P8M4108a OTR a/c question

[chessie4905]

My 2003TDI never needed any ac service or freon added. 254,000 mi. Only car I've had that didn't need some kind of AC work.

[richard5933]

COMPLETION UPDATE:

Just picked up the bus and drove 40 minutes to get it home. Today's not particularly warm outside, but the a/c did make consistent cold air all the way home. The tech first ran a nitrogen pressure test with leak check yesterday. That tested fine so he proceeded to evacuate the system and left the vacuum all night. It held steady and didn't lose any vacuum. This morning he refilled with 25 pounds of refrigerant. The service writer was surprised at how much refrigerant the bus swallowed, until he peaked at the size of the evaporator and condensing coils. Big enough to cool a small office building.

The invoice shows that they used R438A25 R22 as the refrigerant, which seems to mean that they used one of the modern replacements for the r22. When I got home I did some research online, and I believe this refrigerant is commonly referred to as M099. The write ups seem to indicate that it's a direct replacement for the r22 with compatibility with the mineral oil used in the existing system. The only thing that the write up said was usually needed was installation of new seals.

Since we installed a new compressor (with new seals) I guess that this was the perfect time to make the switch. At least if there is a problem down the road I'll be able to get things repaired without having to swap refrigerants later on.

Surprise, surprise...the R438A costs just as much as the old r22. Go figure.

[luvrbus]

LOL cost a bunch of money to leave Chlorine out of the Freon one would guess 

[chessie4905]

https://www.amazon.com/CHEMOURS-R-438AX25-Refrigerant-Disposable-Cylinder/dp/B00HGIRURA/ref=sr_1_2?ie=UTF8&qid=1529696426&sr=8-2&keywords=r438a+refrigerant

[richard5933]

Brief update on the OTR a/c after the trip to Wyoming and back...

There were two areas of concern regarding how the unit would perform after the update:

The first was the slightly larger clutch pulley at 6" instead of the original 5.5" diameter. The new compressor with the larger pulley worked just fine. It might have taken a couple of minutes longer for the system to reach full cooling capacity, but I really couldn't say so definitively.

The other concern was the replacement refrigerant, M099. Happy to report that the new refrigerant seems to work just fine.

After about twenty minutes on the road, the entire coach was easily kept at a comfortable 72 degrees in spite of outside temps in the upper nineties with full sun. If I had the temp control knob on the dash set to max cool, it got meat-locker cold in there, especially at the start of the day when the outside temps were cooler. The driver's area was slightly warmer due to the sun beaming through the windshield, but nothing the driver's fan couldn't cope with.

I'm really glad that when I struggled to get the heating circulation (booster) pump replaced/rebuilt I also had the water modulating valve replaced with NOS from Luke. The water modulating valve is what allows the temp to be moderated by running the heat as necessary to keep the coach at the desired temp. The a/c compressor runs constantly when on, so the only way to moderate the temp is through this system.

I know that now everyone has or wants the OTR HVAC system, but if there is anyone deciding to keep or scrap the system I'd encourage you to keep it if the system is salvageable.

[chessie4905]

You'll feel that way till the next time it goes down and costs $$$. Glad it is working fine.