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AC Specs Needed

AZ79K5Project

AZ79K5Project

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Anyone with a 79 - K5 with factory air? I need to know what the factory sticker says for the amount of R12 and amount of oil the system needs.

I need to get some work done on my AC system. I converted it to R134A a couple years ago and forgot how much freon it takes to charge it.

The factory service manual says 3 lbs 12 ounces which seems too high.
 
If you converted to 134a, then you want to charge about 80% of the original r12 charge.Which works out to about 3lbs.
 
That's what I initially did, using the factory manual as the source. The high side pressure was too high with three pounds.

I would like to verify the factory sticker on an R12 system if anyone has one just to make sure there isn't a misprint in the manual or another variation out there.
 
AZ79K5Project said:
That's what I initially did, using the factory manual as the source. The high side pressure was too high with three pounds.

I would like to verify the factory sticker on an R12 system if anyone has one just to make sure there isn't a misprint in the manual or another variation out there.
Click to expand...

How high?
 
Over 400 and tripping the high side switch at anything above idle. I'm not sure what's going on with this system, but obviously, something is not working correctly.
 
AZ79K5Project said:
Over 400 and tripping the high side switch at anything above idle. I'm not sure what's going on with this system, but obviously, something is not working correctly.
Click to expand...

Hmmm....

Generally an overcharge won't get you pressures like that on the high side. 'Specially such a slight over charge. 3lb's, even if a slight overcharge, is not enough to cause 400psi high side, regardless the refrigerant. Whats the condition of the condenser? Is it clean? Try pointing a fan at it while trouble shooting and see what the pressures do. You could also point a hose or splash some water on it. If the high side goes down, then there's some sort of problem with the condenser not cooling well enough.
 
I tried the water on the condenser yesterday. The pressure at idle dropped from 300 to 250 and stayed there. This wasn't consistent though.

The pressure went back up to around 300 after the engine was turned off for a few minutes and turned back on. I again used the hose, but the pressure really didn't change that time.

This all started when I discovered a leak at one of the connections after taking it for smog testing yesterday. First time driving it since May or June. I replaced the o-ring, evacuated it out, recharged to 3#. I was dropping the truck back off at storage it when I noticed the compressor cycling. The otherwise silent compressor is now making noise as a result.

I'm at a loss.
 
How long are you pulling a vacuum for? You need at LEAST 30 minutes. The longer the better. Don't let anyone tell you otherwise.
 
I didn't time it. I know it wasn't 30 minutes. I drew it down to 28 inches Hg. Would not pulling the vacuum long enough cause what I am seeing even though it held 28?
 
AZ79K5Project said:
I didn't time it. I know it wasn't 30 minutes. I drew it down to 28 inches Hg. Would not pulling the vacuum long enough cause what I am seeing even though it held 28?
Click to expand...
The only way not pulling a vacuum long enough would cause that is if you had a lot of moisture in the system and it was freezing and blocking the orifice.
Not likely.

Odds are its a blocked filter/dryer, and or a blocked orifice tube.

Some of the early filter/dryers were not compatible with 134A and its oil and would come apart.
If you changed it when you converted, you probably got the correct kind. But, they can still clog, or fail and dump crud into the orifice tube.

OK, before I make too big an ass out of myself, somebody confirm that that model uses an orifice tube.
I think it does, but its 1 in the morning, and I have been up for about 20 hours.

In fact, I'm going to bed.
Change the filter/dryer and pull the tube if its got one. Something is plugged.

J.
 
Fordum said:
... somebody confirm that that model uses an orifice tube.
I think it does, but its 1 in the morning, and I have been up for about 20 hours.

In fact, I'm going to bed.
Change the filter/dryer and pull the tube if its got one. Something is plugged.

J.
Click to expand...

The blue Ford tube is in this system. The R12 and R134A both call for orifice tubes. I am wondering if I wasn't getting enough air flow across the condenser with the electric fans even though the engine temp was fine. I have electric fans. It was 117 when I was working on it (143 or so at the condenser).

The condenser may not be close enough to the radiator allowing too much air to flow around the condenser rather than through it.

It seems like I didn't evac long enough.
 
Fordum said:
The only way not pulling a vacuum long enough would cause that is if you had a lot of moisture in the system and it was freezing and blocking the orifice.
Not likely.
Click to expand...

What he said. It's tough to trouble shoot A/C stuff without actually being there to see whats goin on. I was just checking the blocks, makin sure the simple stuff had been taken care of first.

As far as vacuuming, half hour at 29" (not 28) at least. Better safe than sorry.

Ford is right about the orifice tube too.

I'm still betting on there being an air flow problem around the condenser. Do you have a fan you can point at it? Even one of those big oscillating desktop fans would work, if you could get it close enough. What are your vent temps?
 
Best vent temp was around 76 (way too high). Outside temp 117, temp at condenser 143.
 
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