A/C questions

[Justin Fleming]

On my 86 k5 I was fortunate enough to have some cans of r12 floating around and I recharged my systeem. But my system seems to have a leak somewhere. So as I was diging into things I notices that when I shut the truck off after having the a/c on I heard a hissing noise up by the passenger side fire wall in the engine compartment. So I started the truck back up and turned the air on and I felt some air blowing out of the box where the a/c lines go in. I dont know the name of the component in there, but it looks like a heater core. I think it is either the evaporator or the condensor or the dryer. hopefully this is where one of you guys could help me out. so I continued to tear apart the compartment and when I started the truck up with the air on again I noticed that air was blowing off of this component. Is that normal? I think this piece is bad as I assume it should hold pressure and not blow air off of it. It is really hard to detrimine where the air is blowing off of it.

If you know a/c please give me a hand....


thanks

 

[Justin Fleming]

So I have detrimend that the device is the evaporator.......

Now wondering if it should hold pressure or should I beable to feel air blowing off of it???

thanks

 

[danny7139]

Sounds like a bad o ring, they sell a kit on lmc truck for about $7 for all the orings on the a/c system but you would have to fill it back up with r-12 as you would lose all of it when you are evac the system. Evac it then install the orings and a orifice while your at it (which is also at lmc and will make ur air cooler) run a vac test on it for about 15 mins and check for leaks. If it holds up then fill her back up with r-12 and there you go.

Also I've never tried it, but I hear if you use a ford bronco blue orifice your air will be cooler and run better.

 

[Justin Fleming]

Sounds like a bad o ring, they sell a kit on lmc truck for about $7 for all the orings on the a/c system but you would have to fill it back up with r-12 as you would lose all of it when you are evac the system. Evac it then install the orings and a orifice while your at it (which is also at lmc and will make ur air cooler) run a vac test on it for about 15 mins and check for leaks. If it holds up then fill her back up with r-12 and there you go.

Also I've never tried it, but I hear if you use a ford bronco blue orifice your air will be cooler and run better.

There was not a leak at any of the o-rings.....Like I mentioned above it appears that the evaperator was putting off air as if it was leaking once pressurized....I am not sure what the orifice thing is that your talking about....

 

[gone huntin]

You feel air because the blower motor is right there blowing across the evaporator. You can wrap where the lines go into the evaporator with some "a/c" tape and it will slightly improve the a/c performance. The hissing noise is normal when you shut the truck off with the a/c on. Get a squirt bottle with some soapy water in it and spray all of the line connections to look for leaks as long as there is still pressure on the system. Was it out of freon, or just low? If it was out, did you run a 20 min.vacuum on the system before you charged it?

 

[4xcrazy]

the hiss you hear after shutting the system off, is the system pressure stablizing, equaling out, the compressor has compressed the gas and was pushing it through the O-tube, the pressure is basically "bleeding" off, not really sure how else to explain this.

 

[Justin Fleming]

hum

Well I sprayed every thing down and did not see any leaks. I did however take the evaperator and pull it away from the blower motor while running and I could still feel the air.....The system was filled and now the compressor turns on and off cause the system is low again. I pulled the evaporater out of the truck now and I still have not found any holes in it. Is there a way to check this? I probably took this all apart for no good reason.....Dam it....

 

[opfor2]

Sounds like a bad o ring, they sell a kit on lmc truck for about $7 for all the orings on the a/c system but you would have to fill it back up with r-12 as you would lose all of it when you are evac the system. Evac it then install the orings and a orifice while your at it (which is also at lmc and will make ur air cooler) run a vac test on it for about 15 mins and check for leaks. If it holds up then fill her back up with r-12 and there you go.

Also I've never tried it, but I hear if you use a ford bronco blue orifice your air will be cooler and run better.

I wouldn't get anything for the AC from LMC, there over priced and probably sell crap at that. Take a look at these two AC companys they also have a/c forums:

http://www.ackits.com/

http://www.acsource.com

 

[Justin Fleming]

the hiss you hear after shutting the system off, is the system pressure stablizing, equaling out, the compressor has compressed the gas and was pushing it through the O-tube, the pressure is basically "bleeding" off, not really sure how else to explain this.

where is it bleeding off at?

 

[Justin Fleming]

I did pull the orifice out just to take a look at it and it did have either dirt or metal shavings in the screen. I know people say to replace it with a ford blue orifice.....Is this something that I should do?


Now that the system is completly empty I should go ahead an replace all the orings everywhere. Once I do this can I turn the a/c back on to pressurize the system again to check for leaks again or can this cause damage? I know that I would have to jump the swith to get the clutch to engage..... eventually I would take it somewhere to have someone suck it down add new oil and put 134 back in it......

thanks

 

[cbbr]

I did pull the orifice out just to take a look at it and it did have either dirt or metal shavings in the screen.

Get the system flushed, replace the orifice tube and the accumulator (I think is what its called) and make sure to vaccum it down for 1/2 hour befoe putting more R-12 in it. If the filter has crap in it, you need to get the system clean first.

 

[PsychoticDeadGuy]

hey, if you ever come out to CA, i will give you my entire AC system that works great for a small price.

 

[Justin Fleming]

Get the system flushed, replace the orifice tube and the accumulator (I think is what its called) and make sure to vaccum it down for 1/2 hour befoe putting more R-12 in it. If the filter has crap in it, you need to get the system clean first.

what is the accumulator that you are talking about? why should that be replaced?

 

[gone huntin]

The accumulator is the cylinder looking thing in front of your evaporator, it is the filter of the system. It cannot be serviced, it must be replaced. I STRONGLY recommend having the system flushed at this time if there was metal on your orifice tube and replace the accumulator. You cannot check for leaks without the system being fully charged with freon. If you do not have access to a vacum pump then I would leave this to the professionals (like me ). I would also leave this unit R12 as long as possible, converted units just don't cool as well.

 

[opfor2]

Ya, once U open the system up U should replace the accumilator and O tube. I would use the Ford Blue O tube in place of the OEM GM O tube. Make sure that you pull vacuum of at least 29 Hg's for at least 30 to 45 min, remove vac for about 30 min and check the guages for loss of vacuum. Having a guage set is a must!! Once U checked the guage set and it didn't lose any vacuum, pull vac for another 30 min then charge with the proper r12.

dan

 

[Robert D]

Hi guys, I am purchasing a 91 Blazer (fullsize) tomorrow for 1500. The only problem with the truck is a non-working A/C. It was used primarily as a hunting truck and has 144k original miles. Should I suspect the problem with the A/C is with the hoses? I'll be able to dig into it once I own it, but I'm wondering what else usually goes out on these things. My last vehicle was an 88 Porsche 944S and the compressor on that car was usually the problem...thanks for your thoughts.

 

[rjfguitar]

Hi guys, I am purchasing a 91 Blazer (fullsize) tomorrow for 1500. The only problem with the truck is a non-working A/C. It was used primarily as a hunting truck and has 144k original miles. Should I suspect the problem with the A/C is with the hoses? I'll be able to dig into it once I own it, but I'm wondering what else usually goes out on these things. My last vehicle was an 88 Porsche 944S and the compressor on that car was usually the problem...thanks for your thoughts.

It probably has a blown compressor, If this is the case then the A/C system will basically need to be overhauled.

Original poster,

Your best bet with A/C systems is to take it to an A/C shop and have them do it. If you don't fully understand the system and, most importantly, have the right equipment then you are probably just looking for trouble. You have to get the exact amount of freon into the system, Too much and it will not be as cold as it's supposed to be and will make the high side pressures too high making the pump want to lock up. Too little freon and it will be not as cold as it should be and could short live the pump if it's just barely enough freon to keep the low pressure switch from kicking.

A/C's are generally tricky, they are not something to mess with without the proper knowledge and equipment. I learned this the hard way by ruining new A/C parts. I'm not saying you can't do it, it can be done with the knowledge, guages, freon, and a thermometer in the vents. Thats the way I do with with most of our systems but thats after learning from someone and screwing up plenty on my own in the past. Regardless, you can't beat the new equipment that sucks old reon out, sucks down, and recharges the EXACT amount the system holds, recommended by OEM.

You will probably be money and frustration ahead to have a good shop do it for you. Yes, the bill will be steep, but it comes with a full warranty (many times aftermarket A/C parts have problems) and the system will be properly setup to provide full cooling performance.

 

[89GMCSuburban]

Man, you are at the point where a R134 conversion is THE best option. Replace ALL O-rings with 134 rings. Flush the system to get the mineral oil out. Replace the Accumulator and Orifice Tube. Use Ester oil to refill. When you refill the system, use just a tad less 134a than the system needed for R12. For example, if it needed 3 lbs. with R12, fill it with 2.8 lbs. of 134A.

Some people complain of cooling efficiency loss with the switch...the problem is 134a operates at higher pressures and does not cool as well in the tube and fin style condensors on our trucks. www.ackits.com sells condensors better suited for 134A systems. You might have to get some hoses crimped to make the thing work, but that's not too hard to get. We do it here at the Freightliner dealer all the time.

As to vacuuming for 45 mins at 30 hg., that's overkill, and you can actually suck the seals into the system doing it that long. Standard by ASE is a vacuum at 29 to 30 hg. for 15 minutes. Leave the thing hooked up, if it starts loosing the vacuum when you haven't touched anything, you have a leak.

The accumulator's function is basically like a receiver-dryer but it's on the front side of the evaporator. It is filled with dessicant to dry out the freon in the sytem of moisture before it goes through the evaporator. If the system has a leak and moisture has been getting into the system, the accumulator gets filled with moisture and can actually start blowing it and pieces of dessicant into the system clogging it or blowing the compressor. Good idea to replace this $30 part.

We test for links at the shop by regulating some pressurized Nitrogen at about 300-350 psi. into the system and spraying down the entire system with soapy water. See bubbles? Voila!

The system won't create pressure without any freon in the system, so you can't just turn it on empty to check for leaks.

Question about the orifice tube...did it have any black stuff on it? Actually, a pretty good amount of black stuff? If so, I'm very very sorry, but you will have the experience of fixing a system with black death.

 

[Justin Fleming]

Man, you are at the point where a R134 conversion is THE best option. Replace ALL O-rings with 134 rings. Flush the system to get the mineral oil out. Replace the Accumulator and Orifice Tube. Use Ester oil to refill. When you refill the system, use just a tad less 134a than the system needed for R12. For example, if it needed 3 lbs. with R12, fill it with 2.8 lbs. of 134A.

Some people complain of cooling efficiency loss with the switch...the problem is 134a operates at higher pressures and does not cool as well in the tube and fin style condensors on our trucks. www.ackits.com sells condensors better suited for 134A systems. You might have to get some hoses crimped to make the thing work, but that's not too hard to get. We do it here at the Freightliner dealer all the time.

As to vacuuming for 45 mins at 30 hg., that's overkill, and you can actually suck the seals into the system doing it that long. Standard by ASE is a vacuum at 29 to 30 hg. for 15 minutes. Leave the thing hooked up, if it starts loosing the vacuum when you haven't touched anything, you have a leak.

The accumulator's function is basically like a receiver-dryer but it's on the front side of the evaporator. It is filled with dessicant to dry out the freon in the sytem of moisture before it goes through the evaporator. If the system has a leak and moisture has been getting into the system, the accumulator gets filled with moisture and can actually start blowing it and pieces of dessicant into the system clogging it or blowing the compressor. Good idea to replace this $30 part.

We test for links at the shop by regulating some pressurized Nitrogen at about 300-350 psi. into the system and spraying down the entire system with soapy water. See bubbles? Voila!

The system won't create pressure without any freon in the system, so you can't just turn it on empty to check for leaks.

Question about the orifice tube...did it have any black stuff on it? Actually, a pretty good amount of black stuff? If so, I'm very very sorry, but you will have the experience of fixing a system with black death.

How do I flush/ clean out the system? And what is a system with black death?

 

[cbbr]

How do I flush/ clean out the system? And what is a system with black death?

You can buy a kit to flush it, or just take it to a shop. Black death is what was in your orifice filter. The metal shavings come from wear on the compressor from being run while out of freon. Your best (and cheapest, ask how I know) bet is to take it to a pro.

My bet is that if you will need a new compressor, accumulator, orifice tube and a good flush/draw down before you want to waste anymore freon.