Last year i decided it was time to add an AC unit to my truck, an 87 4.9 that purchased in nor cal. Its a runner and came from the factory with a heater box only.

After doing some research I got some good feedback about AMA and decided to go with them for the parts i needed. A grand later i got a big box with everything I needed and got it all installed in under three hours, on a late afternoon.

The next day I took to a shop that did the vacuuming and charging of the system. All of this happened towards the end of the summer and the kit was never tested until the heat waves came this year.

The AC left so much to be desired and yet i knew that there was so much potential in this system. Disappointed as I was with an ac system that only cooled to about 70 on a 110 degree day i decided something had ti be done. I knew that in the early mornings on my way to work the ac would cool to 60-65 degrees, but that was it.

I then decided to go to my local Orilleys auto parts store and get a can of r134a and a gauge for the low side. When checked the pressure it was at 55psi on the lowside and couldnt believe that it was not low on freon. Everything i had told me that this was the problem, and not inly that but the directions for the gauge said for anything above 100 degrees the LP side should be at 55. I asked myself how can it be that its not cooling then?

Well i started looking into what you all are saying on here and reading up on relationships between ambient temps and the different pressures that we get with professional gauges.

Luckily i stumbled upon a link that to a chart that ama put out for their systems and where they believe the low side pressures should be. Let me be the first to say they were right!

55psi is what my low side was and thats what the directions on the gauge i bought said it should be at as well. So, I believe the mechanic that filled the system did so based on what he was taught. In theory 55 psi may be correct, but in my case it was too high.

So what I did was I relieved some of the PSI on the lowside. I took it down to 25psi because of the outside temps at that particular time of the day. I did this because of what is indicated here.



Mind you for an entire year I had been only seen a temp gauge get down to 65ish... By dropping the pressure down this low the compressor started cycling pretty fast. Which it had never done before, so i knew i had gone too low. Max AC on and vents blasting I started adding freon a bit at a time and each time i closed the freon can I would check on this gauge I bought at petco for ten bucks.



Its an awesome gauge and tells me what the temp is to the nearest tenth of a degree; plus it seems to be very sensitive to changes in temperature.

After each time I added freon and went to look at the gauge I could see the temp dropping lower and lower. Sadly, the 12oz can finally went empty and I had to stop at the temp you can see in the picture. Im going to take the can in and get my ten bucks back so that I can buy another and hopefully get it down into the thirties at idle.

This ackit from ama/ackits.com was the best choice I could have made. I was disappointed initially but that had nothing to do with the kit and everything to do with the mechanic that didnt care much to get things dialed in. It works just like the ac unit from the ford factory and I would recommend this kit to anybody thats thinking of buying one. Just make sure your around when its getting charged and take a good temp probe with you so that you you know the mechanic is doing things right. It also wouldnt hurt to write down the ambient temps and pressure readings you get while its at the shop for future reference

 

you stumbled on the best kept secret... if you've followed any of my AC post her thats one thing I've said ONLY to fill the AC system until the compressor stops cycling... the lower the pressure the colder it will get....

good job

 

Thank you! Your post fixed this problem I had!! Hats off to you!

 

Hey DR Bowtie, i used your method for getting the ac to cool more but i think i could get it to cool further if i connect the test lamp as you mentioned.

Do u have any any more specific directions on how i can go about doing this? Is it just attaching a test lamp to the switched wire at the LPS and then grounding the other side?

Pardon the dumb question, i just dont to cause the compressor to burn up....

 

yep thats how you do it... I just grounded the other side of the test lamp wire to the underside of the dash....

I actually got some little colored lights and mounted them in my dash where the blank switch pad is... I also have lights on the Fans... I have a red light on the AC Compressor and blue for the fans...

All the test light is for is just showing when the compressor has power applied to the clutch... it also has 12v wire running from the switch and the other side is grounded...

 

When on the road with the test light my compressor stays on for 20 seconds and goes off for 10 once it reaches its coldest point. How often was yours cycling?

On til 41 degrees and then off until it got to 43. Im thinking it'll get lower if I break into another can now that im using the test lamp.

( I just went out and shook the last can i had and noticed there was a bit left so i added it and this time the cycles on the road were taking it down to 39and 41 at the highest.)