Compressed Air System Frozen

[thebunns]

When starting my '97 Fleetwood Discovery in cold weather the cutoff valve opens within 10 seconds. That tells me that there is ice someplace beyond the valve & before the tanks. I put a heater on the air dryer for 12 hours along with plugging in the block heater. I restarted the engine & had the same results. The red & green needles do not move. Where should I apply heat for the next try at thawing out the frozen spot? Or, is there another remedy short of waiting until spring?

[Cypressloser]

Part of the daily maintenance should be draining water from the air system.
You probably also have an air dryer or alcohol sniffer installed already and if you're not familiar with it's inner workings have it checked out by a mechanic.

[Ilvmygt]

If you have moisture downstream from the Air Dryer, your air Dryer is not functioning properly. When was the last time it was serviced? Since the cutoff valve opens so soon it may be defective. You might try changing it.

[8.3Oilbuner]

HI Thebunns; Yes, colder in eastern Washington that over here in the Puget Sound area. Your problem had a discussion here in this forum not too long ago. Most mentioned that you might have to add air line antifreeze to the air line, can't remember exactly where to the system, or get it in a heated garage for at least 24 hours. You might try a search at the top right of this page in this forum to see if you can find the recent posts and what the remedy's are. Do you have the 12V heater in the bottom side of your air dryer? If you do you might want to see if you have 12V to the heater. Beyond that, I can't suggest anything else at the moment. Doesn't get cold enough here on the west side for that problem. Good luck!

[twinboat]

Put the heat at the wet tank. It is where the air goes after the air dryer. It is also the tank that sends the signal to cut the compressor off.

If you have only 2 tanks, look for the longer one with a welded seam near one end. The shorter side is the wet tank and may have water in it.

There is a double check valve Tee, from the wet tank, to the 2 tanks with gauges. It may be frozen closed.

If that don't work, pour alcohol into the output line on the compressor.

[BFlinn181]

I'd go to a home improvement store and buy a couple of plastic drop cloths. Tent in the rear of the RV and stick a heater or two in the enclosure. The heater just blowing on the dryer wasn't enough, enclose more of the underside to defrost. Then do as the others have said about perhaps changing out the air dryer, bleed all water from your tanks, then add air brake anti-freeze to the system, as close to the air dryer as possible.

[CountryB]

If you want to add "brake system alcohol" to the system, the best place is at the air compressor discharge line (assuming you can get to it). You would unscrew the braided ss line and pour an ounce or two of alcohol in then reconnect the line to air compressor. This will push the alcohol to the point of obstruction.

Note that this was common when I was in the business in the 70s and 80s, however Bendix (maker of most of the air valves/components) does not recommend this as they say the alcohol can wash the lubricants off the o-rings and rubber parts in the valves. I never saw a problem with this practice in my 20 years, but maybe the valve internals have changed since then (or more study was done on the practice).

[thebunns]

After reading all the above posts, I found a blown fuse going to the heater on the bottom of the air dryer. After replacing it, I ran the motor for 1/2 hour but it did not thaw the ice. Question: is the new warm air going to thaw the system if I run it long enough or should I dump a little air brake antifreeze into the line coming off the compressor? Right now I shut the motor off, have plywood along the sides about halfway to the front and 75,000 BTU's of air blowing into the area. I'm going to check it in 2-3 hours.

[BFlinn181]

If you have it tented in, I'd give it time to melt the ice. You could also divert the engine radiator heat to the tented area, although at idle not much heat would be created. If it's windy, all bets are off.

Be sure to use proper airline antifreeze. Online some suggest rubbing alcohol. It could be bad for O-rings and other gaskets, in addition, rubbing alcohol comes in various different dilutions from 99% down to 30%. The weaker solutions would have more water in them.

[twinboat]

What is happening when you say the cutoff valve is opening ?

Is the air dryer unloading ( blowing off ) like normal ?

Or is the pressure relief, safety valve opening ? Not normal.

The red and green gauge needles are at what pressure ?

[thebunns]

The problem is solved! After six hours of heat blowing underneath the rear end, the system is back to normal. Now, I'll have to wait & see what happens the first of February when I start it up again. Now that the air dryer heater is working everything should be back to normal. I'll deal with the water in the system in the spring, providing that the heater can handle it two or three more times.

[BFlinn181]

Originally Posted by thebunns

The problem is solved! After six hours of heat blowing underneath the rear end, the system is back to normal. Now, I'll have to wait & see what happens the first of February when I start it up again. Now that the air dryer heater is working everything should be back to normal. I'll deal with the water in the system in the spring, providing that the heater can handle it two or three more times.

Now that the ice is melted and you can air up, I'd drive it a bit to help move the water out of the lines where it froze. Pull the lanyards or open the drain valves on each air tank too. If you can find a heated garage you could park the RV in for a day or two, that would help also. To just leave it where it is, 1st of Feb might be another exercise in defrosting the air system.

[lancslad]

I managed a fleet of trucks at a container terminal. Our rule of thumb was pull the lanyards to drain the air system every time we fuelled up. Only takes 30 seconds to avoid a big headache.

[thebunns]

All nice thoughts, folks! I'm in the mountains & the motorhome doesn't go anywhere until spring. The snow hasn't gotten going much yet but I couldn't back it six feet without getting stuck. As I said, I'll deal with it in 2-3 months.