AC troubleshooting

[tophat36]

I’m curious the best way to start assessing the health of the ac system I have. This is a factory AC, doesn’t have a belt installed currently. Should I start there and install a belt? Is there a way to check if the compressor works? The guy I bought it from never even tried it, 20 years and didn’t even try lol! So he wasn’t sure if it ever worked. Just looking for clues to see if this system could be recharged as is. Also sounds like there would need to be a conversion to get it charged w modern refrigerant.

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[Clovis]

Try and turn the pulley and clutch by hand if they turn put the belt see what happens. Maybe check to make sure the compressor still has oil. The 134r conversation is easy the adapters screw right into the ports already there. Check to make sure it will hold vacuum before you add refrigerant.

 

[Trucksareforwork]

I rebuilt the system on my 85 a year or so ago. A few big things from memory:

1. If the system is open at all plan to flush out the lines, condenser, evaporator. This isn’t hard it just takes some time and an air compressor. I bought a cheap flush tank that worked w my compressor.

2. As was said, check to see if the compressor rotates. In my situation, the compressor did turn but had a bearing seal leak and so I replaced it. They are rebuildable for the patient types. A lot of people switch to the sanden compressors but I didn’t want to mess with new brackets. I had an r4 style compressor and just bought a new one.

3. You might consider checking whether all the equipment is intact in the dash as well. I was lucky. Didn’t have to go search for missing parts.

4. Replace the orifice tube and all o rings and ensure the system will seal up. There aren’t a ton of them, but old ones get compressed and will leak.

5. Once the system is together, be sure to pull a vacuum for an hour and then close the system to test whether it leaks down. You want no leaks.

6. Then, if all checks out, you can have the system charged with the proper amount of oil and 134a. As mentioned; this requires changes to the nozzles, but isn’t all that hard to do on your own.

Mine was done a last year and cools like a champ today. A by product was that I bought gauges and a vacuum pump, and even with the cost of a new compressor was well under the cost of having the system rebuilt or modernized. I have used the gauges and pump on my sons truck to fix the ac, and so having the tools made me a hero too.

 

[tophat36]

I rebuilt the system on my 85 a year or so ago. A few big things from memory:

1. If the system is open at all plan to flush out the lines, condenser, evaporator. This isn’t hard it just takes some time and an air compressor. I bought a cheap flush tank that worked w my compressor.

2. As was said, check to see if the compressor rotates. In my situation, the compressor did turn but had a bearing seal leak and so I replaced it. They are rebuildable for the patient types. A lot of people switch to the sanden compressors but I didn’t want to mess with new brackets. I had an r4 style compressor and just bought a new one.

3. You might consider checking whether all the equipment is intact in the dash as well. I was lucky. Didn’t have to go search for missing parts.

4. Replace the orifice tube and all o rings and ensure the system will seal up. There aren’t a ton of them, but old ones get compressed and will leak.

5. Once the system is together, be sure to pull a vacuum for an hour and then close the system to test whether it leaks down. You want no leaks.

6. Then, if all checks out, you can have the system charged with the proper amount of oil and 134a. As mentioned; this requires changes to the nozzles, but isn’t all that hard to do on your own.

Mine was done a last year and cools like a champ today. A by product was that I bought gauges and a vacuum pump, and even with the cost of a new compressor was well under the cost of having the system rebuilt or modernized. I have used the gauges and pump on my sons truck to fix the ac, and so having the tools made me a hero too.

How’d you figure all that out? Any good references you can recommend? I’m all for investing in the tools, have a compressor so I’m good there. What could be missing in the cab? Literally nothing has been messed with on this truck other than the radio and speakers. Pretty sure it’s all there. Pretty sure the compressor spins but should 2 things turn?

 

[fast 99]

Pully will spin with the belts and should not have any roughness. On compressor front try to turn the clutch hub. Should not be stuck to the pully or frozen. If it is, clutch or compressor is bad. Although there are replacement clutch parts available buy a reman compressor assy
w/clutch.

My experience with dead systems like yours isn't good. Many times, the entire system needs replacement, o haul and/or repair. But I do it for customers and have to guarantee it.

Good luck

 

[Trucksareforwork]

How’d you figure all that out? Any good references you can recommend? I’m all for investing in the tools, have a compressor so I’m good there. What could be missing in the cab? Literally nothing has been messed with on this truck other than the radio and speakers. Pretty sure it’s all there. Pretty sure the compressor spins but should 2 things turn?

I did a lot of homework on the system while figuring it out, then just read a lot of posts and watched a few youtubes on best ways to suction and charge the system. Biggest issue I can imagine in the cab would be rotten vacuum tubes (both in the cab and in the engine bay). They get brittle.

It's like a lot of things on these trucks, once you invest a little time to understand how they work, it's not that intimidating to work on them. I actually only just last month rebuilt the back drums on another square I have, and what looked like a complete rube goldberg contraption to me before doing so actually makes a lot of sense afterward. The first one probably took me more than an hour, the second one maybe half an hour (starting from drums off).

Back to your A/C: I would first just make sure all the components are intact. If they are, then I would flush the system. This is the pressure pot I used: https://www.amazon.com/gp/product/B07T7MZ8L5/

I would then reassemble with new o rings and orifice tube. They say use the blue one. Maybe 12 - 15 dollars total at this point.

Then, I might look for a place I could rent a set of manifold gauges and vacuum pump (or a friend with one). You can buy them pretty cheap on HF or AMZN but you start to get committed at that time. You want to pull a vacuum down to near 30 inches of mercury for an hour or so, then close off the valves and come back in a few hours to see if the system holds the vacuum.

If you have a system that holds vacuum, then you need to see if, when you charge it, your compressor is going. That probably costs you 25 bucks worth of 134a to test. Have to have the manifold gauges and a can tap valve to do this.

If your refrigerant system holds refrigerant, your compressor engages, and your internal switches work, then you should be in good shape.

That's easy for me to say... I probably worked on it for a few hours per weekend over the course of a month to get it right, starting from zero auto AC work experience.

Here are the vids from my youtube history (not saying they are the only ones, but they are the ones I must have watched):

How to flush:

xc_hide_links_from_guests_guests_error_hide_media

Orifice tube replacement:

xc_hide_links_from_guests_guests_error_hide_media

Series on condenser replacement:

xc_hide_links_from_guests_guests_error_hide_media

Schrader valve replacement:

xc_hide_links_from_guests_guests_error_hide_media

Leak testing:

xc_hide_links_from_guests_guests_error_hide_media

Evaporator core service and replacement (I didn't do this): https://youtu.be/M4hGULHGo6U
Compressor Clutch Replacement (I did this because I rebult my old compressor after the fact): https://youtu.be/URqFd3KkSRY
How to vacuum and recharge your system: https://youtu.be/4EqdrBVb0sY

Those should get you started.

 

[Bextreme04]

You have almost the same truck as me. I just got my AC back up and running for the second time. As others have said, see if the pulley will free spin(the part the belt goes on) and then see if you can grab the front part of the compressor and have it turn with some resistance. If it does, you might have a functional system that just lost a belt many many years ago. You have an A6 compressor, so you would need to fully disassemble the entire system and the compressor, flush everything thoroughly to remove the old mineral oil, then replace all of the O-rings and rubber with R134 compatible ones, replace the filter/dryer and orifice tube, install conversion fittings, then vacuum the whole system and charge with about 3 12oz cans of R134.

Doing anything with the original R12 system is going to be prohibitively expensive. Your only option if ANYTHING on it is not functioning properly is to convert the whole thing over to R134.

I'm still using all of my original main components. I did buy a new main manifold/hose assembly, flushed everything, replaced the filter/dryer and orings, installed a new blue orifice tube, and rebuilt the old A6 compressor with R134 compatible rubber. I flushed all the old mineral oil out while the compressor was apart and then filled it with ~10oz of PAG 150 oil. The A6 compressors have an internal oil reservoir that pumps oil up into the refrigerant, so no need to put oil in any other parts of the system.

The reason I had to get the system going twice was because I didn't rebuild the old compressor the first time I got it going. It also had the AC belt off and had all the lines connected, but no charge. I replaced all the orings, orifice tube, filter/dryer, pressure switch, and put on the conversion fittings and had flushed as much oil out of the compressor as I could, then filled with PAG and charged it. It worked great for about 6 months and then blew out the old carbon seal on the compressor shaft(this is a known weakness on the A6 compressors). So just a few weeks ago I finally bought a rebuild kit on ebay for ~$30 and took the compressor apart to fix it. The hardest part was renting all of the special tools to pull the old compressor clutch off the front. You need a few special snap ring pliers and some patience to get the snap rings off and then a special puller to get the clutch and stator off the front of the housing. Once that is done, it is fairly simple to rebuild. The newer rebuild kits come with a modern rubber double lip seal for the compressor that is R134 compatible and will keep oil/refrigerant from leaking out of the shaft like the old carbon/ceramic one did.

 

[tophat36]

I did a lot of homework on the system while figuring it out, then just read a lot of posts and watched a few youtubes on best ways to suction and charge the system. Biggest issue I can imagine in the cab would be rotten vacuum tubes (both in the cab and in the engine bay). They get brittle.

It's like a lot of things on these trucks, once you invest a little time to understand how they work, it's not that intimidating to work on them. I actually only just last month rebuilt the back drums on another square I have, and what looked like a complete rube goldberg contraption to me before doing so actually makes a lot of sense afterward. The first one probably took me more than an hour, the second one maybe half an hour (starting from drums off).

Back to your A/C: I would first just make sure all the components are intact. If they are, then I would flush the system. This is the pressure pot I used: https://www.amazon.com/gp/product/B07T7MZ8L5/

I would then reassemble with new o rings and orifice tube. They say use the blue one. Maybe 12 - 15 dollars total at this point.

Then, I might look for a place I could rent a set of manifold gauges and vacuum pump (or a friend with one). You can buy them pretty cheap on HF or AMZN but you start to get committed at that time. You want to pull a vacuum down to near 30 inches of mercury for an hour or so, then close off the valves and come back in a few hours to see if the system holds the vacuum.

If you have a system that holds vacuum, then you need to see if, when you charge it, your compressor is going. That probably costs you 25 bucks worth of 134a to test. Have to have the manifold gauges and a can tap valve to do this.

If your refrigerant system holds refrigerant, your compressor engages, and your internal switches work, then you should be in good shape.

That's easy for me to say... I probably worked on it for a few hours per weekend over the course of a month to get it right, starting from zero auto AC work experience.

Here are the vids from my youtube history (not saying they are the only ones, but they are the ones I must have watched):

How to flush:

xc_hide_links_from_guests_guests_error_hide_media

Orifice tube replacement:

xc_hide_links_from_guests_guests_error_hide_media

Series on condenser replacement:

xc_hide_links_from_guests_guests_error_hide_media

Schrader valve replacement:

xc_hide_links_from_guests_guests_error_hide_media

Leak testing:

xc_hide_links_from_guests_guests_error_hide_media

Evaporator core service and replacement (I didn't do this): https://youtu.be/M4hGULHGo6U
Compressor Clutch Replacement (I did this because I rebult my old compressor after the fact): https://youtu.be/URqFd3KkSRY
How to vacuum and recharge your system: https://youtu.be/4EqdrBVb0sY

Those should get you started.

Um wow! That’s some seriously helpful info, can’t thank you enough…going to be buying or borrowing some tools when I get a chance to get to this.

 

[tophat36]

You have almost the same truck as me. I just got my AC back up and running for the second time. As others have said, see if the pulley will free spin(the part the belt goes on) and then see if you can grab the front part of the compressor and have it turn with some resistance. If it does, you might have a functional system that just lost a belt many many years ago. You have an A6 compressor, so you would need to fully disassemble the entire system and the compressor, flush everything thoroughly to remove the old mineral oil, then replace all of the O-rings and rubber with R134 compatible ones, replace the filter/dryer and orifice tube, install conversion fittings, then vacuum the whole system and charge with about 3 12oz cans of R134.

Doing anything with the original R12 system is going to be prohibitively expensive. Your only option if ANYTHING on it is not functioning properly is to convert the whole thing over to R134.

I'm still using all of my original main components. I did buy a new main manifold/hose assembly, flushed everything, replaced the filter/dryer and orings, installed a new blue orifice tube, and rebuilt the old A6 compressor with R134 compatible rubber. I flushed all the old mineral oil out while the compressor was apart and then filled it with ~10oz of PAG 150 oil. The A6 compressors have an internal oil reservoir that pumps oil up into the refrigerant, so no need to put oil in any other parts of the system.

The reason I had to get the system going twice was because I didn't rebuild the old compressor the first time I got it going. It also had the AC belt off and had all the lines connected, but no charge. I replaced all the orings, orifice tube, filter/dryer, pressure switch, and put on the conversion fittings and had flushed as much oil out of the compressor as I could, then filled with PAG and charged it. It worked great for about 6 months and then blew out the old carbon seal on the compressor shaft(this is a known weakness on the A6 compressors). So just a few weeks ago I finally bought a rebuild kit on ebay for ~$30 and took the compressor apart to fix it. The hardest part was renting all of the special tools to pull the old compressor clutch off the front. You need a few special snap ring pliers and some patience to get the snap rings off and then a special puller to get the clutch and stator off the front of the housing. Once that is done, it is fairly simple to rebuild. The newer rebuild kits come with a modern rubber double lip seal for the compressor that is R134 compatible and will keep oil/refrigerant from leaking out of the shaft like the old carbon/ceramic one did.

Oh right on, what kinda truck do you have?! Well I just went and checked, the pulley part def turns and the front part also turns with some resistance but both def turn, so I guess that’s a good first step. What does something like this cost if I don’t have anything major to replace? Thank you !

 

[Trucksareforwork]

Um wow! That’s some seriously helpful info, can’t thank you enough…going to be buying or borrowing some tools when I get a chance to get to this.

yeah, I did forget the part about replacing the accumulator / filter dryer. You have to do that if the system has been open. It's a piece of cake to replace but is a bit more expense (30 bucks or so IIRC).

 

[Bextreme04]

Oh right on, what kinda truck do you have?! Well I just went and checked, the pulley part def turns and the front part also turns with some resistance but both def turn, so I guess that’s a good first step. What does something like this cost if I don’t have anything major to replace? Thank you !

I have a 1980 GMC Sierra Classic K25 pickup(its the one in my profile pic). Its the 8600GVW option, so federal heavy duty truck emissions(no cat, no EGR).

Honestly, cost wise, it is going to be mostly labor cost. A shop like @SirRobyn0 is going to be your best bet because they have the experience to know what it takes time-wise to do the conversion. Parts are cheap. You can get an o-ring kit, filter dryer, compressor rebuild kit, pressure switch, and belt for probably ~$100 all-in. Its likely to take 2-3 days of shop time to do all of the disassembly, rebuild, cleaning, reassembly, vacuum/testing, and charging. R134 is gonna be another $40 to fill the whole system.

AC techs are real proud of their skills and shops charge a fortune for what they are actually doing for any AC work. I learned in the Army when deployed in Iraq and when I got out I had some more specific AC training as a field service rep Oshkosh Defense. All of the armored vehicles overseas have AC systems and they get to be big ovens(you can see 160 degree temps or more inside them) when the stuff isn't working, so having a broken AC system will make a vehicle unable to be used.

I just bought a cheap manifold/vacuum kit from Amazon for ~$100 about 7 years ago and it is still going strong. I have used it on at least four of my vehicles several times and used it to install a mini-split AC unit in my shop a few years ago. It has easily paid for itself multiple times. You can rent the same equipment from your local autozone for free as well as a AC flush kit that uses solvent and an air compressor connection.

 

[SirRobyn0]

@Bextreme04 Thanks for bringing me into this thread. @tophat36 Yes, I'd be more than happy to look at this problem at the shop as well, however Eric is right shops do tend to charge a lot for A/C work. It's not all fluff though there are a lot of costs, and to some degree a shop has more to protect than you do. The biggest thing that prevents a proper DIY job is the inability to recover refrigerant, and to charge properly. Back in the old days it was much easier for someone with experience to guess a close charge with pressures with pressures alone. R-134A is much harder to get correctly off pressure. If the system does need to be opened up, retro-fit it to R134A, R12 is still out there in limited quantities but is SUPER expensive. It's not like this is Arizona. My 84 C20 has been retrofitted since I bought it 6 years ago and it does plenty good enough for our temps around here.

So you have gotten tons of good advice. But start with the basics. See if the compressor clutch and the pully turn ok and without a ton of play. If that looks good put a belt on it and see what happens. Then you can with advice from us decide if you want to dive into it, doing all the work or some of the work letting a shop do things like the actual refrigerant handling, or what avenue you'd like to go down.

SRO

 

[tophat36]

I have a 1980 GMC Sierra Classic K25 pickup(its the one in my profile pic). Its the 8600GVW option, so federal heavy duty truck emissions(no cat, no EGR).

Honestly, cost wise, it is going to be mostly labor cost. A shop like @SirRobyn0 is going to be your best bet because they have the experience to know what it takes time-wise to do the conversion. Parts are cheap. You can get an o-ring kit, filter dryer, compressor rebuild kit, pressure switch, and belt for probably ~$100 all-in. Its likely to take 2-3 days of shop time to do all of the disassembly, rebuild, cleaning, reassembly, vacuum/testing, and charging. R134 is gonna be another $40 to fill the whole system.

AC techs are real proud of their skills and shops charge a fortune for what they are actually doing for any AC work. I learned in the Army when deployed in Iraq and when I got out I had some more specific AC training as a field service rep Oshkosh Defense. All of the armored vehicles overseas have AC systems and they get to be big ovens(you can see 160 degree temps or more inside them) when the stuff isn't working, so having a broken AC system will make a vehicle unable to be used.

I just bought a cheap manifold/vacuum kit from Amazon for ~$100 about 7 years ago and it is still going strong. I have used it on at least four of my vehicles several times and used it to install a mini-split AC unit in my shop a few years ago. It has easily paid for itself multiple times. You can rent the same equipment from your local autozone for free as well as a AC flush kit that uses solvent and an air compressor connection.

I also have the 8600 gvw, does that mean mine didn’t come with the cat standard also? I feel like mine has the EGR though, it has all of the emissions things installed still. Ideally I want to do all the work I can with the exception of refrigerant handling, as that’s mostly the point of this truck for me so I can learn these things. I think investing in the tools will make sense long term, considering I spent $300 on the spring compressor alone when doing front end, all of that seems much more reasonable. The awesome guy who handles all my hvac at my rental learned his stuff in the army as well and is super knowledgeable, so I’m sure you are too! Thank you for all of the advice.

 

[tophat36]

@Bextreme04 Thanks for bringing me into this thread. @tophat36 Yes, I'd be more than happy to look at this problem at the shop as well, however Eric is right shops do tend to charge a lot for A/C work. It's not all fluff though there are a lot of costs, and to some degree a shop has more to protect than you do. The biggest thing that prevents a proper DIY job is the inability to recover refrigerant, and to charge properly. Back in the old days it was much easier for someone with experience to guess a close charge with pressures with pressures alone. R-134A is much harder to get correctly off pressure. If the system does need to be opened up, retro-fit it to R134A, R12 is still out there in limited quantities but is SUPER expensive. It's not like this is Arizona. My 84 C20 has been retrofitted since I bought it 6 years ago and it does plenty good enough for our temps around here.

So you have gotten tons of good advice. But start with the basics. See if the compressor clutch and the pully turn ok and without a ton of play. If that looks good put a belt on it and see what happens. Then you can with advice from us decide if you want to dive into it, doing all the work or some of the work letting a shop do things like the actual refrigerant handling, or what avenue you'd like to go down.

SRO

@Bextreme04 Thanks for bringing me into this thread. @tophat36 Yes, I'd be more than happy to look at this problem at the shop as well, however Eric is right shops do tend to charge a lot for A/C work. It's not all fluff though there are a lot of costs, and to some degree a shop has more to protect than you do. The biggest thing that prevents a proper DIY job is the inability to recover refrigerant, and to charge properly. Back in the old days it was much easier for someone with experience to guess a close charge with pressures with pressures alone. R-134A is much harder to get correctly off pressure. If the system does need to be opened up, retro-fit it to R134A, R12 is still out there in limited quantities but is SUPER expensive. It's not like this is Arizona. My 84 C20 has been retrofitted since I bought it 6 years ago and it does plenty good enough for our temps around here.

So you have gotten tons of good advice. But start with the basics. See if the compressor clutch and the pully turn ok and without a ton of play. If that looks good put a belt on it and see what happens. Then you can with advice from us decide if you want to dive into it, doing all the work or some of the work letting a shop do things like the actual refrigerant handling, or what avenue you'd like to go down.

SRO

Thanks @SirRobyn0, I think that’s what I was thinking to do, just get the belt on and go from there.

 

[Bextreme04]

I also have the 8600 gvw, does that mean mine didn’t come with the cat standard also? I feel like mine has the EGR though, it has all of the emissions things installed still. Ideally I want to do all the work I can with the exception of refrigerant handling, as that’s mostly the point of this truck for me so I can learn these things. I think investing in the tools will make sense long term, considering I spent $300 on the spring compressor alone when doing front end, all of that seems much more reasonable. The awesome guy who handles all my hvac at my rental learned his stuff in the army as well and is super knowledgeable, so I’m sure you are too! Thank you for all of the advice.

It depends on whether yours is federal emissions or Cali emissions. A 1980 8600GVW truck means it was over the light truck weight limit for emissions, therefore it did not require a cat or EGR. It may or may not have a charcoal canister. It could also be a canada truck, in which case it would also have a Cat like @Catbox truck.