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HALDEX AIR DRYER GOVERNOR ADJUSTMENT
I just replaced the Haldex air dryer and the new one is set with a 135 PSI cutout. I don’t need or want that much. The governor adjustment is under a rubber boot, but since I am going to have to adjust, climb out of the pit, start the bus, check pressures, and if not correct repeat until I get it right, I am seeking knowledge.
Does anyone know what direction to turn the adjusting screw, and how much turns or fractions of a turn drop it down approximately 15 PSI?
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7 Replies
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I’m familiar with Bendix, 1/4 turn is 4lbs
Clockwise increase
Counter clockwise decrease
Later
bv
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Thanks. Haldex rep reached out and gave me a phone number. I will call this afternoon and post.
This is on the Haldex dryers now used by Prevost and has the integral governor.
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I wouldn’t mess with it. All three of my coaches have been at 135 +/- a pound or two. Doesn’t seem to be an issue…..
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Mark, I am an advocate of trying to avoid self inflicted wounds, and all previous coaches and governors were 120 PSI from the factory.
At one time we had some pneumatic devices with 130 PSI limitations.
Haldex confirmed Prevost is now ordering 135 PSI dryers (my original was 120) and the technician confirmed what Bernie said about counter clockwise and doing 1/4 turn increments, having no issue with my resetting it to the original pressures.
One of my primary concerns is unique to my driveway. I have to fully raise the front prior to going across the breakover at the top just before my garage. My air bags are limited to 100 PSI (printed right on the air bag) so I am an have been using full system pressure to extend my air bags, and while I am not happy with 120, so far, so good, but now at 135 I am not so comfortable.
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Just a follow up comment. The way Prevost has installed Haldex dryers making any adjustments to the governor pressure isn’t easy because of tight space at the back of the dryer where the adjusting screw is.
To get more room I just removed the 3 mounting bolts and because of all the flexible hose lines I can pull the dryer away from the bulkhead to easily put an allen wrench in the adjusting screw.
But 1/4 turn is going to make a relatively small adjustment in pressure so to minimize trips down the pit to make an adjustment, then back up to the driver’s seat to see how I did after bleeding off brake system pressure and allowing it to build back up I am going to make aggressive adjustments and may do my next adjustment at one full turn.
Counter clockwise does reduce cut out pressure.
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Good Morning Jon,
I am going back and reading all posts regarding air dryers and am curious why you replaced your Haldex air dryer…
Was it purely preventative maintenance? Or was there an issue?
Was there sufficient slack in the air tubing to make connecting them easy or was it a significant challenge?
Were you able to re-use the same fittings?
Thinking of changing mine as preventative maintenance…replacement tips appreciated 🙂
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My original dryer was OK, but more than one owner with a similar vintage to my coach mentioned an issue with the purge valve not closing and an inability to build air.
That dryer cannot even be reached unless you can somehow get under the coach, and with no air the coach is not going to be able to be raised so rather than take a chance I replaced the dryer with all my Norgrens at the same time. Hose lengths were no issue, and I used that opportunity to replace all the original push in fittings with compression fittings. I still have the original dryer and it is in good working condition, but at the time of removal it was 13 or 14 years old.
There are a number of us on here that are inclined to replace perfectly good working parts “just in case”.
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