A/C operation problem: any ideas or?

[Coley]

...I'm not exactly sure where this thread is best served but regardless here is my issue.
The a/c in my truck used to work and I believe it may have been converted at some point to a newer type refrigerant
Regardless, right now when I turn it on, it doesn't blow particularly cold so I checked a few things under the hood.
Everything appears to be operating properly (mechanically, etc) including the compressor, clutch, vacuum control points etc.

However....the piping near the firewall and the main a/c firewall box has an interesting condition.
the lower, small 'u-pipe' is very frosty and quite cold to the touch. However once it gets up to the 'expansion valve'?? it goes into a larger, upper U-pipe that then curls into the main firewall unit. This larger, upper U-pipe isn't cold at all.
A lot of the crew here are really up on the a/c systems so I thought I would ask if there are any ideas as to what might be going on with this system?
...here is a quick pic of a system typical of what I have under my hood. I've tried to mark/identify these 2 different pipes in the drawing so hopefully they show up ok.
...any ideas, etc from the a/c experts are more than welcome.
All good
Coley

[leddzepp]

Low on refrigerant or a stuck poa valve. I just restored the factory AC in my 68 and had this same condition when I put the first can of freon in. After researching the condition it seemed it was one of those two things. I added two more cans and on the third everything equalized and the frost went away. The evaporator got nice and cold and the system works flawlessly so far...just monitoring for any leaks. You need a set of gauges to check your pressures to start with and go from there.

[weq92f]

^^^^^^!

Gauges can be had for pretty cheap these days. With a little reading, and the gauges, you can figure out whats wrong with it, maybe even fix it!

-klb

[stsalvage]

Love seeing old factory AC coming back to life I hate the aftermarket type I like my glove box

[Wrenchbender Ret]

I used to run in to that a lot years ago when I did a lot of A/C service. I would tap on the valve with a hammer & it usually freed it up. A lot of guys are changing the POA system over to a cycling system. They have kits for this. I don't like the idea as it doesn't look original. The old system worked good for many years. It does hurt gas mileage more though.

[Coley]

Originally Posted by Wrenchbender Ret

I used to run in to that a lot years ago when I did a lot of A/C service. I would tap on the valve with a hammer & it usually freed it up. A lot of guys are changing the POA system over to a cycling system. They have kits for this. I don't like the idea as it doesn't look original. The old system worked good for many years. It does hurt gas mileage more though.

...now that sounds like an interesting 'first approach'....not too labor intensive first time out...lol.
I will give this a try.
Are the effects pretty apparent if it 'free's up'? ...... 5 minutes to show up at the vents or?

C.

[weq92f]

I think it would be near instantaneous for the 'cold pipe effect' to show up on the upper loop, just past the valve, if the compressor is running when it frees up.

-klb

[Already Gone]

subscribed

[Andy4639]

Per your picture the system is changed to 134-a. The blue cap is a given. Low side for the froen.

High side should have a red cap on it. No threads on either connection.



I also like the factory look but I took mine a bit further and added a later model system to it.

[weq92f]

OP mentioned the pic is just an example me thinks.

-klb

[Andy4639]

Originally Posted by weq92f

OP mentioned the pic is just an example me thinks.

-klb

As stated typical of his so it has been upgraded which he says his has are thinks it has.
Which you could be right but I give him credit for knowing what is in his truck!

At least what it looks like anyway!

here is a quick pic of a system typical of what I have under my hood.

[weq92f]

An accurate example. I stand corrected.

[Coley]

Ok updated....see included pic.
I took and 'tapped' on the (POA?) valve to see if there was any effect....nothing yet.
So its cold and frosty right up until the center fitting on that first section of the valve (see pics)....after the center of that fitting....normal temperature.
The little aluminum (1/4"?) bent pipe that curls up and heads inside the main firewall box is cold as well.

any ideas as I keep troubleshooting this?

All good
Coley

[ApacheIvan]

I have an AC question as well. Is the muffler on top of the compressor supposed to get so hot you can not touch it?

[Andy4639]

Originally Posted by Coley

Ok updated....see included pic.
I took and 'tapped' on the (POA?) valve to see if there was any effect....nothing yet.
So its cold and frosty right up until the center fitting on that first section of the valve (see pics)....after the center of that fitting....normal temperature.
The little aluminum (1/4"?) bent pipe that curls up and heads inside the main firewall box is cold as well.

any ideas as I keep troubleshooting this?

All good
Coley

My suggestion is take it and have it serviced are if you want buy a orfice tube and do as I did and do away with it. You put the orfice in the line going up front. Take the connection loose slide it inside the tube re connect it. Buy accumilator and do away with the POA valve. Thats it.

[Andy4639]

Originally Posted by ApacheIvan

I have an AC question as well. Is the muffler on top of the compressor supposed to get so hot you can not touch it?

Is the ac working good? Is it cooling like it should.

It is a muffler you know!

[leddzepp]

A set of gauges needs to be hooked up to the system while it is running. Everything else is a turkey shoot until then.

[100%Chevy]

Working right,the muffler will be too hot to touch!
Also,there's a cappillary tube connected to the suction line coming from the evaporator to the pov.Remove the insulating tape,clean the tube and the suction line with fine emory cloth,then re-install it.this tube determines the pov's operation according to the temp sensed.If it's dirty or corroded,it's a bad connection and won't work.
Mike.

[davischevy]

A competent AC service man can evacuate the system and put the correct amount of refrigerant in it and it will work great.

You will save money in the long run having a professional charge it.

I had my Super's AC serviced over 8 years a go and when I drove it today I couldn't believe how cold it is.

I'm have an appointment for my Longhorn to get a new compressor and service before I take off to Goodguys Des Moines. I have to do it. If Mama ain't happy, nobody ain't happy.

[Coley]

Some great info here guys, many thanks.
The one thing about this a/c system is....I'm not going to sweat it (lol, pardon the pun).

I will take probably take it in for servicing and a recharge at some point.

The thing about having a/c in a lot of parts of Canada is that it is redundant most of the time because it just doesn't get hot enough to use it much.
We are having a real crappy weather season up here so far....I'm lucky if I don't have the heater on today...lol.
We are lucky if there are a 1/2 dozen days a year when you can have it on....however it is a nice novelty to have on the truck for show & discussion purposes....and, lets face it...its nice if it does work.

That said....R12 would have been the original refrigerant...correct?
Then replaced by R134?....what is the difference?...is it just internal or how would you know if your system has been converted?


All Good
Coley

[davischevy]

If converted to 134, the charge ports will have adapters screwed on top of them. They usually have a red and a blue plastic cap.

In your part of the world, a properly working original system will cool just fine with 134.a.