A/C specs - Diesel Forum

zekex2 · 07-19-2005, 05:26 PM

What should be the internal pressure on the pressure side of the A/C compressor be?

Anyone know this?

thanx [img]/ubbthreads/images/graemlins/shrug.gif[/img]

94_turbo · 07-19-2005, 09:18 PM

rephrase the question--dont quite understand---

Rick_Hipp · 07-19-2005, 10:28 PM

28-30 low side / 250-275 high side (R12)

30-35 low / 200-250 high (134a)

engine @ 12-15c rpm / 85 ambient temp

asavage · 07-19-2005, 10:52 PM

It depends on the prevailing conditions, but I like to see max 250 on the high side with R12. But we don't have really hot weather up here. Most rigs I see tend to run in the 150-200 range but that's with ambient under 80°. If I can get a 40° split (delta of outside air vs center dash outlets w/blower on high), I'm satisfied.

zekex2 · 07-20-2005, 05:01 PM

thanx guys. It's at 275 high side so I will have to liberate a bit of the R134.

zekex2 · 07-20-2005, 05:31 PM

So mu ambiant air is about 100 the low side is running at about 50 and the high side is at about 240 (after a little 134a liberation).

? What is up with the high low pressure? any ideas?

thanx

Rick_Hipp · 07-20-2005, 06:04 PM

Does it seem to cool better driving down the road and heats up at stop sign or intersection (sign of weak fan clutch). If not, I would say to replace the accumulator/dryer and do a 3hr vaccum (especially in your temps, it will be good). Possible air/moisture in the system causing the high low side. Add back the 134a slowly after the compressor stops cutting off. If possible, get a digital thermometer and measure the air temp coming out of the vent on driver's side (fartherest away from the evaporator).

zekex2 · 07-20-2005, 08:03 PM

I just got back in from playing with it.

I took the blower off because it has been making noise. stuvck my hand inside the housing and felt in the evaperator housing. It was packed with leaves. I pulled out what i could. without having to spend a whole day on taking the housing apart. split the evaporator housing as much as i could from the top side by taking put the screws, and housed it out a bit. cleared some of the evaporator fins off and just got it back together. I have much better air flow than before (of course) and am going to give it a drive out to a really warm place this evening. I will have better info tomarrow morning when I get back into town.

the air coming into the cab is cool but not really cold. I will see if it is better at highway speed than at idle. the truck is painted dark blue and is a crew cab with a sleeper cab attetched, so A/C had always been problematic. I just took of the sleeper a few weeks ago and now am trying to get this thing to be cool enough that I am not having to drink gatorade non dtop when I am driving it around here (soCal low desert type enviorment).

Thanks for your help, I will post new info tomarrow.

Rick_Hipp · 07-20-2005, 08:24 PM

I got a couple of evaporators off fo Ebay that have worked well. If you ever get a chance to remove the cowl at the windshield, put some screening under the slots to keep the leaves out. They can build up fast. That's one reason I replaced the evaps. Only has 6 nuts or screws holding the whole housing on the firewall. If you do a head gasket replacement, it's the ideal time to pull it off and clean 'er out.