Hello- I have completed the reman long block engine swap on my 2001 Dodge Ram 1500 5.9L. In the process I destroyed the QD fitting on the high pressure output line from the condenser. I had to replaced the condenser , the high pressure line, the dryer/desiccator and all of the O-rings and gaskets. I added about 2 oz. of PAG oil to the compressor before re-assembly to account for the new condenser, new dryer and other losses. Ran and passed a 12 hour pressure test at 120 psi. Then got a loaner vacuum pump from O'Reilly and pumped the system down for about 4 hours to approximately -28 inHg. Then passed another 12 hour leak test at vacuum. I recharged the system with 134a ( without the stop leak additive).

Ran the system at MAX AC with the truck doors open, here are the results:
Ambient Temp: 70F (21C)
Low side pressure: 32 psi
High side pressure: 150 psi
AC dash vent output temp: 43F (6C)

These results seem reasonable to me, but the 134a recommended performance data suggests I may be a bit under charged. I on the other hand think I might be somewhat overcharged. There is a lot of condensation on the low pressure side at the dryer and the return line all the way to the compressor. I do know you want only gas coming back to the compressor and not liquid. Of course its not too hot here in Colorado at this time of the year, in terms of testing performance, but I will be heading to Florida next week and a fully operational A/C system is a must have.

Any thoughts or recommendations?

 

According to the charts, you might be just a bit under-charged. Not sure adding more refrigerant is going to improve performance any though......

 

I am at 6000 foot altitude, I suspect the generic 134a tables are baselined at sea level . Need to think/ponder about that potential affect.

on a related subject- I don't appear to be getting any fan output on the first 2 speed selections, but the 3rd and 4th seem normal- any thoughts on that?

I guess my back up plan will be to bring my gauge set along and some extra 134a and re-evaluate when ai get to seal level in Florida

 

Internal pressures are going to be unaffected by atmospheric pressure. It's a closed system.

As for the fan speeds, likely the blower resistor is burnt on those two speeds.

 

Are the fan speed resistors located at the fan speed control panel or somewhere else?

 

Should be somewhere on the heater box, accessible without disassembling half the truck.... Not sure exactly where..... Service manual will show it, get yours here.

 

Did you happen to look at the service manual to know how much to put in? When I did mine it called for a amount(don't remember) but you needed three of the small cans of Refrigerant. I didn't to break the seal on the third can because it was working fine with two. It called for just a little bit more than two cans.

 

43* is pretty good, I'd leave well-enough alone

The resistors are stupid easy from passenger foot well. I actually just keep one on the shelf because I service six 2nd Gens

 

yep…. Put a new resistor module in today and that did the trick. I’m also replaced the fan and motor because I read elsewhere that the resistors probably fried because the fan bearings start wearing out and increase the current load on the resistors, especially at low speed.

oh man that third bolt on the back of the fan housing was a challenge to get to.

its all running fine now- thanks for the advice friends