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A/C Conversion

I

Isaakfirestar

NAXJA Forum User
Location
Kansas
Hello everyone,
I recently added a new vehicle to my fleet, a 1992 Cherokee with the 4.0. It's in pretty good shape, but one of the major systems not working right now is the AC.
Since the system is on R12 and hasn't worked in years, it occurred to me that rather than rebuilding the R12 system with new parts and then converting, why don't I just put an entire R134a system in from a newer XJ, like the 1997 system with the parallel flow condenser.
However, I have a few reservations to doing this.
First off, if I replaced everything (compressor, condenser, evaporator, lines, dryer, expansion valve, etc.) would there be issues making it fit in my 92?
Right now I'm pretty set on using a parallel condenser, as the AC efficiency increase seems significant, and I plan to replace all parts regardless of which path I take.
Has anyone done a complete conversion like this before? I wasn't able to find any documentation of anyone who had.
Thanks all,
Isaak
 
I don't know what the differences are starting in '97, but both my '95 and my '96 came with 134a. I also have a '92 and it is my intention to convert it over to the same setup as the '95 & '96.
 
I think is '97 Jeep also switched to an orifice rather than an expansion valve. That changed the connection at the evap. Since that requires tearing the dash apart, I'm not surprised there's not much on it. The condenser is also plumbed differently.

As long as the evap lines are spaced the same and protrude enough to make the connection, you might be OK. Of course, swapping everything out can get expensive unless you raid a salvage yard.

FWIW, when I redid my '88 I went R12. Got my Sec 609 cert online which allowed me to buy R12. R12 is pretty pricey as well. My AC blows very cold.
 
That's what I'm trying to do. I want reliable AC so I intend to replace basically all of the parts I can. AC has never worked for me, and the previous owner never converted it so I need to do the whole R134a conversion myself. It just seemed like it might lead to a more reliable system to put a whole 97 assembly in.
 
Anak said:
I don't know what the differences are starting in '97, but both my '95 and my '96 came with 134a. I also have a '92 and it is my intention to convert it over to the same setup as the '95 & '96.
Click to expand...

Do your 95 and 96 both use the SD709 compressor or the SD7H15? My R12 system has the SD709, and from what I've read the SD7H15 is an improved version of the SD709... maybe the improvement was R134a compatiblity?
 
Saudade said:
I think is '97 Jeep also switched to an orifice rather than an expansion valve. That changed the connection at the evap. Since that requires tearing the dash apart, I'm not surprised there's not much on it. The condenser is also plumbed differently.

As long as the evap lines are spaced the same and protrude enough to make the connection, you might be OK. Of course, swapping everything out can get expensive unless you raid a salvage yard.

FWIW, when I redid my '88 I went R12. Got my Sec 609 cert online which allowed me to buy R12. R12 is pretty pricey as well. My AC blows very cold.
Click to expand...
So if I left the old evaporator and installed a whole 97 system underhood my new ac lines wouldn't be able to connect to the old evaporator? Is that due to the quick connect versus thread-in connectors?

R12 isn't an option for me, if I'm gonna replace everything I'm gonna do it right and put in the stuff I can buy at the store.
 
Anak said:
​

How can you tell?

I did a quick search and came up with this thread: https://www.naxja.org/forum/showthread.php?t=1112917

That thread ends with the same question.
Click to expand...

I believe the difference is that the SD709 uses the thread-on style connectors and the SD7H15 uses the block-type with a central nut. I also believe that the SD709 was originally meant for R12 applications and the SD7H15 was meant for R134a applications, but I don't know that for sure, hence my question.
Additionally, they should have a label on them calling out which style they are. Or at least mine does, front and center on the top of the compressor.
 
If you look at Sanden's website, you'll see the specs for each. The SD7H15 specs R-134a while the SD709 specs R-12 (there may be a few other differences). The SD7H15 basically replaced the the 709. I think originally it was due to both seal composition and oil pre-charge in them.

Nowadays, they're all made with same compatible seals. However, you should verify what oil it comes with before purchase. Not that it's a big deal. You're supposed to drain the compressor to measure how much oil is in it so you know how much to add to the system (if needed). While empty, you can flush the compressor to clean it out.

Just FYI, my Renix uses a Sanden SD508. When I bought it, it came with seals compatible with both R-12 and R-134a but was pre-charged with Mineral Oil. If the day comes that I need to swap to R-134a, I'll just flush the system, use an R-134a expansion valve and a new dryer.
 
I went and looked. "709T" is cast into the top of the compressor. I expect that means it is an SD709.

FWIW, it has thread-on connections at the rear, no block.

That is the '96. The engine bay of the '95 is buried under a pack rat's nest. I don't have the time to excavate that mess right now.
 
Saudade said:
If you look at Sanden's website, you'll see the specs for each. The SD7H15 specs R-134a while the SD709 specs R-12 (there may be a few other differences). The SD7H15 basically replaced the the 709. I think originally it was due to both seal composition and oil pre-charge in them.

Nowadays, they're all made with same compatible seals. However, you should verify what oil it comes with before purchase. Not that it's a big deal. You're supposed to drain the compressor to measure how much oil is in it so you know how much to add to the system (if needed). While empty, you can flush the compressor to clean it out.

Just FYI, my Renix uses a Sanden SD508. When I bought it, it came with seals compatible with both R-12 and R-134a but was pre-charged with Mineral Oil. If the day comes that I need to swap to R-134a, I'll just flush the system, use an R-134a expansion valve and a new dryer.
Click to expand...

That's what I had understood as well. They look like they would bolt-in to replace each other, although the AC hose connections are obviously different.
 
Anak said:
I went and looked. "709T" is cast into the top of the compressor. I expect that means it is an SD709.

FWIW, it has thread-on connections at the rear, no block.

That is the '96. The engine bay of the '95 is buried under a pack rat's nest. I don't have the time to excavate that mess right now.
Click to expand...

It sounds like the SD709 shouldn't have any issues playing nice with R134a then.

I'm thinking that rather than trying to retrofit a newer system on, I should get acceptable performance from replacing all the old parts in my current system with new ones. Maybe if this system fails again in the future I'll look into replacing it all with the SD7H15 system.
 
You may want to take a look at the differences between '92 and the '94-'96 parts. While the compressors may be essentially the same, they did make some changes to the hoses and the connections on the back of the compressor. It may be that those changes were for the sake of the new refrigerant. I am not an AC guy. I just see some different parts.

If you are going to buy new parts anyways, perhaps it would be best to get parts that were used with R134a rather than R12.
 
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