Need AC Advice

[RSchwarzli]

Sooool I rebuilt/modified my AC system on the 1990 this winter and had a friend who is in the HVAC industry charge the system. (I dont know enough to not get myself into trouble when it comes to that. )

So he charged the system and a few days later, I try AC and its not cold. Go visit him again. He agrees must not have been enough charge so we top it up. SUDDENLY, the gauges go wild and he quickly bleeds off the extra PSI. Seems the metering device was stuck and no coolant was pumping so when it suddenly cleared, there was too much pressure in the system.

So we got that sorted out and AC was good. For a few hours. Parked somewhere for 10 min (was using AC on way to destination), started truck back up, started loading the bed with stuff, and it sounded like the shops compressor started running. I didnt think anything of it. 30 sec later the front end of the truck is engulfed in smoke. Jump out of truck and shut it all down. From what I could see, it looked like the AC compressor was a bit oilier than it was before. I suspect the PSI was too high again and the emergency blow off opened.

The AC has worked for some time after that. But the weather for the last 3 weeks has been nice so didnt require AC.

Yesterday however, it was as muggy as Chewbaca's armpit. I turn the AC on. Nada. Zip. Zilch.

Thoughts?

I have only three:

1 - The metering device is stuck again. Need to check for system PSI to confirm it is not discharged by a leak

2 - Despite the system vacuum holding it PSI, I have developed a leak. System PSI check would confirm.

3 - The emergency blow off didn't seal 100% and resulted in point 2. A leak. Again PSI test will determine.



So my question is, is there anything I am missing or have not thought of?

Thanks.

Robert

 

[DVolk]

I dont know as much as my dad did , but here is a few thoughts .
1. what refrigerant was used in the system ?
2. did you use the correct oil in the compressor ?
3. Did you lubricate the O rings upon installation ?
4. Yolur freinds refrigerant did he use non contaminated refrigerant , some of the stuff out there is bad and some of the artifical stuff out there screws things up
5. Did you use any used parts such as the dryier ???

 

[RWherley]

I would check your expansion valve, like you said it could be sticking, also I have a friend who knows a lot about that stuff and he says with R134 you cant go by PSI and get an accurate charge you need to go by weight, you should use 10% less R134 then you would R22.

 

[Philip]

Robert our condensers are small for 134. I found that out a couple of weeks ago. When we were charging up my truck. We noticed high head pressures without air flow threw the condenser. Just setting a 20" box fan in front of the grille dropped head pressures 100 PSI. When you were setting there idling the head pressures went threw the roof. You most likely blew the safety valve on the compressor.

There is nothing in the expansion valve to stick or go bad. Is just a aluminum block with a plastic orifice tube in it

 

[mweiman]

Is the compressor engaging or cycling at all Robert? If so are the lines getting hot or cold? Typically with a stuck expansion valve you will see 0 or even vacuum on the low side when charging. Do you have any idea how much freon got charged into the system? I agree that it sounds like the relief valve on the compressor popped off. I will have to look at mine, not sure if a first gen had a high pressure switch of any kind that would kick the compressor out if pressure was too high.

 

[RSchwarzli]

Playing with it now.

I have boiling in the sight glass. This is what happened last time. I have a feeling that expansion valve is sticking.

The line from the cab to compressor is cool, but not cold and sveaty like it should be.



Phillip

I suspect you are right. I can't say if I remembered to turn the Horton on (still was getting into the habit) so likely got really warm and BAM!

As for the condenser, now running a Gen 2.

 

[mwilson]

Add a high pressure switch and wire it in to the fan circuit so the fan will engage on it's own like a bigga' truck when the head pressure comes up while idling or in slow traffic.

Mike.

 

[mweiman]

Robert,
I forgot about you having a horton fan.
The bubbles you are seeing in the sight glass is most likely a sign of low freon charge. A stuck closed expansion valve would not cause that, maybe if it was stuck open but doubtful. Not saying your expansion valve doesn't have an issue but most likely not the cause of the bubbles. Maybe it bled off some high pressure again at some point and you didn't notice it. I agree with Mike, you either need a high pressure switch or wire the fan to engage whenever the air is on.

 

[mwilson]

The next time you are in a bunch of traffic going slow on a hot day get up beside an 18 wheeler and listen to the fan engagement cycle. It requires almost constant fan use with the A/C on.
Cars do it too, but the electric fans sometimes have several speeds so it is not so apparent what is going on. With that Horton it is all or nothing.

Mike.

 

[RSchwarzli]

Add a high pressure switch and wire it in to the fan circuit so the fan will engage on it's own like a bigga' truck when the head pressure comes up while idling or in slow traffic.

Mike.

I cant find a switch that will work. The Horton one I have is for the newer trucks and I cant find one that fits the old Gen 1 R12 style port.

From what I have found, it was made by Texas Instruments and the R12 port style I believe model number was 20PS39-1. Have been at this for weeks looking for the info. From what I have found now, semi trucks use these however there is a zillion different head pressure engagements. So trying to determine what will be best for R12.




So followup:

I played with the truck for an hour. AC on, AC off with 5 min between.

When the AC is ON, the line coming FROM the cab that should be cold and sweaty is not even cool really.

Shut AC off.... wait 5 min. Comes back and sees expansion valve is cold and sweaty.

Turns AC on again, and then the line from the cab gets cold for about 1 min then warms up again. Also when the AC is on, I can hear what sounds like pulsating/surging air sounds inside the heater box. it does NOT sound like a leak though but hard to tell inside of a closed area. I can only assume there is a vacuum from the compressor up that line trying to suck the refrigerant and it is not allowing it past the expansion valve thus the surging when some bypasses.

Not saying any of this is right, but I think it must be the valve. Not saying I didn't lose more freon. That is always possible. I did try doing some highway runs without the fan on, with AC on, just to see if it was still cold, etc and it all seemed fine. If it vented under the truck I may not have noticed but it seems there is a LOT of air crossing the condenser so in theory as long as I am doing 75 mph it is still more airflow than a fan running at idle IMO.

 

[mwilson]

Change the expansion valve. That sounds like the same scenario that I had with a Red Dot rooftop A/C unit years ago, the expansion valve cured it.

What thread size do you need??? You may be able to find a hose end that will fit the dryer but also has a service port made to it. You could have a hose shop change the end or make up a new line. I can check with my A/C guys and find a common high pressure value between trucks to limit the choices for a switch. You could go with a two port dryer also if yours has common hose ends. Let me know what I can do to help.

Mike.

 

[mwilson]

Two brain cells just held hands long enough for me to remember "Trinary" switches...Check those out, handle both low and high pressure in one switch.
They are a Red Dot product and were used a lot in truck A/C systems before electronics.....

Mike.

 

[DVolk]

If your useing R 22 id get that out of there if your going to alternative gases for refrigerate use the Red Tek R 12 replacement

 

[RSchwarzli]

Change the expansion valve. That sounds like the same scenario that I had with a Red Dot rooftop A/C unit years ago, the expansion valve cured it.

What thread size do you need??? You may be able to find a hose end that will fit the dryer but also has a service port made to it. You could have a hose shop change the end or make up a new line. I can check with my A/C guys and find a common high pressure value between trucks to limit the choices for a switch. You could go with a two port dryer also if yours has common hose ends. Let me know what I can do to help.

Mike.

Check out page 444 and the few below it. See what I mean? LOL There is a LOT of them! I found another site at one point that had even more!

http://truckpartsetc.com/sales/PDFs/MEI/MEI_Switches.pdf

Two brain cells just held hands long enough for me to remember "Trinary" switches...Check those out, handle both low and high pressure in one switch.
They are a Red Dot product and were used a lot in truck A/C systems before electronics.....

Mike.

Mike,

Hmmmm. Those look interesting. I will do more reading on those.

 

[Bob Beauchaine]

Sounds like a problem I had right after I installed my Horton fan years ago but only in heavy traffic. I solved the problem by just turning the Horton fan on when I am in traffic and the A/C is on. Funny when I am in traffic and the A/C is on and I forget to turn the fan on it no longer does this ???

BTW how do you like the Horton fan? I have towed in 98 degree weather with it on and my temp stays at 180.

Bob

 

[Bob Beauchaine]

Sometimes it takes this old brain a little time it come up with another answer to this problem. If this is the truck that you installed the Horton fan on you might want to look at the high pressure circuit in the wiring harness. When this first happened to me I was sitting in a parking lot - hot day A/C on talking on my cellphone. Sounded just like your description - same noise. I finally got the wiring sorted out after that. You might want to take a look and see if that might help resolve your problem.

Bob

 

[RSchwarzli]

Sounds like a problem I had right after I installed my Horton fan years ago but only in heavy traffic. I solved the problem by just turning the Horton fan on when I am in traffic and the A/C is on. Funny when I am in traffic and the A/C is on and I forget to turn the fan on it no longer does this ???

BTW how do you like the Horton fan? I have towed in 98 degree weather with it on and my temp stays at 180.

Bob

Yes. I am now in the habit of fan control manually. That solves that issue I think.

LOVE the Horton. Was towing 13,000 yesterday in 95 plus high humidity and it never passed 178. NEVER seen that on this truck. I am in love with this fan!

Sometimes it takes this old brain a little time it come up with another answer to this problem. If this is the truck that you installed the Horton fan on you might want to look at the high pressure circuit in the wiring harness. When this first happened to me I was sitting in a parking lot - hot day A/C on talking on my cellphone. Sounded just like your description - same noise. I finally got the wiring sorted out after that. You might want to take a look and see if that might help resolve your problem.

Bob

Exactly. See below:


Well, here is the follow up....

I ripped my AC system apart. First thing I learnt was not much gas left in the system (Due to the bleeding out the emergency I would think) but enough that it has still been working.

I then got to the expansion valve and found the source of my second/larger issue. Seems I must have lost a drier at some point as it was 80% restricted with decadent and sludge so I can see why it was not working.

I went to NAPA and got a new H valve and got it home. Guess what? Pressure switch is tapped for the wrong side! You actually cant install it as the wiring wont plug in due to the HVAC fan being there! Unreal! How has nobody noticed this before!?

So, I went to 3 different auto parts places and inspected their valves. All the same. Wrong side. I have since located a new Mopar one so it is correct and I will be picking it up later today. I am hoping that solves all my issues finally. Would also seem I will be installed another new filter/drier just incase this one has collected **** from the system.

Damn old trucks.

 

[Philip]

I ran into the same problem when I converted my A/C to 134. The wrong expansion valve. The correct expansion valve is 3411283.

 

[RSchwarzli]

What changes in the two valves? Spring pressure?

 

[RWherley]

Where can I get one of these Horton fan hubs?