AC repair/overview on a 30 year old truck

[studigggs]

My advice would be to replace everything except the evap behind the dash. Get new pressure sensors w/ propper R134 calibrations, condenser, compressor, dryer, o-tube, lines and o-rings. Splurge and buy the AC-Delco o-rings for the back of the compressor. RockAuto has a great breakdown and choices for everything you need. You could even get everything purchased and installed DIY, but leave the evap open. take it to a shop and ask for an evap flush, evac/leak test and charge on the system. This way you dont have to buy any HVAC tools and you save the labor for part swapping.

 

[wb292]

Last year I replaced the entire system using as many AC Delco parts as I could from Rock Auto. I spent maybe $500 total. The worst part of the job was the evap core. You don't have to remove the whole dash. Just loosed the bolts and screws enough to pull it back about a inch. Took me two weekends and it works great in the AZ summer.

 

[Caman96]

My advice would be to replace everything except the evap behind the dash. Get new pressure sensors w/ propper R134 calibrations, condenser, compressor, dryer, o-tube, lines and o-rings. Splurge and buy the AC-Delco o-rings for the back of the compressor. RockAuto has a great breakdown and choices for everything you need. You could even get everything purchased and installed DIY, but leave the evap open. take it to a shop and ask for an evap flush, evac/leak test and charge on the system. This way you dont have to buy any HVAC tools and you save the labor for part swapping.

^^^This was same advice I posted earlier and exactly what I did. OP then says he didn’t know what parts to order. I tried on RockAuto, but when looking at AC hoses they have different applications and I don’t know how they apply to his.

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^^^Both listed for 92 Chevrolet Blazer

 

[1998_K1500_Sub]

^^^This was same advice I posted earlier and exactly what I did. OP then says he didn’t know what parts to order. I tried on RockAuto, but when looking at AC hoses they have different applications and I don’t know how they apply to his.

You must be registered for see images attach

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^^^Both listed for 92 Chevrolet Blazer

Yeah, RockAuto does this kind of thing (mis-listing).

@351FUN, I too emphasize what others said earlier in this post; replace everything you can. AC systems work best and longest when their internals are *clean*. Replacing everything (and doing it carefully to mitigate any dust during assembly) is the way to go, if finances and ability allow.

There's one other funky thing to note: An R12 system may LOOK the same as an R134a (hoses and fittings, etc.) on different year trucks, but their parts aren't necessarily interchangeable... I've seen cases where the thread pitch on the fittings was different, even though the fittings looked like they should mate (specifically, a R134a receiver drier for a 1995 S10 and the corresponding hose assembly from an earlier R12 S10... fittings sure LOOKED like they would / should mate, but thread pitch was different). So, don't try to mix-and-match across different year's AC parts... or, if you do, be prepared for a possible disappointment.

If OP plans to replace the ENTIRE system, he might consider using replacement parts from an R134 truck (e.g., 1995). Otherwise, if possible I suggest using parts for his model year.

 

[1998_K1500_Sub]

Keep in mind, when converting from R12 to R134A you need to completely flush the system. The Mineral oil used in R12 is not compatible with PAG oil used in the R134A system. You can use an Ester oil but, I prefer to flush the system - it needs to be flushed anyway.

I'm not keen on using Ester, I've seen compressor mfgrs say NO to that (see attached), not as the primary oil fill anyway.

@351FUN: Use an appropriate viscosity PAG oil. If you're really particular, find and use double-end-capped PAG (see attached).

 

[1998_K1500_Sub]

And if you do get a compressor do the research and make sure it has the correct type and amount of oil in it before you install it.

OP might trust but verify that the compressor has the right amount.

Better process:

- drain all oil out, measure, confirm volume (allowing for oil remaining in compressor)
- confirm the amount of oil req'd for system (I think it's 8oz)
- discard any excess, if present
- add half of oil to the new receiver / drier and install
- put remaining oil back in compressor

Variant of the above: I always toss any oil I've drained and use new oil of known type and viscosity (e.g., from a container that says PAG46, etc.)


Side node: I think the ACDelco R4 compressors have NO oil in them; that was my experience anyway. Then one can use whatever oil volume / type / viscosity is appropriate.

 

[PlayingWithTBI]

On another note, measure the clutch air gap, s/b 0.020" - 0.030". I had a new NAPA R4 compressor with over 0.080" which I discovered after it smoked it in about a week.

Edit: The nut holding the clutch on the shaft doesn't adjust the air gap, it's just there to keep it from flying off. You can add a washer and use it to adjust or, just press the clutch on until you achieve the proper gap.

 

[351FUN]

I didn’t say 4 doors. When I enter information for a 1992 Blazer on RockAuto and look at A.C. Hoses, it shows hoses for With or Without Rear Air.

Like I said, rear air is only on 4 door vehicles. Blazers are only 2 door vehicles. Rear air does not come in blazers.

My advice would be to replace everything except the evap behind the dash. Get new pressure sensors w/ propper R134 calibrations, condenser, compressor, dryer, o-tube, lines and o-rings. Splurge and buy the AC-Delco o-rings for the back of the compressor. RockAuto has a great breakdown and choices for everything you need. You could even get everything purchased and installed DIY, but leave the evap open. take it to a shop and ask for an evap flush, evac/leak test and charge on the system. This way you dont have to buy any HVAC tools and you save the labor for part swapping.

I'm planning to replace as much as possible, this thread has taught me a ton.

On another note, measure the clutch air gap, s/b 0.020" - 0.030". I had a new NAPA R4 compressor with over 0.080" which I discovered after it smoked it in about a week.

Edit: The nut holding the clutch on the shaft doesn't adjust the air gap, it's just there to keep it from flying off. You can add a washer and use it to adjust or, just press the clutch on until you achieve the proper gap.

Case in point, I'd never heard of doing this but I'll make sure it's set right.

 

[Caman96]

Like I said, rear air is only on 4 door vehicles. Blazers are only 2 door vehicles. Rear air does not come in blazers.

Like I said, that info was directly from RockAuto site, and I was only there looking to help you because you said:

I don't even know all the parts I need to change

 

[1998_K1500_Sub]

@351FUN, others here have suggested you replace all the hoses and o-rings, which is a good idea.

It's actually more than a good idea, it's a requirement AFAIK.

What hasn't yet been said is that the hoses and o-rings used in R12 systems weren't designed for R134. Their permeability is higher (too high?) when used with R134 and they'll provide a leakage path for the refrigerant.

So, commit to disassembling the entire system, replacing all the hoses, getting new o-rings, and re-assembling.

This would apply to any R12 system.

Note: You could, if you wished, take your existing hose assemblies to a competent AC shop and have them replace the hoses with low-permeability hose (and retain the existing hard line and fittings). This makes most sense on an older vehicle where new replacement assemblies aren't available. Price-wise, I'm not sure which approach would be better for you, "buy new" or rebuild.