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A/C Question 90 K5

You are still in the ballpark as to weight. Only 3.7 oz over the original R12 charge. I suspect that the new evaporator holds more than stock.
With home ACs, you look for a 20 degree differential. In other words, with 90 degree air going in, you want 70 degree air coming out.
Note: That is the temp of the air going into the evaporator, not the outside air.
Auto ACs can run a higher differential.
I would take it around the block to see what the inside temps do, since an AC will usually do better when the airflow is increased over the condenser.
You will probably need a small amount more gas. As long as the high side pressure stays sane, and you do not get any frost on the output side of the evaporator you should be fine.
The main two dangers with gassing are too much high side pressure which can blow hoses or damage the compressor. Plus liquid freon getting to the compressor, which will destroy it really quick.
If liquid is getting out of the evaporator, you will see frost on the line going to the compressor. Heavy sweating is OK, and you should see some when the air in the cab starts to cool off.
 
My wife's truck (RAM) has the fan on the condenser occasionally and acts the same way. cycles. Pouring water on the condenser would be able to tell you if you're getting enough cooling. Did you use the factory condenser or an aftermarket - too lazy to look. That could affect the amount of Freon needed also.
 
bypass the heater hoses under the hood for summer time use, it sucks, but it's something I had to do, due to water still getting in and through the heater core, adding a bit of heat to the vents. Blend doors don't quite close all the way, I had a heater control vacuum valve on mine, others say they aren't installed on these trucks, I dunno, mine did. I just rerouted the heater hoses from the rear of the intake, back up to the radiator.
 
Fan is in place with shroud, I have not driven it as of yet, I will check the evaporator line tonight. I do know the accumulator is sweating
 
Well that's a good sign. It's possible your blower is really good, which provides better cooling, but at higher vent temps. If it cools well while driving, you know to look at the fan clutch.
 
so today's numbers were at about 35 low side and 225 high side, when I sprayed the hose water on the condenser and both pressures dropped and continued to drop until the fan clutch kicked out at about 23lbs low and 150 high side.

I am not sure what this is telling me.

The vent duct air was at 52 today at idle.

I have not driven the truck yet, waiting on plates and insurance...
 
The water test is suggesting more airflow would help. Is the new condenser as big as the old or is there a gap ato both sides? With a stock sized one you can fill the gaps at the sides, but that's only a marginal improvement. Sometimes those clutches just don't grab much. I've heard of an HD version of some kind. When you shut off the engine hot, does the clutch feel tight?

It's possible that it works fine and in the road it will be OK. The sweating receiver implies your charge is at least close. And you're getting like 40 degree drop.

It is usually worth pulling the glove box to check the blend door and make sure it closes all the way to cold. You can search here about clip problems. Even a great A/C cools mediocre when mixed with heat.
 
52 degree air is not bad at idle. Once you get it roadworthy, the increased air flow through the condenser and compressor speed will probably bring that down.
Plus as the inside air gets colder so will the air out the vents.
 
There is a flapper down by the passenger's feet - where the lower vent used to be in older trucks. That flapper is actuated by a vacuum can. If you pull off the plastic kick panel on the side you can see if it works or not. Not uncommon for the diaphragm or a vacuum line to fail. It's all original and all working on mine, FWIW.
 
Curios to know if there is an electro/mechanical replacement for the vacuum operated diaphragm, or some way to add a manual lever like way back in the old days with the fresh air vents. I'm just curious because I noticed the ball shaped vacuum accumulator for my 1985 K5 has the nipples broken off. I am considering whether it is worth trying to replace all the OE parts and draw down and converting/recharge to R134-A (system is open with unknown factors right now) or converting to a Vintage Air system, as I have heard they actually work better than the original systems. I'm doing an LS swap so I was thinking the VA system is probably the easiest option since I am going to have to do a little customization with the hoses and the connection to the LS AC Compressor anyways, with the added benefit of creating a little more space in the engine compartment.
 
There's actually 2 flapper doors, one at the passenger feet and one at the right side cowl. Max mode (recirc) cowl valve closes outside air but is mediocre at sealing. While the flapper at the feet opens.
 
See I need to take that cowl screen off and clean it out. There is a terrible smell coming from the front of the Jimmy and I am pretty sure it has something to do with trapped critters and that whole flapper door setup, and that is also a reason I am thinking about just ditching it all and swapping in the Vintage Air.
 
A. Put the vehicle in the shade.
B. Put a large fan in front of the radiator.
C. Run engine at 1500 rpm.
D. Close all windows.
E. Set A/C control to 'recirc' and high fan.
F. Put thermometer in center vent and run for 5-8 min.

Vent temp should read 37-45 degrees with no clutch cycling and the proper pressures.
 
1) are you using a low pressure switch for 134a?

2) there should be an adjuster screw inside the low pressure switch to adjust your cycling pressure.
 
Turn it "in" (CW) to raise the cut-out pressure (warmer). Turn it "out" (CCW) to lower the cut-out pressure (cooler). The goal is to cycle out just above where the evap freezes. Temp and pressure are the same thing - you'll see them both printed on your gauges. I've had mine set below freezing and cooling is worse. Airflow gets lower and lower as the evap gets completely plugged. Then when you shut it off, a bunch of water runs out and airflow is restored.
 
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