AC Question's

Vicious · 05-11-2010, 10:23 AM

now that my car is running and everything seems to be in order im down to the final pieces for fixing, the AC. when i did the engine swap i left all AC connections intact and just connected it up to the new motor. when i turn the ac switch on the blower works, the cooling fan comes on, the aux idle valve opens and idle increases about 500rpms, and looking through the small view-glass under the hood i can see the fluorescent dyed refrigerant moving. now the problem is i have absolutely no cold air coming through the vents, if i touch my hand on the condenser? (one in front of the radiator) the line is hot which should be normal but i cant feel a cold line inside the cabin.
from what ive read on refrigerants they dont go bad as long as there is no leak it should still work, so is there a valve somewhere not opening? or does it just need a recharge

AaronM · 05-11-2010, 12:48 PM

The flapper doors in the duct work are operated by vacuum actuators. If there are vacuum leaks in the small lines coming to those actuators, the system may not switch over to the A/C ductwork which could stop you from getting cold air in the cabin.

What I would do first though is check the high and low side pressures with a set of manifold gauges. That will verify that you're getting the correct pressures on both sides of the system and if you are, then you know the refrigerant lines are OK. If not, then you know that you need to look for a blockage or a stuck expansion valve, etc.

mattdavis11 · 05-11-2010, 04:03 PM

If the fat a/c line running from the evaporator to the compressor is cold, it's vacuum related, otherwise the expansion valve is not functioning as it should.

bell · bell's Garage

yep, the flapper is controlled by a vacuum line which goes into the cabin right near the center of the engine bay, on the passenger side of the blower......
if the refrigerant were low the compressor wouldn't kick on......

Vicious · 05-11-2010, 05:40 PM

Air come through the vents when ac is turned on. touching the 2 lines inside the cabin neither is cold. where is the expansion valve located?

AaronM · 06:10 PM

Quote:

Originally Posted by Vicious

Air come through the vents when ac is turned on. touching the 2 lines inside the cabin neither is cold. where is the expansion valve located?

Based on the parts diagram, it looks like the valve is located in the same inside enclosure that houses the evaporator.

Vicious · 05-11-2010, 06:20 PM

is there a way to force it open without removing it? or removing it without having to evacuate the system?

AaronM · 05-11-2010, 07:26 PM

Quote:

Originally Posted by Vicious

is there a way to force it open without removing it? or removing it without having to evacuate the system?

Not that I know of.

Vicious · 05-11-2010, 08:39 PM

after running the compressor for about 5 min's i felt all the line's, only one was hot the large one coming from compressor to the condenser. the small line coming out of the condenser was cold as were both lines inside the cabin. would that be normal of a expansion valve problem? perhaps the condenser needs a flush? im at a loss tryn to understand how the incoming line on the condenser is hot and the output isnt.

AaronM · 05-11-2010, 11:58 PM

Quote:

Originally Posted by Vicious

after running the compressor for about 5 min's i felt all the line's, only one was hot the large one coming from compressor to the condenser. the small line coming out of the condenser was cold as were both lines inside the cabin. would that be normal of a expansion valve problem? perhaps the condenser needs a flush? im at a loss tryn to understand how the incoming line on the condenser is hot and the output isnt.

Cold or cool? The line coming out of the condenser shouldn't be as hot as the line going in, the whole point of the condenser is to pull heat out of the refrigerant, so the output line should absolutely be cooler than the input line.

At this point you've gone from saying that the lines going into the passenger cabin to the evaporator were both warm to saying that they're both cold. I think it's time to have a qualified A/C technician look at the system rather than continuing to guess at it. At the very least, do as I suggested and hook up a set of manifold gauges so that you can see what the high and low side pressures are. That will tell you much more than you'll find out by feeling up the A/C hoses.

mattdavis11 · 05-12-2010, 03:58 AM

My guess is he doesn't have a set of gauges. There are pawn shops everywhere that have them and you should be able to get them very cheap as R12 gauges are pretty much obsolete, which is precisely the angle I would use when talking to the pawn broker.

I'd personally look for a set of Mastercool gauges and inspect the sealing o-rings at both ends of the red, yellow and blue hoses. If they are torn up, I'd use that as leverage when purchasing to knock down the price even more. You can replace the orings inside the fittings. Also make sure that both needles are not damaged and zeroed out. Some gauges you can zero out by removing the plastic covers and turning a screw with a jewelers screw driver.

John_AZ · 05-12-2010, 05:12 AM

Quote:

Originally Posted by mattdavis11

If the fat a/c line running from the evaporator to the compressor is cold, it's vacuum related, otherwise the expansion valve is not functioning as it should.

Quote:

Originally Posted by AaronM

Cold or cool? The line coming out of the condenser shouldn't be as hot as the line going in, the whole point of the condenser is to pull heat out of the refrigerant, so the output line should absolutely be cooler than the input line.

At this point you've gone from saying that the lines going into the passenger cabin to the evaporator were both warm to saying that they're both cold. I think it's time to have a qualified A/C technician look at the system rather than continuing to guess at it. At the very least, do as I suggested and hook up a set of manifold gauges so that you can see what the high and low side pressures are. That will tell you much more than you'll find out by feeling up the A/C hoses.

Quote:

Originally Posted by mattdavis11

My guess is he doesn't have a set of gauges. There are pawn shops everywhere that have them and you should be able to get them very cheap as R12 gauges are pretty much obsolete, which is precisely the angle I would use when talking to the pawn broker.

I'd personally look for a set of Mastercool gauges and inspect the sealing o-rings at both ends of the red, yellow and blue hoses. If they are torn up, I'd use that as leverage when purchasing to knock down the price even more. You can replace the orings inside the fittings. Also make sure that both needles are not damaged and zeroed out. Some gauges you can zero out by removing the plastic covers and turning a screw with a jewelers screw driver.

What mattdavis11 (real life auto AC technition) and AaronM (qualified ornery love child

) are trying to say is "Its all about temperature".

I found out my home AC technition teaches auto refrigeration at a local school and he put me on to the infrared thermometers. Prices start at about $10 to $40 at Harbor Freight.

After many years, Matt has calibrated his hands to the "feel" or the temperature of the lines. This is a link that explains for the rest of us:

It's ALL about HEAT and TEMPERATURE!

GL
John_AZ

Vicious · 05-12-2010, 10:29 AM

let me clarify, when i said cold in the last post i was not implying the full meaning of cold. i meant that the large line going in was hot yes, the small line coming out was ambient temperature otherwise there was no change noticeable, same for both the lines inside the cabin. i dont have any gauges right now, ill try and get some this weekend hopefully.

mattdavis11 · 05-12-2010, 04:11 PM

You got the travel backwards. The small line carries the compressed refrigerant (after it passes through the condenser and drier) to the evaporator, then the expansion valve turns it into really cold vapor, the line returning to the compressor (fat, or suction side) will be cold, some times even icing up on the metal in cases of low charge.

Something tells me your expansion valve is stuck. If that's the case, the freon must be evacuated, and I'd choose carefully who evacuates the system, they know it's worth $50 plus per lb and could milk you. Once that is done, I'd back flush the expansion valve before I replaced it, but then again it's hard for me to tell someone else to do what I'd do. The valve is less than $15, but can be difficult to change.

Let me know how I can help, we have people in Houston that will take parts to your door.

Vicious · 05-12-2010, 05:55 PM

You have a shop here in Houston Matt? Or know ppl here. What's avg cost to do a backflush? I wouldn't expect them to recharge since it's r12 and I plan on using freeZe 12 in it's place.

HondaDustR · 05-13-2010, 08:34 AM

Yeah, they are in this order:
Compressor discharge side, receiver drier, condensor (line from drier going in should be hot, line leaving should be warm), expansion valve (should be very cold immediately exiting going to the evaporator), evaporator (should be less cold leaving than entering), compressor suction side (should still be somewhat cold).

mattdavis11 · 09:13 PM

I don't know of any reputable shops in Houston, I've only visited a few times. Harlow Gears used to have a good driving range, though.

Back flushing is an art, you can paint a driveway with dye in a hurry. What you are doing is sending flush through the valve in the opposite direction of the flow of the refrigerant. The flow is mentioned above, duster elaborated correctly.

It's no different than flushing any other way I know, you chase the flush with compressed air, hold your thumb over high side line and release now and again. You'll see the trash if you catch it with a cloth or bottle. If it's stuck open (most likely) it'll run right through at first, then my guess is it'll start acting right, and pressure will build at the nozzle of your air supply, please don't look to check why. All you have to do is release at the other end catching what you want to observe. By observe, I mean what kind of trash was found in the system judging by the feel, color, odor, taste of the flushed particulates. I can't train you ear to hear fluid being flushed.

There's going to be a mess, cover your eyes, it burns.

I was a little bit out of line last night, and I didn't think about it until now. I service, provide technical support, and sell a/c parts. This site harbors what I have to share and it would be unfair of me to tell you who I associate with. I'd buy the part here, I was ball parking and being truthful at the same time.

Vicious.....Tell them you have R12 and want to swap for Freeze12, they'll appreciate that, if you have pure R12. They get your R12, they do all the work, you leave with $0 bill. That's the way I'd approach it. I have no opinion on freeze 12.

Vicious · 05-14-2010, 03:21 AM

thx i appreciate the help, never done any work with ac systems just the mechanical/electrical side. is there a decent guide for performing the backflush yourself? or would i be doin this in similar style to a radiator flush, disconnect the lines add cleaner of some sort hold one side apply pressure to other etc..

mattdavis11 · 05:09 PM

Exactly the same, just make sure you run it from the low side to the high. Fat to small, build pressure, release. As a flush, I'd recommend denatured alcohol, you can find it any home improvement store in the paint section.

If you don't flush the condenser, and you never would flush the drier, I bet you lose 2- 2.5 ounces of oil the system requires. Add that back.