will have a tube & fin type condensor that is not the best choice for 134a in terms of capacity.

1) Sandens are good compressors. Replacing the compressor with one that fits & has the same capacity should be fine. Adding a larger compressor would be folly without adding a bigger condensor and possibly evaporator.

2) Service ports can be added to lines or components. The Sanden & Seltec compressors have many rear covers with various fitting arrangments, and the site sponsor can probably get you a replacement compressor with service ports.

3) You really need BOTH service ports to properly service a system. Diagnosis with only a low side gauge is sketchy at best, and can be dangerous. High side pressures tell us if the condensor is working properly, if the system is overcharged, or leaking...

4) That aftermarket style connection used non-barrier hose. I don't believe that type of hose is available any longer. Barrier hose does not work well on old style barbed fittings. The fittings can be changed or modified to use barrier hose. The clamps should be upgraded as well. There are a few threads here about this very issue, it is more info than I care to type in a single post.

5) Your system probably used a TXV & a freeze switch. Both are at the evaporator. A high pressure switch is mandatory for 134a conversions, and the site sponsor sells several types.

6) On a TXV system, the receiver - dryer is the filter. There may be a screen at the inlet of the TXV as well. The dryer gets replaces, and the TXV should be inspected or replaced.


The first thing you should check is the system pressure - hopefully it still has a bit of positive pressure. I would recommend a quality set of gauges, and a good vac pump. The site sponsor sells a very nice DIY kit with a pump, gauges etc. for a great price.

A poster here (NickD) recently did a lot of work on a motorhome system, and posted good pics & descriptions. A search should bring up the threads.

B.



-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Thu June 17, 2010 2:51 PM User is offline

Great reply, Bohica, don't have anything to add. We used my motorhome yesterday as a moving van for our daughter, wife said the AC is still way too cold. Thought the prices on these things hit bottom four years ago, ran across one 13 years younger and much better shape than mind was, at nearly the same price. Dang, I guess one motorhome is enough. RV dealers are sure hurting around here, expecting my local one to go out of business soon.

Diesel sounds great, but with the huge extra price they are charging for diesel fuel around here, the cost per mile is getting very close to that of gas. They get you one way or the other.

steve48348 on Mon June 21, 2010 8:09 PM User is offlineView users profile

Thanks a lot for the excellent information. I will probably get the DIY charge kit since I have 2 cars besides the motorhome that are getting older and one of them I think is in need of topping off the refrigerant. So in the long run it should save some money being able to do it myself.
I have a few follow-up questions.

1) You suggested the original R12 tube-and-fin style condenser is less effective with R134 and that I'd be better off getting one of the high efficiency condensers made for R134. I have some room to spare in front of the radiator so I could actually get a larger condenser than what I have right now. Can a condenser be too big at some point, or is the rule the bigger the better? Also, in order to (possibly later) add a second evaporator core to the system in order to cool not just the driver cabin but also the living area of the motorhome, similar to "rear air" in a minivan, would I be ok with a larger condenser, or would the compressor have to be larger also?

2) When you say larger compressor does this refer to displacement only or are there some other specs?

3) Can I go with a larger compressor and a larger condenser but the original size evaporator for now in order to be able to add a second evaporator later?

4) What does the term barrier hose mean? Does this kind of hose hold the refrigerant better?

5) You said hopefully the system does still have some pressure. What if not?

Thanks everybody!
Steve

steve48348 on Mon June 21, 2010 8:24 PM User is offlineView users profile

Just a few thoughts following up on NickD's post.

I'm not even looking what's available in the Motorhome market right now cause I know I would kick myself in the butt for not getting something in better condition than what mine was. Price wise it was ok, just needed a lot more work than what I had initially bargained for.

I spent $2500 for the motorhome, plus approx. $2500 for tires, new roof air, lots of little stuff, and still going...
I wanted a diesel because in this price/age range a gas powered motorhome isn't getting anymore than 10 to 12 mpg at best.
When I picked up mine last summer I got about 22 mpg over a 400 mile stretch, pulling my Saturn SL behind it.
And I can later, when everything else is done, add a second tank (plus a few extra things) to run it on vegetable oil.

Bohica2xo said you had done some a/c work on your motorhome.
Where can I find these posts? I'd be very interested in reading up on it.

Steve

bohica2xo on Mon June 21, 2010 11:47 PM User is offline

Steve:

It is almost impossible to have too much condensor. If you plan to upgrade, use the largest parallel flow unit that will fit - especially if you plan to add an evaporator later. The 508 is a bit small for a dual evaporator system.

A larger compressor will give you more capacity. If you have an excess, it will tend to cycle more - unless it is a variable displacment type. Any larger compressor would mean fabricating or modifying brackets. If you are up for brackets & modifying the system, I would fit a variable displacement V7 unit as a first choice.

Barrier hose has a multi layer construction to hold the refrigerant longer. It has a thin nylon liner in the inner bore.

A system still under pressure means it has smaller leaks - and you may be able to locate them with the remaining charge. A system that is at atmospheric may have huge holes in it, or may have been open for a decade - no way to know for sure.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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