I need to rebuild the AC in my 1991 3.0 pickup. I will use a new Denso compressor and replace the lines and all needed parts and I-rings. My shop can fill it with R12 or R134. For the people who have converted to R-134a, how happy have you been with the new system?

 

I've rebuilt multiple A/C systems on these trucks. R-12 hands down works better. R-134a got down to about 46 degrees under the best conditions. R-12 gets to about 38 or 39.

 

That was what I needed to know. Thank you sir!

 

PO of my truck converted to R-134A and said it was not working well (he lived in AZ) & ended up finding a shop to convert it back top R-12. I'm happy he did, AC works great!

 

I will go with the R-12 and replace everything except the hard lines. They will get blown out with compressed air and new o-rings. The only part that was hard to source was the low pressure hose, but a local shop is going to fabricate me one using my metal ends.

 

I am hoping to spend some time on the AC replacement this weekend. I have a new compressor, receiver drier, condenser, evaporator, expansion valve, and high pressure and suction lines. I plan to verify the amount of mineral oil in the compressor (Denso). Their instructions said to spin it by hand, clutch down, a few times to lubricate it. Any other tips for a smooth install or things to avoid? It has no remaining freon in it. I will blow out all of the metal lines with compressed air. I have a new set of green o-rings as well and will soak them in mineral oil before installing them. I have flare wrenches for the connections. Thank you Yotatech brothers for any tips you can provide.

 

There are charts that compare the (theoretical) pressure and temperature difference of these two gasses. I don't see a substantial difference myself.

Best wishes!

 

I finally finished my AC install today. I feel like I am on top of the world. I converted to R-134A and got 39 degrees F while on the freeway. This was my first time ever, I read over;

https://forum.ih8mud.com/threads/how...unner.1210923/

https://www.yotatech.com/forums/f116...-r134a-284801/

https://www.yotatech.com/forums/f116...pickup-310891/

I went to O-reilly's to get the loaner Vacuum Pump and Set of Gauges, watched the video by Chris Fix and boom, got it second time around. First time I went through one bottle and then my low pressure AC line started leaking. I sent my hoses to coldhose.com to replace the rubber hose, it costed me $120 for the low and high pressure hose. I had bought a reman Denso Compressor and the clutch would not engage due to the low pressure from the Refrigerant bottle. I had to manually engage the clutch using a wire straight to the battery and rev the truck to 1500 RPM. Once it started taking refrigerant I reconnected the compressor to normal configuration and I was done in 40 minutes.

 

I usually start charging with the engine off. I'll open both valves until the bottle stops flowing. Once it stops flowing, I'll shut the high side valve and start the engine to charge up the rest of the way.

Also, pressures are a diagnostic tool, not to be used for measuring charge. When you are charging, you should have an evacuated and vacuumed system, then charge by weight.

 

Where did you find a condenser? I have been looking everywhere for a new one and nothing has come up, even through the vendors at my shop.

 

That is a true story my friend. I ordered a spectra and that one had a wrong connection on the receiver/dryer side. So I ordered a Denso from densoproducts and they were on back-order til who knows when. The last piece I needed was a condenser. So I just repaired my old Denso condenser (stripped male connector) and it worked.

 

I ordered the condenser and receiver drier from Jegs. They were about the only people who had one in stock. According to their website, they were shipped today.

 

R-12 is a better refrigerant than R-134 in that it will give you a bigger delta T from the hot to cold side of the system. The only draw back is that R-12 is bad for the ozone in our atmosphere which is why it had been discontinued in car manufacturing for a good many years now.

 

Also the price as well. $40(R-12) per can or $6(R134) per can. You can go to walmart and buy R134. For R-12, good luck. I've seen some on ebay, some on OfferUp. If I was allowed to go Tijuana, I would've went there to get it charged.

 

Yotatech brothers, does anyone know the proper amount of mineral oil to use in the compressor? I am replacing the evaporator, hoses, condenser, drier, expansion valve and compressor. Thanks in advance!

 

I converted to R134 but when I got the remanufactured Denso 10P13C it already came filled with mineral oil, about 100 ml and I had removed it.

Make sure you add some in your Drier.

 

R-12 does cool better, pound for pound. They had to make the R134 systems a little larger so the performance would be comparable.
I replaced all the o-rings in my system, with the exception of the compressor. I threw in some R134 to see how I did and two years later it's still going strong. I knew it was a risk to the compressor, but a new reman Denso compressor was fairly reasonable, so i took the gamble.

Side note: the amount of leaves and crap in the evap box was staggering. To get all that cleaned out justified all the work. it was more than half way filled up and restricted

 

I did some further research and came up with 7 ounces of oil and 27 ounces of freon for the system. The freon quantity checks out with the factory service manual, which calls out 24 to 28.8 ounces. The denso compressor instructions say to drain the old compressor and measure the quantity of oil. Next, they want me to drain the new compressor (filled by them for shipping) and pour back in the same amount of oil that the old compressor had. Simple enough, except the factory service manual says to add 0.7 ounces for the new receiver drier, 1.7 ounces for the new evaporator and 1.7 ounces for the new condenser. The new suction and high pressure line don't get anything added for them.

I plan to drain and measure the amount of oil in the old compressor and see how much is in there. Hopefully the numbers will work out pretty close when I add everything up.

 

That’s quite a big difference between your research and the FSM (7oz vs 4.1oz). I would follow the directions from the “instructions” pamphlet you get with the new compressor.

It is worth buying AC dye to add into your mineral oil. My first shot at refilling, I had a hole in the low pressure line, I was quick to notice due to the dye oozing out. Vacuum was good until I pressurized the system.

 

So far so good!
The last system to get working on my dads 1986 pickup restoration, the A/C.
After texts, emails and lots of phone calls I determined I could not find the correct kit.
The individual parts totaling almost $400, I had halted this project a few times.

I had the compressor out to find the numbers so I decided to clean up all the tubes and hoses.
The liquid line, installed by the dealer back in 1986, had a large rub hole.
Great news as this meant the compressor may still be good.

I drained the oil form every thing. I purchased a new dryer and expander for under $40.00.
I found an oil that is OK with mineral oil and PAG.
For $15 bucks I found a high pressure coupler, cut off the hole and reinstalled everything with new, green o-rings.

Free rental of gauges and a vacuum pump at the 'Green' auto parts store.
2 cans of R134a and 3oz of seal conditioner and I'm into this project for less than $100 bucks!!!

I did get the 7oz of oil into the system. U tube said to add more oil to make up for the decrease in gas, I did not.
I got 64% of R134a into the 27oz r12 system and stopped.

Like I said, so far so good.