A/C needs a charge

[Burning oil]

Its snowing in my truck

Got it all finished up a couple hours ago.
Went with VOV, esther oil, 1.5" thick condenser, new dryer, ajustable cycling switch.
Flushed all the hoses and evap. PO had put a dye in it and it looked like antifreeze. I flushed it until everything came out clear. Evac for 1 hour then charged system after making sure it held a vacuum.
It blows very cold now Seems like it got real cold real fast, is that because of the VOV?
I need to replace the engine oil cooler next. (leaking hose)

 

[Acesneights1]

Ughhh. Tracer dye. It's gotten better but 20 yrs ago if a system came into our shop with that stuff my father turned them away.

 

[WarWagon]

Yes, the VOV makes idle AC temps COLD! As close to an expansion valve type system as you can get without having one.

adjustable cycling switch: Make sure on the R134a pressure gauge set that the temperature of the R134a by pressure is not below or close to 32 degrees. Rev it up to 2K RPM, the ideal compressor RPM and be sure the clutch kicks out before 32 degrees. Otherwise the evaporator will become a chunk of ice and restrict airflow. Your guages should have a temperature reading otherwise do a pressure temp conversion from a chart.

Pressure of R134a = temperature of it: No Questions Asked. Yes your condenser can hit 160 degrees and stay there for 1 min as the R134a cools down. This is why you cut AC before the hill as the condenser takes time to cool down because the gas is still condensing even after the compressor has stopped...

 

[Burning oil]

OK thanks, I'll throw the gauges back on and do that test.

 

[Missy Good Wench]

If the clutch is cycling a lot and the vent air temp is cool and not cold, connect the gauges and then with the system on high, slowly add refrigerant until the low side gauge starts to dip down into the low 40's and the clutch cycles more slowly.

Check the vent air temp, wen it is cold you close enough.

Too much 134 will cause the compressor to STALL due to overcharge.

As mentioned, if the thing is completely dead, suck it down to 29" HG with a vac pump for about 30 minutes after it reaches max vacuum hold for the 30 minutes.

Replacing the accumulator is a good thing as the desicant bag will be full of moisture.

Excess moisture can get loose and freeze up the orifice tube causing a blockage of refrigerant flow.

I have done a lot of auto HVAC work over the years and R12 and R134 are fairly forgiving.

Get them close and your good to go. Better to be slightly low than have too much charge though.

A tad low can go almost unnoticed but too much will either lock the compressor or cause the thing to warm up.

Missy

 

[SfcJones]

I use nitrogen to clean out the lines, never had as problem as I thought using compressed air would introduce moisture.

 

[WarWagon]

I disagree on going low.

Per the VOV link given way back in this thread...
The systems operate in a flooded mode on the evaporator. This improves cooling as there are no hot spots in the evaporator. It also pulls the oil out of the evaporator. The flooded mode means liquid freon comes out of the evaporator. That liquid freon is pulling oil with it.

Your outlet temps are the coldest when the system is low. (I did not say best cooling just coldest temp.) But it reaches a critical point where liquid freon quits coming out of the evaporator and starves the compressor for oil... then you can get a burned up compressor.

The accumulator can hold ~1/2 pound of extra freon. The compressor shaft seal leaks by design to oil itself. So it is better to error slightly on the high side as it will leak down. Best to be exact by weight.

nitrogen is a good idea. In any case your compressed air source needs to have a water separator on it. Make sure you turn off the auto air tool oilier...

 

[Acesneights1]

The seal better not be leaking on the front of the compressor. Overcharging will ruin it. Go ahead load er up and see what happens. Take pics.

 

[WarWagon]

The seal better not be leaking on the front of the compressor. Overcharging will ruin it. Go ahead load er up and see what happens. Take pics.

I don't mean to an extreme for either item.

Where did my freon go over the past few years in a non-leaking system? Hoses and the compressor seal.

Over/under charge is at the forgiveness of the system. Accumulators main purpose is to separate and evaporate the liquid from the mixture coming out of the evaporator because we know compressors can't compress liquid...

 

[Acesneights1]

The front seal on a compressor will only very slightly leak briefly IF it's dry. It will not leak enough to release an overcharged system. A properly sealed system goes many years before needing a recharge and generall there is a leak but sometimes not bad enough to fix but it should not leak. That is why on systems that don't cycle with the defroster the a/c should be turned on once in awhile in the off season to keep the seals wet.