AC operation and system pressure questions

[GeoffM]

I was charging my ac yesterday by forcing the compressor on.
I used a gauge set, and saw various numbers. Sometimes, the
high side went as high as 200 psi. Then a valve (or something)
opened, the pressure dropped, and the fans kicked on. I saw the
high side pressure drop down to various low marks, nothing less
than 100 iirc. When this happened, I had cold coming out of my ac.

I ran out of refrigerant and stopping charging. I reconnected the
compressor, but it still doesn’t turn on by itself. The high side
(obviously) stopped building. I saw the pressure drop and fans
kick on twice, all the while still having somewhat cold air. After
the pressure stabilized around 100, no more cold air.

Before charging and after charging, the low side read around
75 psi, compressor off.

I still hold the belief that the system still needs more charge,
but I don’t know why the compressor isn’t kicking on. Any
ideas/normal system pressures?

[oyajicool]

Haynes manual for A/C and heating calls for 25-35 for low side and 200 for high side.

It sounds to me your system is undercharged, still. But, I could be wrong.

[GeoffM]

Haynes manual for A/C and heating calls for 25-35 for low side and 200 for high side.

It sounds to me your system is undercharged, still. But, I could be wrong.

What page is that on? Last I checked it just said consult with a certified ac system professional.
Similar to trying to fix anything srs related.

[oyajicool]

Haynes manual number 10425, "Haynes Techbook, Automotive heating & Air Conditioning".

[Losiracer2]

This is the guide from my helms manual for a 1990 accord. Its for R12 refrigerant though, R134a will be different



I just put a new Hadsys RC-17S (took awhile to find one for a good price, ~175 shipped off ebay) remanufactured compressor in my 93 Accord EX and charged it up with R12 and I'm getting 28 degree center vent temperatures when revving up to 1500 rpm, and about 45 degrees at idle. Couldn't be happier. I really didn't go by the pressure temperature chart though, I knew total capacity was 28-30oz, so I put both 14 oz cans in and some of a 12 oz can I had until my temps got cold enough.

I ended up with 50 psi on the low side and about 175 on the high side with about a 97-100 degree ambient.

[GeoffM]

I work at Denso, and we have like 100 of those ac machines.
I just asked the right guy, and he did it for me.

I had the correct pressures, but not enough of the right stuff.

Something like .8 lbs, when I needed 1.7 lbs (Refrigerant)

We also confirmed what I thought was wrong, there was a TON of oil in there.
The canister on his machine was empty when we started, and almost full when
we finished. The foam caused it to overflow.

Still not working, but I think we've narrowed it down to either the AC thermostat
or the pressure switch. I was able to force the compressor on and make it cold
before, so I always have that option!

(I'm headed on a 11 day road trip in less than a week, I want to make sure it works)

[Stoner51]

My low side pressure is somewhere around 28-40. Your high side pressure will vary depending on the outside temperature. I think my high side is somewhere between 180-230 depending on the temp

The pressure switch will cut off the compressor if the pressure gets above 240. I think. Maybe 260.

Also when you shut the car off the system will level out both aides will be closer to the same If that makes sense. Or at least that's what mine does

When I filled mine it took 2 cans of r134. And my ac is cold as shit. It blows 44 at 100 deg outside.

Steve