Air Dryer Again

[lamountain1976]

I am going to piggy back on the previous threads...it looks like somebody found a rock with the bottom of the air dryer. When it's cold air pressure won't climb above 30 psi, cuz I guess the water in the system is frozen and the heating element is busted off.

How do these air dryers work? Is it normal to drain a little water out of the tanks periodically? And what kind of maintenance is required?

[ThaddeusW]

I say drain the tanks daily, some say you can go a week but I wouldn't go that long. And drain them after your done driving for the day as that is when all the water is accumulated in the tanks. The air dryer might be frozen, try heating it with a heat gun (on low and held far enough away) or a hair dryer.

The air dryer cartridges should be replaced once a year and the best time is before winter.

There are three air lines going to the dryer. One is the supply port from the compressor. The second is the delivery port which runs to the wet tank and the third is a control port which signals the dryer to purge any water and oil it filtered out. The governor monitors the system pressure and controls the unloader mechanism in the compressor which "turns the compressor on". it too has three ports one hooks to the compressor, one goes to the wet tank and the third hooks to the air dryer and it can also hook to an alcohol injector.

Their operation is as follows (assuming an empty system with 0 psi):

1)The unloader mechanism in the compressor is by default closed allowing the compressor to charge the system.

2)The air from the compressor passes through the dryer and gets most of the oil and water taken out of it.

3)The tanks now start to build pressure.

4)Once the pressure reaches the governer cut out pressure (120-130PSI) the unloader line is pressurized turning off the compressor.

5)At the same time the compressor is cut off another air signal goes to the dryer to purge the water and oil.

6)once the pressure drops below 100 PSI the cycle starts again.

An electric heater coil is also used to keep the dryer from freezing. If yours is broken off then that is a definite problem. If its still there check the wires for power and then check the heater with an ohm meter. The heater is 75-90W and there should be about 1.6-2 ohms across the the heater terminals assuming the thermostat is closed from the cold (do this with the power wire disconnected).

Do you know your dryer model?

[theakerstwo]

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I say drain the tanks daily, some say you can go a week but I wouldn't go that long. And drain them after your done driving for the day as that is when all the water is accumulated in the tanks. The air dryer might be frozen, try heating it with a heat gun (on low and held far enough away) or a hair dryer.

The air dryer cartridges should be replaced once a year and the best time is before winter.

There are three air lines going to the dryer. One is the supply port from the compressor. The second is the delivery port which runs to the wet tank and the third is a control port which signals the dryer to purge any water and oil it filtered out. The governor monitors the system pressure and controls the unloader mechanism in the compressor which "turns the compressor on". it too has three ports one hooks to the compressor, one goes to the wet tank and the third hooks to the air dryer and it can also hook to an alcohol injector.

Their operation is as follows (assuming an empty system with 0 psi):

1)The unloader mechanism in the compressor is by default closed allowing the compressor to charge the system.

2)The air from the compressor passes through the dryer and gets most of the oil and water taken out of it.

3)The tanks now start to build pressure.

4)Once the pressure reaches the governer cut out pressure (120-130PSI) the unloader line is pressurized turning off the compressor.

5)At the same time the compressor is cut off another air signal goes to the dryer to purge the water and oil.

6)once the pressure drops below 100 PSI the cycle starts again.

An electric heater coil is also used to keep the dryer from freezing. If yours is broken off then that is a definite problem. If its still there check the wires for power and then check the heater with an ohm meter. The heater is 75-90W and there should be about 1.6-2 ohms across the the heater terminals assuming the thermostat is closed from the cold (do this with the power wire disconnected).

Do you know your dryer model?

If you can repair your old dier then replace it because if you live to be a 100 years old you will end up saying dont run with out a dier but if you dont repair drain ever day or ever time you get out weth 1 or 10 times a day. I have seen trans air cylinders rusted up and air fan clutchs damaged and all due to a little water in oil so i repeat repair and i think

Thaddeus told you ever thing about a air dier that that makes it work. Glenn

[lamountain1976]

I say drain the tanks daily, some say you can go a week but I wouldn't go that long. And drain them after your done driving for the day as that is when all the water is accumulated in the tanks. The air dryer might be frozen, try heating it with a heat gun (on low and held far enough away) or a hair dryer.

The air dryer cartridges should be replaced once a year and the best time is before winter.

There are three air lines going to the dryer. One is the supply port from the compressor. The second is the delivery port which runs to the wet tank and the third is a control port which signals the dryer to purge any water and oil it filtered out. The governor monitors the system pressure and controls the unloader mechanism in the compressor which "turns the compressor on". it too has three ports one hooks to the compressor, one goes to the wet tank and the third hooks to the air dryer and it can also hook to an alcohol injector.

Their operation is as follows (assuming an empty system with 0 psi):

1)The unloader mechanism in the compressor is by default closed allowing the compressor to charge the system.

2)The air from the compressor passes through the dryer and gets most of the oil and water taken out of it.

3)The tanks now start to build pressure.

4)Once the pressure reaches the governer cut out pressure (120-130PSI) the unloader line is pressurized turning off the compressor.

5)At the same time the compressor is cut off another air signal goes to the dryer to purge the water and oil.

6)once the pressure drops below 100 PSI the cycle starts again.

An electric heater coil is also used to keep the dryer from freezing. If yours is broken off then that is a definite problem. If its still there check the wires for power and then check the heater with an ohm meter. The heater is 75-90W and there should be about 1.6-2 ohms across the the heater terminals assuming the thermostat is closed from the cold (do this with the power wire disconnected).

Do you know your dryer model?

I don't know anything about it. Perhaps you can help me out. Here is a pic from the side and the bashed in underneath where the heater element must have been. What is the canister that yous suggest replacing? And how to figure out what model, in order to get correct parts?

[ThaddeusW]

That is a Bendix AD-2 dryer. Here is the service data book in PDF format from the Bexdix website:

http://www.bendixvrc.com/itemDisplay.asp?documentID=4453

It has all the information you need to service that dryer.

Another thing is I don't see the wires for the heater. Are there any wires near the dryer?

[Rob]

I spent $94.00 rebuilding my AD-2 and that included heater, switch, element, and check valve. I removed the unit from the truck and it was easy to service.

Rob

[lamountain1976]

That is a Bendix AD-2 dryer. Here is the service data book in PDF format from the Bexdix website:

http://www.bendixvrc.com/itemDisplay.asp?documentID=4453

It has all the information you need to service that dryer.

Another thing is I don't see the wires for the heater. Are there any wires near the dryer?

That is badass - thanks. There are no wires near it - I have to figure out how to wire this thing...what are your thoughts?

[lamountain1976]

I spent $94.00 rebuilding my AD-2 and that included heater, switch, element, and check valve. I removed the unit from the truck and it was easy to service.

Rob

Is that from used sources or new? Suggested leads for parts?

[ThaddeusW]

That is badass - thanks. There are no wires near it - I have to figure out how to wire this thing...what are your thoughts?

I would say hunt around a little for the wires a little just in case they were cut back or wound up and taped into a ball. There might only be one wire as the dryer might have been grounded right to the frame. If you cant find em just run a line to your fuse block and protect it with a 10 amp fuse. Then just ground the dryer heater to the frame. But make sure its a good clean connection, no rusty bolts as this will impede the flow of current.

[Rob]

I would say hunt around a little for the wires a little just in case they were cut back or wound up and taped into a ball. There might only be one wire as the dryer might have been grounded right to the frame. If you cant find em just run a line to your fuse block and protect it with a 10 amp fuse. Then just ground the dryer heater to the frame. But make sure its a good clean connection, no rusty bolts as this will impede the flow of current.

Thad, if you do that, anytime the temperature is below 32-35 degrees the heater will energize. The power wire only needs to be hot when the ignition key is in the "on" position. I know that is what you meant though. I make the same type of mistakes quite often!

My air dryer was rebuilt with all new parts with the exception of the cartridge which is rebuilt. Any truck parts supplier will be able to help you with parts as this was a common dryer.

Rob

[ThaddeusW]

Thad, if you do that, anytime the temperature is below 32-35 degrees the heater will energize. The power wire only needs to be hot when the ignition key is in the "on" position. I know that is what you meant though. I make the same type of mistakes quite often!

My air dryer was rebuilt with all new parts with the exception of the cartridge which is rebuilt. Any truck parts supplier will be able to help you with parts as this was a common dryer.

Rob

Rob,

Your right I did mean that but I should have been more clear and said an ignition switched feed.

[lamountain1976]

Rob,

Your right I did mean that but I should have been more clear and said an ignition switched feed.

The bottom of the dryer was all mashed in and no wires to be found. I sprung for a remanufactured canister. Just traded in the core.

Two questions: first, what was the consensus? One wire to the ingnition thru the fuse block and one ground to the frame? And second, some of you commented on oil being pushed on by the compressor. Can you elaborate? I mean, so the compressor is lubricated with engine oil, and some seals are bad or something and the oil is leaking into the air system? Also, how would one tell if this is happening? How serious a problem is this? And how is it fixed?

[theakerstwo]

The bottom of the dryer was all mashed in and no wires to be found. I sprung for a remanufactured canister. Just traded in the core.

Two questions: first, what was the consensus? One wire to the ingnition thru the fuse block and one ground to the frame? And second, some of you commented on oil being pushed on by the compressor. Can you elaborate? I mean, so the compressor is lubricated with engine oil, and some seals are bad or something and the oil is leaking into the air system? Also, how would one tell if this is happening? How serious a problem is this? And how is it fixed?

The way you can tell if your compressor is pumping oil is to watch the air died discharge its exhaust on the ground under it and there should not be any oil on the ground. If so then change the compressor because the oil in the air will cause the dier not to work and on top of ever thing else oil in the air will cause problems to all air valve in the air system. glenn

[lamountain1976]

Okay good to know. I will have a look at it. Would you replace the compressor or can it be rebuilt?

[ThaddeusW]

Okay good to know. I will have a look at it. Would you replace the compressor or can it be rebuilt?

It can be rebuilt. You have to most likely replace the head gasket and rings. Once you know the model you can then order a rebuild kit. Its probably a Bendix thu-flow 500 or 700. There is a tag right on the side of the compressor.