If I’m doing a complete replacement on an obs truck I always go in with 94 parts for use with r134. Bigger condenser, more adjustment with the pressure switches overall much better performance.
AC question?
- Thread starter larson
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ComatoseLlama
Full Access Member
Thanks for the info! Trying to add a/c to my truck and there’s not much in the way of guidance out there. I’m gonna try and do a tech article when I get around to it.
Edit: if anyone has an A/C bracket for the 7.3 please let me know id love to throw some stimulus your way!
Edit: if anyone has an A/C bracket for the 7.3 please let me know id love to throw some stimulus your way!
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Macrobb
Full Access Member
BTW, when JY hunting for the OBS trucks - the compressor that "looks" like ours has two variations. One ends in 10 and the other in 15. The 10 is garbage and won't hold up to R134A very long; the 15 is better.
If you are using something other(R290, freeze 12 etc), you may be able to get away with the cheaper one... but the key on both of these compressors is lubrication. You want a very light-weight oil for these - PAG oil for R134A, ATF for "other" refrigerants.(Don't ask how I know this<_<).
Also, if you blew a high side seal, your pressures may be getting high because the orifice tube got blocked. Pull and check it.
I'd also grab the high pressure switch from a more modern car and wire it "inline" with one of the compressor solenoid wires. The sensor literally just screws on the schraeder valve on the high side, and isn't hard to wire in.
If you are using something other(R290, freeze 12 etc), you may be able to get away with the cheaper one... but the key on both of these compressors is lubrication. You want a very light-weight oil for these - PAG oil for R134A, ATF for "other" refrigerants.(Don't ask how I know this<_<).
Also, if you blew a high side seal, your pressures may be getting high because the orifice tube got blocked. Pull and check it.
I'd also grab the high pressure switch from a more modern car and wire it "inline" with one of the compressor solenoid wires. The sensor literally just screws on the schraeder valve on the high side, and isn't hard to wire in.
YJMike92
Full Access Member
I hope you didn't mean to say ATF?
Macrobb
Full Access Member
Yes. I totally did. Automatic Transmission Fluid. Dex/Mercon.
It's a high-temp, light-weight oil, often synthetic. Works well with aluminum. What's not to like?
I killed a couple of those stupid(used) compressors with "compressor mineral oil". It was just too thick, would work itself out of the pump and not circulate.
Tried ATF as a last resort... and no more issues.
(I've also used ATF for all sorts of other stuff - generic lube for siding parts, lubing up oilite bushings in worn fans... anywhere 3 in 1 oil would be used, I now use ATF. And have much better results).
Thank you for this. I've been wondering how to best go about this myself.
YJMike92
Full Access Member
If it works for you, go for it. I've never had a problem using the recommended refrigerant oils. ATF in the other applications mentioned sounds good.
A slight tweak of the low pressure switch will usually make it work better with r134a conversion also.
I posted about some parts from Four Seasons that were of questionable quality after I replaced EVERYTHING, must have been on another thread.
This was one of the parts that gave me a headache. Four Seasons listed a low pressure switch that specifically said for r134a conversions. Imagine my dismay a month later when I found out that all my refrigerant had leaked out of the low pressure switch, as evidenced by the oil all over the switch.
Booyah45828
Full Access Member
Yes, if you want it to last.
Anytime we install a compressor, the warranty for the reman requires proof of the replacement of the orifice tube/expansion valve and the accumulator/drier.
If your truck was originally a 92 and was came with r12, either use r12 as the fill, or one of the r12 substitutes.
If you use r134a, go through and replace all the seals and o-rings in the system. Every conversion that I didn't do that on always leaked. And make sure the new compressor seals are compatible with r134a.
You can play with different sized orifice tubes. I've had luck with the performance from installing variable orifice tubes. Google it if you don't know what they are.
Flushing any system is always a good thing, as is removing and inspecting the orifice tube. Even if you don't think it's dirty, you might be surprised.
As far as brands are concerned, the last time I talked to our parts rep, he said most of the reman compressors are rebuilt by the same place, so quality should be the same for all. The overseas ones are hit or miss, but that's with most overseas parts.
david85
Full Access Member
I used PAG oil with HC12 refrigerant. May not be legal in all places by way cheaper and easier to use (no license required either).
The problem with HC-12a is it's flammable. I think it is legal to use in other countries though.
My buddy who does my state inspections in PA, his father used to run a garage, they would occasionally work on AC and there was a "lazy way" his dad would work on his own ac stuff that was R12 originally but needed to be 134a. First jump the low pressure switch and see if the compressor will spin at all, second jam a can in and see if you can get any pressure to read without blatantly leaking out as fast as it's going in to make sure you don't have a legit rust hole. If that works, add ester oil into the system before filling any further to swell the seals up some and put in enough cans to get the ac to operate even if it isn't perfectly efficient. Run it this way for at least an hour so the oil can circulate and get absorbed some near any dry seals. After this, purge the system (I'm not advocating this part or any of it really), the moisture will come out of most of the system if there was any with whatever else was in there. Then add pag oil, only half the amount the system calls for and fill the system with 134a until the compressor stops cycling with the R12 pressure switch, no more than 8 oz after the system stops cycling.
I will admit that though this isn't the "right" way to do this, when I got my first IDI and hadn't learned to do things right yet, I tried this only from knowing about it from a story he had told me about his dad half assing stuff sometimes... and it's the coldest AC I have. Colder than 2 systems I replaced everything and did totally correct. I'm not saying it's because this method is better, but I think something can be said for some of the older ac parts on our truck being more stout and compatible with 134 than we give them credit for sometimes. I think a new clean orifice valve, and a clean system with good working pressure switches is the most important part.
I will admit that though this isn't the "right" way to do this, when I got my first IDI and hadn't learned to do things right yet, I tried this only from knowing about it from a story he had told me about his dad half assing stuff sometimes... and it's the coldest AC I have. Colder than 2 systems I replaced everything and did totally correct. I'm not saying it's because this method is better, but I think something can be said for some of the older ac parts on our truck being more stout and compatible with 134 than we give them credit for sometimes. I think a new clean orifice valve, and a clean system with good working pressure switches is the most important part.
