PREVOST, The Ultimate Class

R-12 Over the Road Air?           

One of the nagging concerns some Prevost owners face is what to do with the over-the-road air conditioning systems which are still holding R-12 Freon. The ‘fix’ if you take your magnificent machine to a Prevost service facility is to replace the hoses from the pump to the condenser units, do some serious work to the unloaders and to the pump and replace the refrigerant with 134a. Depending upon the conversion equipment between the engine compartment and the over-the-road compartment, it is likely you will get an estimate of between $6000 to $8000 for standard Prevost warranted service. One year parts and labor.

If your over-the-road air conditioning is operating well, the recommendation here is to leave it alone. The axiom of, "if it ain’t broken, don’t fix it," certainly applies. As refrigerants go, R-12 seems to be a better refrigerant than 134a. It does have the attention of EPA and others as being troublesome...and has become very expensive and hard to find over the last few years, if you can find it at all. However, if you find that the over-the-road air system is not operating up to snuff you have at least two options.

The first option is to find where the R-12 is leaking, which is probably very little, and fix it. Once repaired, you may find you can replace the evacuated R-12, add a couple of pounds of R-12, if you can find it, and you are good for another several years. Hopefully, if you have experienced a minor leak, this will be a quick and the least expensive course to follow.

If you choose to upgrade to 134a, or if the R-12 refrigerant has evacuated itself or worse, the choice you have now is how to upgrade your over-the-road air conditioning system.

Here’s an idea, a shortcut which may provide a fix that will be less costly than the complete redo, which will provide years of service and is much quicker.

Keep in mind that one of the shortcomings of 134a is that it can react quite badly to convention lubricants which will inevitably come into contact with it at the pump; any contaminants in the pump/hose/condenser system will also cause trouble.

Here is what many owners have done to do an upgrade at minimal cost and hassle. And it seems to be a lasting fix:

First, the R-12 will have to be evacuated and stored. Many bus companies, Prevost-knowledgeable service shops and the many dealerships are still able to provide this service. Last time we checked, R-12 was about $55 a pound, if you could find it. The original cost was about $5 a pound. (Now you can kind of get the drift of why constant refilling of the original system with R-12 can be expen$ive). Once evacuated, insure the system has no leaks.

Next, the matter of the big 3-cylinder pump on the right hand side of the engine compartment. One thing we know is that the oil in the pump is not going to make 134a refrigerant very happy. The fix here is to replace the lubricant with synthetic oil. This will minimize any cross-contamination with the 134a. Keeping standard lubricants in the pump will eventually cause you difficulties: This is the time to replace the lubricant.

The final step here is to replace the unloaders with 134a unloaders and refill the system with 134a.

Now, of course, you have the opportunity to replace that old, faded R-12 sticker with a 134a sticker with an upgraded over-the-road air conditioning system and you are done.

It is very likely that most shops will not provide a warranty for this fix. Certainly Prevost will not, as the company specifically does not want to challenge its standing as the top dog of premier service. However, it is the technique which Prevost itself uses with the buses it resells from fleets to charter operators, so you can judge for yourself if it is a good idea. (Hint, hint).

There are many sources for completing this repair/upgrade. There are a ton of big vehicles run by charter companies, bus lines, trucking companies and the like which have already experienced this dilemma. Their orientation is always to provide a reliable fix at minimum cost; and that is what is being discussed here.

Of course, the above fix will not apply to any situation where broken lines, deteriorated hoses or deficient condensers may exist; these will require complete repair and replacement, as needed. These seem to be rare in a well-maintained bus. For the owner who is interested in the 134a upgrade or minor repair and replacement, it will serve the owner well.

Stay coool.

Jeff Raymond