Air dryer freeze up and other problems

[BenRoberts]

ok I have an up date here are my findings. Truck had 25v in the battery, started just fine. truck was charging right around 25v running with lights and what not on 24.7v. with a meter on it the volt gauge read high then low then normal with no change on the meter. It also started building too much air pressure again and the horn and wipers did not function during this condition

 

[74M35A2]

It is not charging. 25.6V is standard voltage for full charged batteries in good condition. Anything over 25.6V is charging.

 

[doghead]

PPV is frozen or stuck.

 

[BenRoberts]

This truck is a weapon of mass bankruption. lots of parts on the way

 

[Tinstar]

Like they say.....

All it takes is Money

 

[gimpyrobb]

Did you try adjusting the alt voltage output? They have a potentiometer for that.

 

[BenRoberts]

Did you try adjusting the alt voltage output? They have a potentiometer for that.

I did not. Was not aware this could happen. I will search a write up on that

 

[porkysplace]

This truck is a weapon of mass bankruption. lots of parts on the way

Purchase of the truck is the cheapest part of owning it.

 

[Andrmorr]

Is the PPV serviceable?

 

[porkysplace]

Is the PPV serviceable?

Eriks has new ones for $27 , probably not worth even trying to rebuild.

 

[74M35A2]

Low cost replacement part @ NAPA.

Volt adjust screw is under an Allen head cover screw by the wire connection cover area if I remember right.

 

[Andrmorr]

Eriks has new ones for $27 , probably not worth even trying to rebuild.

Thinking more along the line of periodic maintenance keeping it functional so it doesn't fail...

 

[porkysplace]

Thinking more along the line of periodic maintenance keeping it functional so it doesn't fail...

Keeping moisture out of the air system is the key maintenance you can do to prevent failure.

 

[Andrmorr]

Keeping moisture out of the air system is the key maintenance you can do to prevent failure.

Speaking of that...where is the best place to insert anti freeze into a M939 air system...what kind, and how much is recommended...

 

[porkysplace]

Speaking of that...where is the best place to insert anti freeze into a M939 air system...what kind, and how much is recommended...

The main line off the compressor is the best place to get it into the system . But this is one of those subjects the is up for debate as the anti-freeze can damage the air dryer and other parts of the system according to some reports. keeping the air dryer serviced and the tanks drained daily is the best method.

 

[BenRoberts]

I bought the ppv at Erik's last night. I did find cheaper ones but I like doing business there. I'm supposed to get a bunch of ice here tonight and tomorrow but once it thaws I will try that voltage adjustment

 

[Suprman]

If the voltage is high its usually the regulator thats bad. Its on the back and of the alternator and can be replaced without removing the alternator. There are 2 different types and they are not interchangeable. Alternators that say hellas greece and then everything else.

 

[74M35A2]

Your truck should have abs, and therefore an air dryer by the mid axle. I serviced mine once, and I have not drained a single drop of water from any drain after. I actually gave up on opening them because it seems to be 100% effective. Everybody will tell me that is terrible, and that is fine. I will change cartridges on it again this spring.

 

[Tinstar]

I bought the ppv at Erik's last night. I did find cheaper ones but I like doing business there. I'm supposed to get a bunch of ice here tonight and tomorrow but once it thaws I will try that voltage adjustment

Highly recommend to ditch the stock alternator asap.

When mine went bad, it was instant.
Took out PCB and ABS module.
CTIS controller hasn't acted same since, so count that too.

I coukd have bought three new Delco-Remy alternators for what its
cost me to replace what the lousy stock alternator fried.

I too thought since mines working fine, why replace it.
Yea....hindsight is 20/20

 

[simp5782]

Speaking of that...where is the best place to insert anti freeze into a M939 air system...what kind, and how much is recommended...

1/2 a quart. Take the line off the wet tank and add it in there. That way it will circulate. You can put some on the charging line going into the air dryer but do not use a lot. The dryer will just soak it up and not let it circulate. The wet tank holds most of the crap in the system.



The alternators on these trucks are hit or miss on being junk. I have done 32,000miles in 6 months. Never blew an alternator, pcb, or abs module. It is the luck of the draw really.

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