P8M4108a OTR a/c question

[richard5933]

If you continue to have some leak issues, you'll wish you would have bitten the bullet now and converted to R 134. A lot of the Prevost cost will be to upgrade to better hoses. The molecules of R134 are much smaller and can pass slowly through the old hose material. Plus some pressure control units need replaced due to operating characteristics of 134 vs. 22.

I did ask about the conversion, and apparently 134 is not a viable replacement for r22. The pressure differences are too great, from what I understand. There are a couple of r22 replacements in use for home a/c systems, and I'm hoping that before it's needed in our bus they'll get something that works reliable in the system.

The only hoses I see in our system are those that are between the compressor and the copper tubing. Both the condenser coil and the evaporator coil appear to be mounted with sweated on copper lines.

If you've got some information about using 134 to replace r22 I'd love to see it, as so far nothing I've found makes it seem doable in a simple method.

[muldoonman]

The reason the Prevost deal is so expensive is they change/replace everything even the Compressor, Expansion Valves and  all Hoses, even if you have put the right kind on for R134. A complete system change out. From front to back.  The Condenser side to Evaporator side across coach is a biggie they said as they might have to pull tanks out as the hoses go across. They Say that's the only way they can warranty it for a year. Yeah, like I would believe that.

[luvrbus]

The reason the Prevost deal is so expensive is they change/replace everything even the Compressor, Expansion Valves and  all Hoses, even if you have put the right kind on for R134. A complete system change out. From front to back.  The Condenser side to Evaporator side across coach is a biggie they said as they might have to pull tanks out as the hoses go across. They Say that's the only way they can warranty it for a year. Yeah, like I would believe that.

Naw that is another Prevost way of saying we don't won't to fool with it at one time it cost 3 to 4 k at Prevost in Ca of all places

[chessie4905]

Yes, thats something nice about GMs, they did it without a lot of hoses. The other brands never figured that out.
I don't blame Prevost, as they are a premium brand, at least to many that aren't necessarily on this board. They are going to insure you get a solid issue free ac upgrade. I don't care for that price, but do the labor yourself and save a lot of those bucks.
As earlier in a reference given, there are other refrigerants that will work in r22 systems that don't harm the environment, but I don't know what price/lb.
Many bus companies and manufacturers felt r134 could be compatible with their systems,and considered the ample availability of the r134.
The outfit servicing your 4108 may not want to get into changing refrigerant issues.

[luvrbus]

Gm sure used a funky design with the clutch and drive though,I doubt any updated compressor will fit or work besides the Frigidaire in that space ,I always believed the drive design was the cause of the seal failure on the GM buses that is a tough seal to to prevent from leaking over time,back then r 22 was cheap you just kept on adding Freon it wasn't a big deal      

[richard5933]

Here's a picture of the compressor.

[chessie4905]

Is there only one? GM book lists a dual a6 design. Maybe the 4108 only needed one. That is a larger model of the one GM used in cars for years and years. Other than seal leakage, it was pretty much bullet proof. They did have a tendency to leak from lack of use. The other design in the coaches was a bigger v type that ran from a driveshaft off front of engine. They had a clutch to operate it. Drivers were cautioned to never engage it above idle or it would tear up clutch eventually.
Do a google and see if anybody rebuilds it to r22 or other specs.

[richard5933]

We've got just the one. Section 26C of the maintenance manual shows this option. There was another option with dual compressors, but this coach did not ever have that dual option. I'm assuming that being sold originally in the NJ area there was not felt to be enough need for that.

I'm hoping that you're correct about the bullet-proof part, and that once Luke & Bill install the new seals we'll be good to go. This a/c compressor definitely did not get very much use and sat for substantial amount of time without running the a/c. We're rooting for that the be the cause.

[luvrbus]

That is strange Bill's 4905 has a 4 cylinder aluminum Frigidaire V type AC compressor just like the one used in the GM transit buses. I know the transit buses used it because I bought one from a GM transit for his, the clutch looks like a mushroom type clutch and it is factory AC when it works 

[richard5933]

That is strange Bill's 4905 has a 4 cylinder aluminum Frigidaire V type AC compressor just like the one used in the GM transit buses. I know the transit buses used it because I bought one from a GM transit for his, the clutch looks like a mushroom type clutch and it is factory AC when it works 

Strange good, I hope.

Our old 4106 actually had something similar to this compressor, only it had two of them. They were installed in place of what was OEM for the 4106. From the little I know about these things, this type of compressor is pretty good and can usually be re-sealed with success.

[luvrbus]

That compressor was the work horse for years,you got to watch the oil though they won't handle many Freon charges without adding oil or they seize up,I am sure your AC guy will know how much oil it will take for your system which is going to be more than a average car 

[richard5933]

Got an update from Luke. Apparently there is something wrong with the compressor shaft, and after two seal kits they cannot get the compressor to seal and hold pressure. Not good news. Luke is out of town till Tuesday, and when he gets back he is going to try and find a replacement compressor.

My parts book is in the bus at the shop. Anyone know what the part number is on this type of compressor? I'd like to do some reading on the compressor but can't find anything online without a part number or model number on the compressor.

Hopefully Luke will be able to come up with a replacement compressor, or another compressor that can be made to work. If not, I'll be looking for a 'B' plan to keep the OTR running. Seems to me that since the only function of the compressor is to pump refrigerant, there has to be something else out there that can do the job if this particular compressor is NLA. Fortunately the a/c compressor is the only thing on the belt, and there is lots of room in the area to accommodate options if one can be found.

Still want very much to keep the OTR in place, since the alternative to stay cool on the road would involve a better house a/c system as well as a better generator. I wouldn't want to run the old Perkins that many hours, both due to its age and the high fuel consumption, and the current basement a/c units would have trouble keeping the front of the bus comfortable on sunny days.

[luvrbus]

Call Welch Industries in GA 770-474-1150 he is the bus AC expert and he will have a replacement 

[richard5933]

Call Welch Industries in GA 770-474-1150 he is the bus AC expert and he will have a replacement 

Do you know what the compressor's model number is? Or, would they be able to look it up by the coach's model number?

[richard5933]

Looks to me like an A6 compressor, but boy oh boy are there a lot of variants out there. Switch type, CCW vs CW, 12v vs 24v, pulley type, pulley size, etc, etc.

I'm going to let Luke attack this one when he gets back, since he has the know-how and experience to get the right one. That is, unless someone just happens to have a working a/c compressor off a 4108a sitting around that needs a good home.

At least there are lots of places still selling the compressors, and while not cheap it's still going to be less than the refrigerant going into it.