AC Clutch Continually Cycles

[MrMarty51]

I have, in the past, searched the internet for an answer to this question.
How frequently should the AC clutch kick on then off.
If this is not normal, what can cause such a situation ?
I have installed a new clutch, temperature from the bilevel duct is at 44 degrees.
I used one of those single hose applicators that a can screws onto, then pull the trigger to charge the system.
When the compressor clutch is engaged the pressure drops to barely in the low range on the gauge, pressure climbs then clutch kicks back in and pressure drops to low range again.
I run the engine at the 1500 RPM range with both PTO option switches turned on to ground.
Tried holding the can in a container of very hot water and cant seem to get the system to accept more freon.
Is this a normal condition to have the AC clutch engaging and disengaging several times is a minute ?

 

[MrMarty51]

Oh yes, I forgot. I have that Duramax Electro Viscous fan wired so that when the AC compressor kicks on, the fan also kicks in.
I have a light on the 3 gauge cluster that illuminates when the EV Fan is turned on.

 

[Will L.]

You need a set of gauges, and the chart for your type of refrigerant.

Low charge can do it, so can high charge.

 

[Rockabillyrat]

Agreed, you need to be able to watch the high pressure side. It might be kicking the clutch off via the high pressure switch. Also did you pull the system into a vacuum before you charged it? Air in the system can cause pressure issues.

 

[MrMarty51]

Nope. Just pumped a can of freon into it.
I do have the hoses, gauges and manifold.
Been so long since I messed with AC that I dont remember much about it.
I did have the grill removed off the front of the truck.
Temperature Difference between the two pipes into the condenser was about 8 degrees.
When the compressor was running it would pull the gauge on that simple setup not too far into the low charge range.
When the clutch would kick out it would climb into the upper range of the charged state.
I’ll wait until I get back from this journey over to the cabin then get out the manifold setup and pull a vacuum on it and see where that goes.

 

[dbrannon79]

What I have learned, the first thing to do is after the truck has been sitting for a minimum of 30 minutes off, longer is better so there is less heat radiating from the engine when is was last running, connect the gauge manifold both high and low sides. don't start the engine or anything yet.

take note of both gauges and their readings. make sure both are equal too. then look up the static pressure temp chart for 134a and compare.
I use a temp gun at various places like the accumulator, condenser, and outside air temp and use the average from the three. take that temp and find it on the chart. the chart will tell you what the pressure should be at full charge. if your gauges are low then the system has a low charge and vice versa.

on mine, I just did this yesterday afternoon finding that I was about 40psi lower that the chart said it should be. after adding one can, taking another pressure reading today and it's only about 15ish psi lower that the chart. In theory I could add a little more 134a, but right now it's cooling good enough as long as I can keep the fan clutch working in this 100 degree heat!

 

[dbrannon79]

After verifying the system has a full or close to full charge, then procede to start it up, fans on max, dial temp in dash vent and watch the gauges as the cab cools down. from there you'll see if there is a blockage or can fine tune adding slightly more or less 134a.

 

[MrMarty51]

After verifying the system has a full or close to full charge, then procede to start it up, fans on max, dial temp in dash vent and watch the gauges as the cab cools down. from there you'll see if there is a blockage or can fine tune adding slightly more or less 134a.

Thank You very much for the information.
I’ll be gone off to the cabin for a few days. High temps in the low 70s so I wont be running the AC.
I will verify all temps and pressures after I get back.
I’m still curious, does the compressor clutch on Your truck kick on and off while the engine is running and AC engaged ?

 

[dbrannon79]

the compressor does cycle but not more than maybe 5-6 times a minute in cooler mornings, in the afternoon's when the temps are up in the 95+ it seems to continually run. I know my compressor has a slow leak and just the other day I noticed it's beginning to have knocking noises. I will be needing to replace it soon. I wish I could find a sanden replacement for it or maybe a 6.5 bracket setup for the 96-97+ engines so I can use a better one instead of this pancake compressor.

 

[Will L.]

I have often wondered if there is a more modern compressor from a different car/truck that would be a better choice. These older GM’s have a horrible track record. Have to do a compressor, modify mount and have two normal hoses made instead of the funky thing gm uses with 2 in 1 hose.

 

[MrMarty51]

Okay. Finally getting back to the AC conditions.
The ambient temp, according to weather apps is about 75 degrees F.
When the AC is set on the fresh air mode the compressor clutch does not cycle.

Engine idled up to 1100 RPMs and AC set on MAX and fan speed on high.

And the thermometer.

 

[MrMarty51]

I sent the videos to a friend that is more AC savvy than myself.
He stopped over at My house.
Watched the compressor cycle several times and said it is working most excellent. What do You think is the matter ?
I responded that I was wondering if the compressor cycling so often is normal. He said yes, thats just how they function.
Okay, I guess it is all good.
I am going to get that dual sided high pressure switch and install it though.

 

[dbrannon79]

looking at your pressures and vent temps I would think you are just a smigid low on 134. maybe just a few ounces but you can't go off of the weather app. you need to get the actual outside temp around your truck.

connect the gauges and take a reading on both gauges without starting the truck, both gauges should show equal pressures. post that reading along with having your temp gauge outside, post the temp reading too. then check the 134A temp / pressure chart to see if you are low or high this is the first step when checking an ac system. static pressure check is what they call it.