[Corey]

Prevost Mira Loma replaced the liquid solenoid valve and the temperature sensor in the driver’s air system. Cold air temps at vents now @48*F. Green light not illuminating when cooling tho. Louie (great Tech) thinks the problem is probably in the display.

He also suggested that the best and less troublesome way to run your dash A/C is to set it at 55* and control the temperature by fan speed. This way you’re not constantly working the valves switching from cooling to heating to maintain the set temp. Just passing that suggestion along for what it’s worth.

While I was there at Prevost another issue popped up. I’ll give you the quick version as it is off topic.

Prevost Mira Loma does a “free” under carriage inspection each time your bus is on their lift with emphasis on safety related items. They called me and suggested I change the air dryer due to the oil they found all around it. I responded that Prevost Dallas replaced the air compressor last October because they found oil by the air dryer and they probably just didn’t clean the area after changing the air dryer.

Now it should go without saying that when the air compressor is changed due to its passing oil into the air system, so should the air dryer as it was probablly oily and not capable of working properly. I did notice that Prevost Dallas had not charged me for a new air dryer. I specifically asked them if the air dryer was changed. They said it was and the cost was probably included in the total cost of the repair and not shown as a line item. So I didn’t question it anymore and assumed all was well.

I had checked the air system for water several times since then and the system was dry as a bone. Threre weeks ago I had Jeff do a oil change during which he checked the air tanks and air system. His comment to me was that the air system was water free and the air was good and dry.

I decided to change it anyway just to make sure that wasn’t the old air dryer still on there. Louie came in on

Saturday just to change that air dryer for me. Well, it was the old air dryer and still had some residual oil in it. I’m glad I decided to make sure the air dryer is in proper condition. But I’m at a loss to understand how the air system remained water and moisture free with that oily air dryer still in place??

[John]

Just a guess…but the old cartridge was still probably good enough yet to do its job. Geo.

[Randall]

I have the original air dryer, but the cartridges are routinely replaced.

Compressors pass oil. As they age they pass more oil but don’t think of that as a liquid or even a significant amount. It is a mist carried by the compressed air. The air dryer itself is not impacted by the oil that is carried, especially if the dryer cartridge is routinely changed before the oil mist is seen around the discharge area.

[Archived]

[Corey]

Dan,

Your dash air compressor is in the engine compartment and freon is added at the compressor.

[Doug]

[Dorel]

Chuck, posted this suggestion from Prevost service tech…

Set your control AC / HEAT temp down to ,55 deg or all the way up 85 deg. Then use air control for regulation ? Yes, I heard the same speech when complained I was unable to control temp settings.

Now for the rest of the story……

I spent a lot of time researching why my dash air fan located under the dash in an air box would sometimes go from set speed to off then cycle continuously. Most techs seemed to be in agreement I had a ground issue. Yes, I did but also a sensor issue. Prevost has an upgraded sensor which is included in the replacement dash control unit.

For what ever reason your dash air sensor is bundled in the wiring package behind the dash from the factory. Dash air never had a chance to work correctly.

Prevost, bus salesmen, service techs tell owners to set the control at 55 deg max cool or 85 deg max heat.

I located mine behind the dash stuffed in a corner loop and nearly impossible to ever sense the actual temp in the front of the bus. After I ordered the dash control unit I found packaged an upgrade repair part a much more advanced sensor. This new sensor is now mounted under the dash above the drivers right leg. With the installation of the new sensor and an actual location helpful to operation our dash air functions very accurate in cold and heat settings.

Yes drivers….this is your temp sensor buried behind the dash in some wire bundle. The sensor is the small black tip at end of wire. Appox. size 3/16 wide by 1 /4 by 1/16 thick.

Here is the upgrade sensor mounted above drivers right leg. Clear tube carries air from the AC/Heat air box. Sensor is protected by round cone.

With this sensor upgrade control is very accurate.

New dash head and upgraded sensor kit…..$800

[AL]

Al, is the kit Based on your VIN #?

Easy to identifty by Prevost parts or additional info was required?

Thanks

[Dorel]

I’am pretty sure they are the same being only 20 numbers apart and we both have OTR air.

Do you have operation problems with temp. control settings ?

[Doug]

Yes, only with driver air section, besides Prevost known air flow issue on driver side, controller display Temp adjustment to 72 or 70F it does not bring the temps down for optimal driving conditions.

Last trip I lowered temp to 63-65F while driving, it was better….did not lower to 55F yet, I thought I should start high and go towards 55F to test the tech suggestion, but this is not the resolution.

I probably need to do what you did, but need time to take the dash apart, where many say it is a challenge due to lack of drawings/how dash was initially put together by Marathon.

I could use some of your in work in progress pictures when you changed yours.

Thanks.

[Archived]

Most if not all buses have temp control issues. My post was to make owners aware that there is a reason tech’s are telling owners to dial all the way down or all the way up.

IMHO … temp cannot function correctly due to where the sensor ended up in dash.

Almost positive seated passenger bus drivers had a few complaints on there driving comfort.

[Archived]

My drivers air blower is crapping out (sounds like a piece of wood is in the squirrel cage). Is the only way to replace it through the floor slide opening or the removal of the front stainless skin? I have 4 paint colors on rivets on the front! I have OTR.

[Archived]

The first step obviously has to be to identify the source of the leak. It could be as simple as a fitting, or a compressor seal, or as bad as a leaky evaporator.

The best place to identify the source is going to be either Prevost or a facility that specializes in Prevost coaches, preferably one dealing with conversions.

[Bernie]

[Mike]

Where are you Don, we can help refer you to someone. I’m assuming your using 134a and not R-12. The York compressors don’t last long, I’m on my 3rd in 4+ years. Like Jon said, you need to identify the leak and go from there with a compressor (they’re cheap) dryer, vacuum and Freon charge.