ac question

[CarterCat]

hello to all. First time posting. I have searched but can not find out what the electrical coil thing inside the evaporator box is and what it does.
I flushed the ac system on my 1989 f250, replaced orifice tube and vacuumed, everything was good, so I started adding the charge and the vent temp dropped to around 41 degs.
I thought that is was good then the temp started climbing back up to around 60. now it will not cool below 60 to 70 depending on the outside temp. What did I do wrong? Could this electrical device inside of the box be causing me the grief? Thanks for your help.

 

[gnathv]

The coil thing is the resistor for your fan speeds. It's mounted there so the air moving across cools it.
If your vent temp was at 41 and you continued to add freon and it went to 60, you have overcharged it.
Lose some freon. It's an 89, is it r-12 or converted to r-134?

 

[CarterCat]

It has been converted over to R134, failed to mention that I also replaced the dryer. How much of R134 does it need? I'm using 12oz cans.
The dryer that was replaced read that it took 3lbs 4 ozs of R12, but I don't know how much R134 to use.
Thanks

 

[cpdenton]

In my opinion, the best way to charge the system is to check actual pressures.

Do you have gauges? I always fill until I have about 42 PSI on the low side with the a/c compressor running and the fan pulling good air across the condenser.

 

[CarterCat]

Yes, I have gauges. They were reading 48 low 250 high ambient temp approx. 87.
Did I overcharge it?
The lines and dryer frosted up, I switched the fan to high and the frost started to melt and it never got cold again.
I have checked the system and can find no blockages. I removed both coils and cleaned them inside and out to make sure that they were clean.
Compressor seems to run fine, no noises,etc.
Can anyone tell me how much R134 to put back in?

 

[gnathv]

Yes, I have gauges. They were reading 48 low 250 high ambient temp approx. 87.
Did I overcharge it?
The lines and dryer frosted up, I switched the fan to high and the frost started to melt and it never got cold again.
I have checked the system and can find no blockages. I removed both coils and cleaned them inside and out to make sure that they were clean.
Compressor seems to run fine, no noises,etc.
Can anyone tell me how much R134 to put back in?

About 80% 134. 38 oz.

Did you replace or clean orifice tube.

Gauges are good but digital thermometer helps get it right. Just an oz makes a difference. Are you going to blow the charge and start over (which isn't necessary) or let a little out at a time until temp drops? Run fan on high while charging, this will insure evaporator saturation.

 

[CarterCat]

I evacuated the system, removed the condenser, orifice tube, which I replaced the first time(it's red) and evaporator and used coil cleaner on both and blew shop air through them to check for blockages. The evaporator box had some leaves inside that could hinder the flow of air so I disassembled and removed it so that I could better clean it. I'm in the process of putting it all back together and I don't want to have to do it over again. I appreciate your help. When I recharge, after pulling vacuum, I will use only three 12oz cans and see how it goes. I hate to open another can just for two ozs, but will that make a difference? Should I add any oil back for replacing the dryer and flushing out the system, minus the compressor?

 

[cpdenton]

If you are at 48 psi on the low side, you are too high already. Don't add more. Let some out until the low side pressure is at 42 or so.

 

[gnathv]

Did you flush the compressor? If you did you have no oil in your system, if you did not you have a couple of ounces in it. Your 89 with r-12 calls for 10oz of oil.
This is a chart I use.

F SERIES FULLSIZE PICKUP

1996-1997 All Engines R134a 38.00 PAG 46 7.00
1995 All Engines R134a 33.00 PAG 46 7.00
1994 All Engines R134a 32.00 PAG 46 7.00
1993 All Engines R12 44.00 Mineral 7.00
1991-1992 All Engines R12 44.00 Mineral 10.00
1986-1990 All Engines R12 52.00 Mineral 10.00

I would put in 7 oz of oil. 2 oz in evaporator, 2 oz in condenser, and the last 3 oz in compressor.
Turn compressor by hand to push it through.
I would start with 32 oz of freon and go from there. 2 oz too little of freon will be noticeable on a hot day.
It will cool but not enough to be comfortable.

 

[crash-harris]

If you have opened up the system, then you have exposed it to air, therfore contaminating the system. Sounds like you need to take it to a shop and have then connect it to the machine and purge the air from the system and refill with oil AND r134a. If you start replacing valves or tubesthen you'll have to have the system purged. I've had to do this a few times when valves and o rings in other people's vehicles had started seeping/leaking and required replacement.

 

[DaytonaBill]

Using cans makes it almost impossible to install the correct charge.

Using a A/C scale and knowing how to purge charging line is key here.

After purging charging line, using scale, install 32 ozs at first. This is for R 134A...

Using a IR thermometer, add just a little bit more until temps going into evaporator core and temps coming out of core are the same while engine is running with A/C controls set on Recirculate and high fan speed. Paint the aluminum tubes into and exiting the Evap core black. This will help the IR thermometer's accuracy.

Then check pressures. Low side should read about 25 to 35 lbs of pressure. in that range, the evap core will be between 29 to 40 degrees, depending on how well compressor is working and the amount of charge in the system.

Also, check the cutoff pressure, or the pressure the A/C cutoff occurs. This is for keeping the evaporator from turning into a solid block of ice. The cutoff pressure should be within a narrow range, that is, between 25 to 30 degrees. Ideally 28 would be best on the average, depending on your climate.

A/C work really is half easy (the replacing things part) and very tedious (the recharging with refrigerant part, with ALL of the correct tools and experience).

I feel you really have two choices to choose from here.

Do a complete hardware replacement or what the pros call a "front of firewall replacement" or "firewall forward replacement" and let the pros do the recharging, OR, learn like I did, blunder through all aspects of the hardware installation (lubing the O-rings, but NOT with PAG oil for instance), using a basting injector to measure the oil into new compressor, AFTER draining, ECT...

Then jury rig a make shift way to measure the weight of the refrigerant of your choosing (I used a Propane/Benzine blend, but that's another story...) that you install into the system.

I'm still learning, but at least I have grown to the point in which my compressor and A/C system lasts longer before I have to troubleshoot it again.

 

[79jasper]

^ Bill, any good books or sites you recommend to read up on?

Sent from my SM-T537R4 using Tapatalk

 

[DaytonaBill]

Jasper, not meaning to blow you off, but I do have a very good book but I can't remember the title... I'll go look tomorrow in storage for it and post it here, ok?

 

[79jasper]

Sounds good.

Sent from my SM-T537R4 using Tapatalk

 

[franklin2]

If you have opened up the system, then you have exposed it to air, therfore contaminating the system. Sounds like you need to take it to a shop and have then connect it to the machine and purge the air from the system and refill with oil AND r134a. If you start replacing valves or tubesthen you'll have to have the system purged. I've had to do this a few times when valves and o rings in other people's vehicles had started seeping/leaking and required replacement.

He said he put it on a vacuum pump before charging.