Hey everyone, looking for some help. We had our first 70* degree day here in the mountains, and since our bodies are acclimated to -20*, i flipped on the A/C to cool down. But my heart sank when there was no cold air coming out of the vents. I switched it to "max AC" and the "regular AC" on the dial, but it seemed to make no difference. Drove a couple hours and it never came on.

 

I'm not familiar with troubleshooting AC, so where would you start? 

 

The truck had good, cold A/C last summer before the winter. Now that winter is over, the AC doesnt work. 

 

One quick side note, last year a mechanic installed and airdog and when I got the pickup back from him the AC didnt work. I let him know, and he came out and fiddled on the driver side of the engine bay for 20 seconds and fixed it. I asked what he found, and he said he forgot to reinstall a vacuum hose.... Where would this 'vacuum hose' be that he reconnected? How can I test these vacuum hoses? Is there a diagram?

 

Thanks!

I watched a couple YouTube videos and found that this little black hose feels old, maybe dry rotting? It feels like it's holding vacuum though... Any other spots to check?

Cruise control works 👍

44 minutes ago, jaredwins said:

I'm not familiar with troubleshooting AC, so where would you start? 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/54_cab-interior/basic-air-condition-repair-r485/

 

47 minutes ago, jaredwins said:

 How can I test these vacuum hoses? Is there a diagram?

If the air come out of the deforest vents when controller switched to dash or floor vent setting, then there is low, or no vacuum and the system needs to be inspected.   First check that the vacuum pump is working by placing a vacuum gauge on its suction side.  You can use a hand vacuum pump to see if the system holds vacuum.  If it doesn't hold vacuum look for detreated connectors and lines.

 

You need to be a bit more specific than "No AC"

 

For example:

 

*  Does the ventilation fan work properly on all selected speeds?

*  Is the air coming out of the vents, but just not cold air?

*  Or, is the air coming from somewhere else (such as defroster vents) and is cold?

*  Is the AC compressor cycling.

 

The vacuum supply to the HVAC selector operates various ventilation door positions to direct airflow to either the floor vents, dash vents, or defroster vents.  If the vacuum supply is removed, the default ventilation door selection will send airflow to the defroster vents only, regardless of the position of the HVAC control selector.

 

The vacuum supply has no input as to whether or not the AC compressor runs.  So, if the AC system is working properly and  if the vacuum supply was disconnected, the result would be cold air coming from the defroster vents.

 

So, check out the system and report back.

 

- John

 

 

Edited March 30, 20223 yr by Tractorman
spelling

Also you have a standard trans truck, your cruise should be electronic.

 

Need some more info about 'no A/C' like @Tractorman said. 

15 hours ago, Tractorman said:

You need to be a bit more specific than "No AC"

 

For example:

 

*  Does the ventilation fan work properly on all selected speeds?

*  Is the air coming out of the vents, but just not cold air?

*  Or, is the air coming from somewhere else (such as defroster vents) and is cold?

*  Is the AC compressor cycling.

 

The vacuum supply to the HVAC selector operates various ventilation door positions to direct airflow to either the floor vents, dash vents, or defroster vents.  If the vacuum supply is removed, the default ventilation door selection will send airflow to the defroster vents only, regardless of the position of the HVAC control selector.

 

The vacuum supply has no input as to whether or not the AC compressor runs.  So, it the AC system is working properly and  if the vacuum supply was disconnected, the result would be cold air coming from the defroster vents.

 

 

*  Does the ventilation fan work properly on all selected speeds?

Yes. If I set the selector to any position, it comes out that (and only that) vent. 

 

*  Is the air coming out of the vents, but just not cold air?

Yes. Air comes out the vents, but it's the same temp as outside temps. 

 

*  Or, is the air coming from somewhere else (such as defroster vents) and is cold?

It's never cold. Doesn't come out defroster vent unless i set it to the defroster position.

 

*  Is the AC compressor cycling.

I believe so? When I set the air to 'cold' I hear a click, and then a few seconds later another click.

Hopefully this video shows it. (shot from under the truck, passenger side, looking up). I think this is the compressor. It "clicks on" for a few seconds, then "clicks" off for ~8 seconds. Then clicks on, and off.... This process keeps repeating. 

 

 

 

 

It's the exact similar behavior as this guy on youtube. A lot of comments where just saying to refill the freon (134A) and it fixed their problem. I've seen some videos on that and it seemed simple enough. What are your thoughts on that approach?

 

 

 

 

 

Good, you answered all of the questions well.  It is likely that the refrigerant charge is low.  A rapidly cycling compressor would match the symptoms shown in your video.

 

There is nothing wrong with recharging your AC system yourself.  But, if you have never done this before, take time to watch lots of videos to get your best understanding of filling the system and the safety precautions to observe when doing so.  Wear gloves.  Liquid refrigerant vaporizes  at atmospheric pressure at around 20° below zero F. It instantly extracts the heat from of whatever it touches.

 

Also, understand that you do not know how much refrigerant or oil is currently in the system ,  Since you do not know that, it means that you do not know how much to add.  The proper way to charge an AC system is to recover the refrigerant in the system, pull a strong vacuum on the system for a determined amount of time, and then check for leaks.  If all is well, then the proper weight of refrigerant with the proper amount oil will be added to fill the system.  I only mention this because when a person decides to add refrigerant themselves, that person assumes all of the risks associated with it.

 

Before recharging, I would inspect the all of the components of the AC system that are visible for any oil residue surrounding them   A particular candidate is the AC compressor dynamic seal.  

 

Let us know what you decide.

 

- John

Typically you drain the system and pull the compressor and drain the drain out the plug in the side of the case. Now re-load with 5 to 6 ozs of PAG 100 oil. Remount and pull a vacuum on the system. Then I typically use three 12oz R134a cans. Being its leaked out I would do a o-ring seal kit and replace all o-rings. Make sure to oil the o-ring before assembly. O-ring kits are typically 20 bucks or so.