A/C Temperature

I recently installed an A/C kit in my 96 Chevy k1500. 4x4 383 for what it matters. I have highway speed temperatures of 55-60 degrees and idle speed temperatures of 63-70. I will add that this truck has a 3 inch body lift and headers (assuming the heat difference and air gaps on the fenders hinder the engine pay temp). The fan shroud is currently cut for the fan clutch to clear it. I plan on modifying the shroud this weekend with different hardware and adding an 11 blade heavy duty fan clutch to this as recommended by another member. I will also add that the engine is currently untuned, and I am unaware of the effect that may have on the AC if any at all. I guess my question becomes does tuning affect the AC relative to RPMs and does this fan shroud as it sits have an impact on the system?

The tuning of the engine and the fan shroud do not have that much influence over the AC system. If at highway speed you are only getting 55 to 60° out of your vents, the problem lies somewhere in the AC system. You should get a set of manifold gauges and see where your high and low pressures are at. It's possible you just need a refrigerant refill.

Yup see what the pressures are for sure!

PS…I love all of these AC threads lol. I’m battling it too

JohnZ71 said:

Yup see what the pressures are for sure!

PS…I love all of these AC threads lol. I’m battling it too

Click to expand...

Haha, man it's annoying.

Das Hatt said:

The tuning of the engine and the fan shroud do not have that much influence over the AC system. If at highway speed you are only getting 55 to 60° out of your vents, the problem lies somewhere in the AC system. You should get a set of manifold gauges and see where your high and low pressures are at. It's possible you just need a refrigerant refill.

Click to expand...

The evaporator core in this truck is about 2 years old if that. The ENTIRE system has been replaced... Compressor, condenser, accumulator, and orfice tube. All lines have been flushed.

Das Hatt said:

The tuning of the engine and the fan shroud do not have that much influence over the AC system. If at highway speed you are only getting 55 to 60° out of your vents, the problem lies somewhere in the AC system. You should get a set of manifold gauges and see where your high and low pressures are at. It's possible you just need a refrigerant refill.

Click to expand...

Are you saying there a chance that my Freon level is low after just doing the rebuild?

Could be refrigerant level. I would look at the cycling switch as I have found the to be a big problem area in these trucks and the early GMT800. They will partially fail and start cutting the compressor out as early as 60 psi instead of low 20s. My buddies 2003 1500HD was cutting out at 60 psi a couple of summers ago when he was fighting a cooling issue. Those trucks use the same junk switch. I replace the small fixed pressure switch with the older style adjustable switch. The older style switch has contacts rated at 20 amps because they carried the a/c clutch coil current thus last fairly indefinitely especially in a vortec era truck that uses an ac relay to control the clutch.

L31MaxExpress said:

Could be refrigerant level. I would look at the cycling switch as I have found the to be a big problem area in these trucks and the early GMT800. They will partially fail and start cutting the compressor out as early as 60 psi instead of low 20s. My buddies 2003 1500HD was cutting out at 60 psi a couple of summers ago when he was fighting a cooling issue. Those trucks use the same junk switch. I replace the small fixed pressure switch with the older style adjustable switch. The older style switch has contacts rated at 20 amps because they carried the a/c clutch coil current thus last fairly indefinitely especially in a vortec era truck that uses an ac relay to control the clutch.

Click to expand...

Man I couldn't wait for your reply! You're the guru bro. I believe I got the part numbers from on a different thread. I will be checking head pressures here soon as I work at an auto repair shop. I am not familiar with the adjustable switches. Would you happen to have a thread/right up in this?

MalcolmEatmanGoode said:

Man I couldn't wait for your reply! You're the guru bro. I believe I got the part numbers from on a different thread. I will be checking head pressures here soon as I work at an auto repair shop. I am not familiar with the adjustable switches. Would you happen to have a thread/right up in this?

Click to expand...

I do not have a thread on it, but it is as straight forward as it can be to swap out. The part numbers mentioned are Four Seasons which also cross straight across to Oreilly's Murray line. Can save a few bucks through their commercial account discount compared to buying online. Generally they are stocked at the hub level if not in your local store meaning you can generally get them same day. I luck out to have a mega hub a mile from me in DFW. The connector is not polarity sensitive. Cut the OE connector off and splice the new connector on. I used solder sleeves and added some extra tape over the splices then split loomed it. CCW on the adjustment screw between the terminals with screw facing you lowers the cutout pressure making the compressor run longer and making the evaporator colder. Out of the box I generally turn the screw 1/2 turn CCW and then test. No freeze up you can go another 1/4 turn and repeat. When the core starts freezing you will experience lack of airflow through the vents, back of 1/4 turn CW and retest. As soon as it stops the freeze up you are as cold as the system can operate at.

Post in thread 'AC overhaul - Compressor upgrade? Condensor?' https://www.gmt400.com/threads/ac-overhaul-compressor-upgrade-condensor.68374/post-1430394

If you do not have the 11 bladed fan already in your posession check out this thread. Properly fitting shroud will make a big difference in idle cooling and can make a difference driving around as well. In extreme heat the clutch fan will likely engage at times even at highway speeds which does increase airflow through the cooling stack.

The only way my Express van stays cool on a 115F day is with the clutch fan coming on and off as needed even at 85 mph. The EV clutch I run now does an excellent job variably controlling the fan speed as needed for just the right amount of cooling to keep the engine and transmission cool and airflow across the condenser to keep the ac pressures where they should be. With the P59 running the EV clutch I can monitor both the PWM signal to the clutch and the fan RPM. It varies anywhere between 15% and 85% engagement, turning the fan anywhere between 400 rpm and 3,000 rpm.