Correct port and pounds for AC recharge

[johneich]

My 83 has been converted to 134a and blew cold last year, I ran it a few times over winter and in spring it was cold, now its warm. Put my gauge on the port marked "L", its on the drier, the other port marked "H" is on the compressor. Compressor turns on and off with the dash switch.

My problem=its showing 100 pounds at the L port on the drier, I think I should be about 30-35 pounds fully charged on the low side.

I searched tech articles and threads, I can't find what to do now. When it was converted to 134a could the ports have been reversed? I think they are different sizes but I dunno and don't want to make a mistake. I am thinking I have to be reading the high side??

John

 

[RLDSL]

Many times the universal R134a low side port adapters simply don't work properly with the ford pickup accumulator fittings for some strange reason and can cause you to get some really wierd readings and not be able to suck refrigerant in ( on my truck I just made a custom low side hose with a new r134a low side port in it ) but if you are getting strange readings and the compressor is running try a new adapter fitting or using a hose for your manifold gauge set that will allow you to attach to a r12 port to eliminate the attachment problem to make sure that you are getting an accurate reading.. Also try getting a box fan and setting it up in front of the rad and having it blowing across while taking the reading. Your fan clutch may be getting very weak

 

[johneich]

Today, new issue, now the compressor does not kick on and I am reading 75 pounds on the high and low side, I think I now need to jump the compressor but I don't know how, could somebody tell me please.

 

[icanfixall]

Try this. On the dryer bottle remove the wire connecter. Place a jumper wire in the connecter and see if the compresser runs. If it does your pressure switch in the dryer is bad. With 75 lbs on both sides of the system it sounds like its fully charged to me. The switch can be removed from the dryer without dumping the freon charge because there is a schrader valve behind the switch. Do wear some eye protection when you remove it. You never know what some ac tech may have done years ago and removed the schrader valve. I found this out the hard way on the wifeys Honda Civic when I was removing the switch. Honda does not use the schrader valve under the pressure switch. Big mess right there it was. I was wearing a full face shield and way able to get away from the deadly cloud. Neighbors probably got a laugh seeing an old man trying to run like a teenager...

 

[gingrass179]

if you have 75lbs on both sides it sounds like your exp tube is worn thru??? that is the only way to have equal pressures on both sides...and 35 is max you shouldnt put any more than that...if your are 35 on the around 250-300 on the high you are where you are supposed to be but if it is still blowing warm air you need to make sure you run a vacuum for a solid 30 min after that if still not cold enough your condenser is getting clogged

 

[Deib]

75 pounds on both high and low gauges is just fine as long as the compressor is not running.

Get the compressor running.
Either jumper the cycling switch on the accumulator or run a hot wire to the clutch on the AC compressor.

Sounds like the pressures are fine. You need to find the part the failed. Compressor clutch, cycling or low pressure switch, Fan switch in the cab, or broken wire somewhere in that loop.

 

[johneich]

Ok, I jumped the switch on the drier, compressor now turns and I have cold air, I let in run for 30 minutes, pressures are now 60 low and 140 high, any thoughts on these pressures?

 

[icanfixall]

Sounds ok to me. Now replace the switch. Most any wrecked Ford or Merc will have the exact same pressure switch because they are all the same systems. Or just pay the extra bucks and buy new.. Glad you found the problem and its an easy fix.

 

[gingrass179]

60 140 is not ok your low is too high and your high is too low...35low 250high is what you want...i work on a/c systems all the time here in phoenix and you see absolutely no gain from more than 35 on the low besides over pressuring your pump and run the truck to 1800rpm and see what your readings are...thats where you should run it charging and checking pressures

 

[OLDBULL8]

60 140 is not ok your low is too high and your high is too low...35low 250high is what you want...i work on a/c systems all the time here in phoenix and you see absolutely no gain from more than 35 on the low besides over pressuring your pump and run the truck to 1800rpm and see what your readings are...thats where you should run it charging and checking pressures

That's the way to do it to see if you have the correct pressures. But you have no way to know if the system is fully charged. Running at 1800 RPM , you can add a little more 134A until frost begins to form on the line out of the firewall to the accumulator then stop adding, remove the charge hose, then release some gas slowly in spurts until the frost disappears back to the firewall. That's how I do it.

 

[Devon Harley]

Would my clutch on my ac be going out if I have to spin it a lil and then she's good to go! Working perfect

 

[Deib]

The proper charge is when the inlet and the outlet to the evaporator are the same temperature.

Inlet colder than outlet = low charge
Outlet colder than inlet = over charge
Same temp = just right.

This should be checked at off idle like recommended. 1,800 is okay rpm we usually check it at 1,200-1,500
That compensates for a worn compressor.

 

[icanfixall]

Guys.. Lots of information is being posted here. Lets remember this system was converted to 134 from R12. The r12 runs differant pressures than the 134 and I think the tube needs to be changed for it to operate properly. Some have found installing a variable orfice tube works better. I still feel the perssures are ok and the pressure switch is bad. What oldbull posted about the return line frosting up is true too. Whats hapening is the freon is still pulling heat out of the return line back to the compresser. Thats shows too much freon in the system. Dropping some out till the frost goes away will fix it for the home garage type guy that some of us are. A really nice evap and recharge system would be great to have but thats not possible for many of us plus.. The new replacement freon is due out very soon. That will mean new recharge and vac systems. New gauges.. Another big chage just like what 134 was...

 

[gingrass179]

i havent heard about any changes when arethey talking about doing this

 

[johneich]

Update, I was blowing cold, I guess having the gauges on and off and on for so many times & long I let out some 134a, Its now blowing cool, I have only 10 pounds on the drier (accumulater?)

Someone please verify the low side is on the passenger side on the drier.

It does not take the contents out of the can, I hold it upside down and tip it, the can does not empty much,

I am lost as to what to do (again on this truck, but you guys have always helped me, thanks!!!)

After I let it rest for a bit the pressures equalized at 100 high and low, this is where I stand.

PS the evaporator, drier, O tube and charge were new last year by a local mechanic I trust.