Air Dryer Purging when Engine if Off

[flyboy013]

I have a 2018 Newmar Mountain Aire on a Spartan K3 chassis. For some time (probably ever since I owned the coach) I would notice that the "Front"/Secondary air tank would have about 60-70 psi of air after a few days. I figured I had a slow leak and I've had one or two of those leaks repair at the Hadley air manifold. But I've started to notice that the air dryer would randomly purge air while parked and not running. I recently noticed it about 15 minutes after shutting down the engine but I've noticed it other times, but at the time didn't think much of it.

It would seem to me that since the air dryer purges air after the tanks are full, there shouldn't be any air pressure in the air dryer to purge at these random times. Am I understanding things correctly? So now I'm wonder if I have any issue such as air seeping back through a check valve to the air dryer? Also, it would seem that the purging of air from the dryer would require an electrical signal to initiate a purge. If that's the case it would seem that the Spartan Control Module (SCM) is directing the air dryer to purge, but again why is there air to purge if there's a check valve after the air dryer.

The purging of air hasn't been a problem, as the tanks will fill once the engine is running. I'm trying to understand what's happening and if its normal or not.

 

[TJ&LadyDi]

I haven't noticed the purging once we get our 2018 MADP parked and settled, but the slow decrease in air pressure over time has occurred in both of our Newmar coaches. It appears to be quite normal.

TJ

 

[Chargerman]

The air dryer purges at a pressure level and there is not an electrical connection. It certainly should not purge with the engine off since the compressor is not running to make additional pressure. It would appear that your pressure switch/blow off valve are malfunctioning

 

[flyboy013]

The air dryer purges at a pressure level and there is not an electrical connection. It certainly should not purge with the engine off since the compressor is not running to make additional pressure. It would appear that your pressure switch/blow off valve are malfunctioning

Ok. I did a bit more research. While the air dryer does have an electrical connection (making me think that the purge may be controlled electronically), I've learned that this electrical connection is for the heater built into the air dryer.

I'm thinking that the only time there should be air in the dryer when the engine is turned off, is if the compressor was filling the tanks when the engine was turned off. That may explain why I've only heard the purging noise every so often. So if that is the case, is the dryer designed to purge that air or would it just stay in the air dryer until the engine is started again (or the air leaks out of the air dryer)?

 

[Chargerman]

It should only purge when the Max pressure of the blow off valve is reached. Should not ever purge with the engine off

 

[Ken C]

It should only purge when the Max pressure of the blow off valve is reached. Should not ever purge with the engine off

In 20+ years and 3 diesel motorhomes, 2 on Spartan, have never had a dryer purge with engine off. I think a call to Spartan would be in order.

 

[J&JD]

Could one of the drain valves on one of the air tanks possibly be bad and that is what you are hearing release? Unlikely but worth a shot pulling the release cables for each tank.

 

[flyboy013]

Could one of the drain valves on one of the air tanks possibly be bad and that is what you are hearing release? Unlikely but worth a shot pulling the release cables for each tank.

I was standing next to the compartment where the air dryer is located when I heard the air the last time, I quickly opened the compartment and I’m 99% sure that the air dryer was purging air. I may set up my camera on a tripod after my next outing and record in order to verify.

The tank valves are all up front (except for the ping tank), so it’s definitely not from the tank valves.
At this time I don’t have a problem over se. Everything seems to be working fine, I just find it odd.

 

[RKins]

Did you add something like Active Air?

 

[flyboy013]

Did you add something like Active Air?

No, but the coach has always had the Hadley equivalent.