Can we talk AC????

[jimraelee]

Well my new truck has a flaw... bad defrost. After inspecting the ac system, I found it was a bit low on freon... no big deal... dumped in 2 lbs of freon and pres is still on the low side, the high pres side ( should be 2.5 times ambient) is only pumping 50-75psi.. Sounds like the pump is trashed. Looking at new pump, dryer and orphas tube. What are my alternatives for Freon... R12 was on its way out when I was in the bizz.(some 10yr ago) and R134a is the new cool refrigerant. Is there a compatible gas to use in a R12 system??? I don't really want to change out all the rubber lines and swap over totally.

thx

 

[argve]

Most say that the way I do it will kill the system but I haven't seen a problem in the systems I have done in over 5 years.

I vacuum down the r12 system and recharge with r134a oil and r134a refrig - I didn't change anything other than those two items. I used what so many of the guys call death kits (convert kits) I picked mine up at Meijer dept store because they were the cheapest around.

 

[RLDSL]

You don't need need to change out all the rubber lines, they thought that at first, because the old style line would allow r134a to pass, but what was found is that old style r12 lines that had been in service with r12 had been saturated internally with mineral oil and will not allow r134a to pass through, so there is no need to replace all your rubber lines. At the points where you do open the system and need new orings, do not lubricate the new orings with the new synthetic ac oil( you will need it for the retro fit), it will dry out the orings and cause leaks, get a can of the old style mineral oil for lubing the orings( shop around, most places will try to tell you its rare and charge $30, you should be able to get a qt for $12 ) or get some Nylog for the orings.

Those cheapo retrofit kits work OK, Make sure to replace the accumulator and orifice tube(and if you want it to really get cold, get a variable orifice valve, costs about $35 and worth every penny if in a hot climate) You don't have to get the old oil out of the system, but if you can blow it out you will get more accurate readings. If there is any signs of black/grey residue in the system metal filings etc from internal compressor failure you will need to remove all the componants and flush thoroughly or you'll be doing it again soon.

 

[BigRigTech]

I did the same thing, works great so far.

 

[jimraelee]

Thanks guys... Yes I would always replace the orphas and accum when opening any ac system... to me its just a standard... didnt know about NOT changing the rubber lines... good to know... Ill give it a try soon, probably in the early spring when the temp rises above 50....

 

[Dirtleg]

I had to do mine immediately after purchasing my truck as the A/C was non-operational. Pretty much everything mentioned is good advice. Definitely put in all new o-rings if you've got the system open. I didn't know about the variable orofice tube prior to my repairing the system but would have gone that way if I had.

The only other piece of advice I can offer has to do with the low pressure switch. The 134a will run at a lower pressure on the low side of the system. I had hell charging my system because the compressor wouldn't run. It was short cycling. If , and only if you are having this problem try this.

On the low pressure switch, in between the electrical connections is a screw. It is the adjustment for the low pressure switch. It was set at 25 psi for R12(thats the pressure the compressor was turning off at) but I backed it out until the compressor was running at 19-20 psi. I was then able to fully charge the system. An A/C shop tech taught me that one. I believe the high pressure was around 175 but could be mistaken. It's been a while and my brains had some miles put on since then.

 

[SD70Ace]

Your pressures dont mean much at idle. Both hi and low sides have low pressure at idle. That means your comp might still be pumping good. But if you rev it up and discharge pressure goes thru the roof and suction bottoms out, your metering device might trashed out.

 

[RLDSL]

The adjustable pressostat on these things is great once it's charged up, but for charging a system up from empty, the easiest way is to unplug the thing and run a jumper wire across the terminals until it gets up near full charge. Saves a lot of time .
For pressure temperature go to this site and download the free program, the AC advisor, to help calculate high side pressure for ambient temp and some other handy ac calculations

Try not to read the news about the up and coming *new* R744 CO2 ac systems that are going to be the new mandatory environmentally *safe* setup that we're all going to have to put up with next ( er, I thought we were trying to cut Co2 production..oh heck, never mind , and that r134a is going to be illegal in kalifornia soon for individuals to purchase.....does any of this sound familiar.....

 

[MIDNIGHT RIDER]

if you want it to really get cold, get a variable orifice valve, costs about $35 and worth every penny if in a hot climate

Considering that I am about dumb as a rock about A/C, please explain just what this variable valve is and what it does.

What does it do to make things colder ??

Does it automatically "vary" itself; or, is this variability user selectable ??

Thanks.

 

[jimraelee]

Yup we use to just jumper out the low pres switch when charging... actually opened the valve on a fresh vacuumed system, then let tank pres fill system, jumper out low pres switch, and start the vehicle.

Never had a program to tell me what high side pres should be.. rule of thumb was 2.5 x outside temp... Oh and a guy I just met over the hill from me told me about a more efficient condenser NAPA sells... he says its worth the Buck and a quarter they charge.

 

[RLDSL]

Considering that I am about dumb as a rock about A/C, please explain just what this variable valve is and what it does.

What does it do to make things colder ??

Does it automatically "vary" itself; or, is this variability user selectable ??

Thanks.

Basically the orifice valve is a tiny little hole that seperates the high and low pressure sides of the system. for arguments sake, near liquid refrigerant enters the valve at high pressure and goes through the little hole and enters the low pressure side of the system, causing it to expand and enter a gasseous state making it nice and cold problem is that fixed hole isn't always the right size to keep the pressure where it would work the best. That's where the variable orifice valve comes in. When it''s really hot out, it varies the rate that the hole opens to maximize the evaporator temp ( or minimize it if you want to get picky) As pressure rises, the hole opes less to not allow liquid refrigerant through. In hot climates it can make a difference of about 12 deg f coming out the ducts. In cold climates, they don't make much difference since the presure on the high side doesnt climb ( what the heck are you guys in Saskatoon doing with AC anyway but here in the hot humid south, they make a huge difference. I mentioned it for the original poster since I didn't know if he was in costal Oregon or southeastern Oregon out in the desert
I put one of those and an electric pusher fan on every system I go into around here. First one I did on a volvo 740 wagon ( notoriously poor factory air on r12, pitiful on r134 ) the lady's husband started griping that he was freezing to death in the thing Been using them ever since.

They are available from Napa and Advance under various part numbers
In real hot climates get the ones for extreme climates 105 deg +
Combine that with adjust ing the pressostat down for the r134a and it will get nice and cold. Glue a layer of reflective insulation around the evaporator /blower housing on the underhood side and that helps a whole bunch too.

 

[typ4]

RLDSL, thanks for posting that link. I have a VOV but didnt know the technical aspects. Also there is an update condenser for our trucks that my buddy who has a shop that does lots of ac got for me, higher efficiency I think he said for retrofits. My ac works really well but I am going to turn down the switch and try it this summer.

 

[RLDSL]

RLDSL, thanks for posting that link. I have a VOV but didnt know the technical aspects. Also there is an update condenser for our trucks that my buddy who has a shop that does lots of ac got for me, higher efficiency I think he said for retrofits. My ac works really well but I am going to turn down the switch and try it this summer.

Someone had mentioned the other day that he thought a parallel flow condenser out of about a '97 would fit. I havn't had a chance to look into it, but it sure looks like I could rig one of these in without any trouble And would have regular o ring fitings. Chances are a '97 would have those stupid slip lock fittings and I'd have to adapt them over.
I want to go a bit nuts on my crew cab and either rig an extra evaporator/blower in the back seat for the kids or run some extra ducts back there under the floor for them to keep them cold back there. Air flow to the back seat stinks. Ducts are ice cold, but it takes too long to cool down the kids in the back.

 

[jimraelee]

I mentioned it for the original poster since I didn't know if he was in coastal Oregon or southeastern Oregon out in the desert
I put one of those and an electric pusher fan on every system I go into around here. .

1) whats the pusher fan you speak of??? Some dash mount fan....
2) I live west Oregon in the Willamette valley. I want the ac to help improve the Defrost in the truck... I fog up at times, and have to full blow the heater to keep it at bay. Working AC should really help keep the fogging up to a minimum. Thanks for the link on the variable orifice tube.
jim

 

[The Warden]

I havn't had a chance to look into it, but it sure looks like I could rig one of these in without any trouble And would have regular o ring fitings. Chances are a '97 would have those stupid slip lock fittings and I'd have to adapt them over.

I would love to hear your progress on that!!! I want to do the same with my truck, when $$ allows. I want to install an intercooler at the same time, and re-locate the condenser outboard of the IC (similar to how most newer trucks are set up).

I converted my truck to 134a shortly after I did the turbo swap...there was a minor leak somewhere, and my blower fan isn't working properly, but it seemed pretty happy otherwise. Unfortunately, the threads in one of the manifold bolt holes in the compressor stripped, so I blew an O-ring out last year...Heli-Coils didn't work, so I need a new compressor (and, by now, probably need to go through the whole system again )