New guy with an AC question

[Stresst]

see if you can bump it up another 5 psi on the first number to ballpark it and be absolutely sure you valve cap is clean inside with no damage inside either and do not over-tighten it. Call your self good for now and keep an eye out for leaks. Always run your compressor for a about 10 minutes each week to keep the system in good shape.

---------- Post added at 06:47 PM ---------- Previous post was at 06:36 PM ----------

BTW your cycling rate is in a good area as well.

---------- Post added at 06:47 PM ---------- Previous post was at 06:47 PM ----------

you should get about 8 a minute while idling.

---------- Post added at 06:51 PM ---------- Previous post was at 06:47 PM ----------

If you are not cycling about that much when idling you charge may be getting low. If it stays on continuously not matter how hot it is, that will be the sign that it is time to go back in and find the leak

Dont mean to hijack but I have to ask, the compressor is supposed to go on and off? As far as I know mine stays on. I will have to check tomorrow. When you say 8 minutes, run for 8 minutes? Then how long off?

 

[gpracer1]

There are only three reasons for an AC system to cycle.

1. The system is low on freon and the low pressure due to lack of freon is tripping the low pressure switch. It does this to protect the compressor from damage (no freon, no oil transfer). Also if there is an obstruction in the line this can happen (clogged orifice or accumulator came apart).

2. The system is charged correctly. The outside and inside of the cab temps are cool enough to make the evap so cold that it cycles off to protect the compressor from damage due to the evap freezing and having liquid freon enter / reach the compressor. It will also cycle if the blower is on low, since you are not removing very much heat with low airflow and the evap gets very cold (low psi, they are directly related). Also as the rpms go higher, obviuosly the suction is greater and the low pressure drops.....its a double whammy since the compressor is also protected by high rpms.

3. The system is overcharged tripping the high pressure cutout.
The same will happen if there is not enough airflow and the high side gets to the high pressure cutout.

Of course there are a few other things like WOT and other inputs from the PCM, but that is it in a nutshell.

ASE Master tech since 91.

 

[SunlitComet]

I think you have that part backwards.
At idle if it is hot out and the system is charged correctly and on high blower.....it will never cycle. At idle the low side will be around ~32-45 psi depending on the ambient and in-truck ambient.
If you put the blower on low, then when the evap gets cold enough, the pressure will drop to 23 and it will start cycling.

Let me clarify I was talking about inside temperature. Sorry I failed to mention that.

---------- Post added at 07:36 PM ---------- Previous post was at 07:25 PM ----------

Dont mean to hijack but I have to ask, the compressor is supposed to go on and off? As far as I know mine stays on. I will have to check tomorrow. When you say 8 minutes, run for 8 minutes? Then how long off?

I meant about 8 on/off cycles a minute.

 

[96SLE]

OK,now the compressor kicks on at around 45psi and turns off at about 25 psi.It doesn't cycle at all at idle now and it cools down to 43 degrees.I guess I'll just watch for leaks now.

 

[Stresst]

Let me clarify I was talking about inside temperature. Sorry I failed to mention that.

---------- Post added at 07:36 PM ---------- Previous post was at 07:25 PM ----------


I meant about 8 on/off cycles a minute.

What does it mean if it stay's on constantly?

I remember my naviagtor you would here it go off and on numerous times a minute and that beaotch's a/c blew cold as hell!

 

[96SLE]

I drove the truck about 75 miles today with the air on and I think I see why the dealer said the compressor is bad.It has had greasy looking areas with a slight greenish tint on it since I bought the truck but I didnt know what it was.I always thought it was just dirty and tarnishing.Now it looks like the green is getting brighter.Is that freon leaking from the body of the compressor itself?It is still cooling really well but this doesn't look right.

 

[SunlitComet]

Your are leaking freon still and cycling is effected again. You have found your leak I think. The dirt is is most likely gunk building up on the oil leaking out and the green Is most likely a leak detection dye or corrosion. If I am correct plan on changing your compressor. Get in a new accumulator/drier in there as well and recharge. Without needed(and probably borrowable tools for part store) cost should be under $400 in parts.

 

[N813]

Welcome again is this the connector up top on clutch unit or at the rear of compressor.

If up front lets start out by checking out your compressor relay in the under hood block. If you probe for power in the relay socket you should see bat voltage on two different terminals with ignition on. They are fed by "IGNE" and "A/C comp" fuse if that is fine reinstall relay and listen to see if it clicks with engine running when a helper turns on the a/c from inside. If not ensure the light green wire on back of hvac control head puts out battery voltage when a/c is selected and fan is on. Start with that. Also do you have any info on the refrigerant charge status ?

This is a long shot, based on how old this thread is. I'm hopeful you're still out here.

My light green wire (#10) on back of HVAC control has no power. No blown fuses.
Only the brown wire (#5) has power.

Where does that light green wire come out at?