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'85 Factory AC System -- How to Repair

ford4wd08

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I wonder if it wouldn't hurt to replace the evap core... they are only about $60, I feel like they get kinda fragile over time and probably plugged up full of leaves and stuff unless you have cleaned it out. Easier to get to on your truck too since you don't have the intake tube, coil pack and a ton of wiring in the way.

The more AC work I do, the more I feel like replacing everything is the way to go.
You're right. I just went ahead and ordered it too.

I have doubts I'll be able to get the old drier assembly off of it anyhow without some sort of damage.
 


Shran

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I can verify the evap coil gets plugged up. It's more like a mud from the condensation on the coil combined with dirt from outside. I had a old 1980 f150 and it always had marginal heat output, even with a new heater core and thermostat. I pull the evap coil out and cleaned it. what a mess. Also got a pile of pencils, pens, wrist watches and junk that had fell down in from the defroster vents. Once I cleaned that A/C coil out, I had tons of heat in the cab.
Yep sounds about right. The one I just replaced in my Explorer had only been in there for a few years and it was 1/4 full of small leaves and cottonwood tree cotton. It's even parked inside most of the time!!!
 

ford4wd08

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@Shran

Do you think I'll need a new pressure switch on the drier? Is there a way to test it?
 

Shran

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Might not hurt. I used a NOS motorcraft one from eBay on mine and it was only like $15. I discovered that it was bad only because I could hear nitrogen leaking out of the electrical connector. Probably wouldn't have replaced it otherwise but if was cheap either way.
 

ford4wd08

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Might not hurt. I used a NOS motorcraft one from eBay on mine and it was only like $15. I discovered that it was bad only because I could hear nitrogen leaking out of the electrical connector. Probably wouldn't have replaced it otherwise but if was cheap either way.
I went ahead and ordered one. I don't want to be in the middle of charging the system and that be the reason the compressor won't cycle.
 

ford4wd08

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I assume I'll need adapters for the high and low pressure fittings from R12 to R134A right? Any adapters better than the others?
 

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If memory serves, from back when I did my '90 B2, you just need one adapter on the low side, to charge the system. I'm not aware of any one brand being better than another.
 

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One low side adapter is the minimum required to get it going. If you want to put gauges on it and monitor the high side as well as pull a vacuum on the high and low sides at the same time (faster to do this) then you then both adapters. The retro fit kits come with the adapters.
 

ford4wd08

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So, circling back to this.

I installed a new evap, condenser, drier, orifice tube, compressor, low pressure switch, a new AC v belt, and all new o-rings over the long weekend. I did end up buying the R134A adapter set for high and low side.

I ended up reusing my 3 original hoses because they were in good shape, but I made sure to flush them good with solvent.

It really wasn't too bad of a job.

Then I vacuumed it down and everything seemed to hold well. So I charged it up. The sticker for R12 said a capacity of 2 lbs 12 oz (48 oz total). Mistake one I made when converting it to R134A was not realizing it should take less of a charge. Mistake two I made was not getting the condenser hose from the compressor fully seated behind the spring clip. So I over charged it, gave it a little throttle and it blew the hose off...... Luckily no one was hurt and nothing got damaged. I did loose my new refrigerant.

So after I changed my shorts, I tried again after I was 100% sure all spring clips were seated correctly. I didn't get the cooling and cycling of the compressor I thought I should.

So I stopped before I tore something up (hard lesson to learn). Called my friend with the AC machine (he repairs and sells auto shop equipment as a business with his dad) and asked if he had time this weekend to look at it.

His office/shop is about 7 mins from my house, so I drove over yesterday afternoon and we hooked it up and sucked it back down. Then put it on vaccum for a bit.

I told him I thought my new condenser coil that was stacked plate design probably had less capacity for freon then my older tube and fin style, so he recommended starting with a smaller charge. We tried 2 lbs and still didn't get the pressures and cycling of compressor that we thought would be ok. Sucked it down again and charge it with 1.5 lbs. Then we started getting compressor cycling and pressure that made sense. We decided to leave it like it is for now and recheck it again when the temps get warmer down here in the south.

It was cooling great when I drove it around some yesterday.

So final thoughts, if you change to a newer style condenser, it likely won't have the same capacity as before. Also, R134A should be 80-90% weight charge of R12. And finally, have a friend with an AC machine, it definitely makes trouble shooting and recovering and charging a system, much, much easier. 😂

I also attached a picture of the old condenser vs the new one.
 

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RobbieD

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Great work! (y)

That's good information on the condenser difference and charge weight.
 

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It may have been mentioned in this thread before, but when you change to the different gas, sometimes you can make the cycling more in your favor by tweaking the low pressure switch. It has an adjustment screw right in the middle you can see when you unplug the electrical connector.

For instance if you think you have plenty of gas in it, but it still tends to short cycle more that you would like, you can tweak the pressure switch to reduce the frequency of the cycling and keep the compressor running longer. This will make it cool better. You can overdo it, and the evap core will then become a big block of ice.
 

ford4wd08

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It may have been mentioned in this thread before, but when you change to the different gas, sometimes you can make the cycling more in your favor by tweaking the low pressure switch. It has an adjustment screw right in the middle you can see when you unplug the electrical connector.

For instance if you think you have plenty of gas in it, but it still tends to short cycle more that you would like, you can tweak the pressure switch to reduce the frequency of the cycling and keep the compressor running longer. This will make it cool better. You can overdo it, and the evap core will then become a big block of ice.
I did not know that. Thank you for bringing that up.

I'll have to try that and see what it does.

This is why I love this forum!
 

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I'm wondering if you can check to see if it has Freon in it still. If so maybe you can go the cheap route, see if you can get a can of R-12 and charge it up or check to see if it has Freon in it.. I'd seriously do that first.

There are cans of R-12 for sale on Ebay. Some affordable too. They sell the charging hose too for the R12.
 

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franklin2

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I'm wondering if you can check to see if it has Freon in it still. If so maybe you can go the cheap route, see if you can get a can of R-12 and charge it up or check to see if it has Freon in it.. I'd seriously do that first.

There are cans of R-12 for sale on Ebay. Some affordable too. They sell the charging hose too for the R12.
I believe none of those are true r12. They are blends of other refrigerants.
 

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Here is what it really is. Some call it r12a. Some call it HC-12a


HC-12a, also called ES-12a, OZ-12a, DURACOOL 12a[1] and Hydrocarbon Blend B, is a "drop-in" replacement refrigerant for Freon-12 and to a lesser extent, R-134a. HC-12a is a mixture of hydrocarbons, specifically propane (R-290) and isobutane (R-600a), and is therefore considered nearly non-ozone-depleting when compared to dichlorodifluoromethane (R-12, Freon-12) or 1,1,1,2-tetrafluoroethane (R-134a). The mixture can be used in refrigeration systems designed for R-12. HC-12a provides better cooling than an R-12 system retrofitted to R-134a, with much greater energy efficiency as well. Unlike R-134a, HC-12a is completely compatible with the hoses and oils used in R-12 systems, making the conversion much easier to accomplish. HC-12a is also patent-free due to its non-synthetic nature.

Because of its high flammability, it is unacceptable to replace R-12 with HC-12a in the United States.[2][3] Thus its use in public transport vehicles is illegal in the United States since 1990.[4][5]

 

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