AD-9 Finally Purging!!

[Stormcloud]

Hmmm..

Brand new AD-9 air dryer being installed on my MCI 7. Builds air just fine, but won't purge.
The mechanic tried with bus air at 130lbs and shop air at 150 lbs; 'trigger' line from the new governor dumps some air when the compressor hits 130lbs, but the dryer won't dump. We re-checked the routing of the air lines...it's all correct.

He figures its a faulty dump valve (even though its new). He will install a new valve tomorrow. This dryer came from a rebuilder in the USA that assembles them from new component parts. Any warranty issue would take a couple of weeks to resolve, or I would just insist on a replacement.

Any other suggestions?

Thanks.

Mark

[Dreamscape]

Hi Mark,

I just installed one on my Eagle 01 a week ago and have good results.

My compressor cuts off at 120# and the AD-9 sneezes at that point. At what point did the compressor cut off before you installed the drier?

Out of curriosity, where is the 1/4" line from the drier to the govenor going to on the govenor? It is going to the unload side, correct? I know you said all lines were correct, just trying to verify.

Good Luck,

Paul

[buswarrior]

Re: checking the lines...

The labeling of the ports on air valves have been known to fool folks.

Be sure that the DEL, SUP, EXH, 1, 2, or whatever, are plumbed and plugged the way Bendix and friends intended, not the way that "makes sence".

Sometimes the delivery is really the supply, and the exhaust is for using on an oil rig combine...from the pneumatic engineering perspective.

Otherwise, rule out the governor: compressor cut-in, no pressure in the signal line, cut-out, signal line at tank pressure, ok? then blame the new air drier valving.

happy coaching!
buswarrior

[lloyd]

I would try putting shop air to the purge line on the air dryer and see if it purges then. If it does then it is a problem with the governor to the air dryer. If it does not purge then it is an air dryer problem. Also the air governor should not leak air out of the exhaust port when cutting out the compressor, only when the compressor cuts back in.
Lloyd

[Stormcloud]

Still troubles.

The governor was replaced with one that has more ports (?). The small line that goes from the governor to the AD9 (signal line) has so little pressure/volume of air that Al can put his thumb over the end of the line to stop the air.
The compressor builds air just fine, but with the new governor the air builds to close to 140psi.....thought maybe a bad governor, so it was exchanged for another; no change. With the old governor, the air builds to around 125psi and stops.

Should a new governor(s) require adjustment?

Once air is built up, the drier will 'sneeze' if you put the blowgun at the trigger line where it enters the dryer.
Al (the mechanic) thought there may be a regulator in the small line that returns from the wet tank to the governor, limiting the air available to the governor??
It all points to either two defective governors, or incorrect line connection? He's double checked the routing of the lines.
Any other ideas?

I'll be taking all this info back to the mechanic early tomorrow AM

Thanks again for your help!!!

Mark

[Sojourner]

Stormcloud...I would suggest to purchase enough 1/4" DOT nylon tubing with "push-on" fittings. Temporary hook up to both taps to bypass the old governor signal line for testing. If it works then install it for permanent installation. It could be either pinch or rusted pin hole in line.

Let us know what happen. Thanks

FWIW

Sojourn for Christ, Gerald

[Dreamscape]

You can also adjust the govenor cut out and cut in pressure, mine is set to around 90 lbs and 120 lbs. When you install a new govenor it may have to be adjusted for your requirements, I had to adjust mine when I installed a brand new one.

The air line from the drier to the govenor should be to the unload port on the govenor, take out a plug and install it there.

You have to have a blockage if the air pressure is so little that you put your finger over it to stop the air flow.

Good Luck,

Paul

[buswarrior]

For the clarification of readers of this thread who are still learning, technically, the governor for the air compressor has one adjustment, which sets the cut-out pressure.

Cut-in will be approximately 20 to 25 lbs below whatever you set cut-out at. That range is not adjustable.

Otherwise, good info here, let's see what we may learn from the next report!!!

happy coaching!
buswarrior

[Dreamscape]

Good Catch BW! My goof!

Paul

[buswarrior]

Hey, we're all in this together!

keep your stick on the ice.

happy coaching!
buswarrior

[Stormcloud]

FINALLY...the air dryer is working as it should.

First, the AD9 unit (new) arrived with a stuck purge valve. Al (the mechanic) thought it may have been sitting a long time on the shelf?!?
He cleaned the valve and reassembled it.

Next the unit wouldn't purge, unless shop air was introduced into the trigger fitting on the air dryer.
Al thought maybe it was a defective governor, as he had to replace the governor to get additional port to operate the dryer.
So he exchanged the D-2 governor for another new one.

No change. The dryer wouldn't purge.

Bypassed the air line from the wet tank to the governor with a temporary line. Still no purge.

Everything pointed to the governor. He removed the second new governor and found a stuck plunger!
Cleaned, greased and reassembled and it works exactly like it should.

The parts supplier was notified of the 'defective' governor. Don't know how many more they will find, but
Al said a few years back, the entire shipment of D-2 governors to their shop (~50) were all defective.

Thanks all for the advice...I certainly appreciate it.

While the bus was in the shop, I had him install and air line off the tag axle regulator to the rear bumper
where there is a now a quick connect fitting....also a shutoff valve was installed so that the integrity of the air system
isn't solely dependant on the quick-disconnect.

I will be installing an air cylinder to operate the brake pedal on the toad (Chevy Tracker) similar to Fred Hobe's suggestion.
I'll also be installing a breakaway valve and airtank, just in case.

Thanks again!.

Mark

[Sojourner]

Thanks so much for sharing your hard learned run around to get it fix. I appreciate your this report.

It always possible for any new or rebuild part to be defective.

We try to do our best using key stroke, assuming with new parts it is OK but might be its the problem.

I always try purchase new idem...no rebuild unless a large ticket idem such as engine and transmission.

Again thanks for informed us.

Sojourn for Christ, Gerald

[buswarrior]

thanks for closing the thread off with your report of success!

happy coaching!
buswarrior