About to replace the entire AC system, a few questions first.

[351FUN]

Truck is a 92 Blazer, I have all the parts for the AC system including lines, condenser, evap core, etc. I've seen mention of setting the clutch gap, how do I do that? Factory style R4 compressor. I'm planning to replace everything and then take it to a shop to do the AC magic, should I leave anything unhooked or button it all up first? Is there anything I need to know or be aware of before I do that? I will probably leave the compressor unplugged when I take it in to make sure it doesn't engage at all. I've also read something about draining all the oil and then refilling it with the correct amount in case it's wrong, and something about half the oil going in the compressor and half in the dryer. Am I mixing up tips or is that the "3 oz. of OE-Specified Oil" called for on the compressor itself.

Thanks in advance for any tips and advice.

 

[PlayingWithTBI]

I've seen mention of setting the clutch gap, how do I do that? Factory style R4 compressor.

It's pretty easy if you have 2 sets of feeler gauges since the clutch wobbles when disengaged. You get 0.020" blades out on both gauges and slide them in between the clutch magnet and the front plate opposite from each other. If they slide in easily, keep adding blades until you can just slide them in. It s/b 0.020" - 0.030". If it's too big,l you have to tap the outer plate closer in. The nut usually runs out of threads when you try to adjust the gap with it. You're better off removing the nut and possibly add a washer to get your proper gap or just take a socket that fits over the stud and tap the plated in until it gives you the proper gap. I know it sounds hokey but it's a pressed on fit, the nut just keeps it from flying off. Some R4s don't even come with that nut.

I'm planning to replace everything and then take it to a shop to do the AC magic, should I leave anything unhooked or button it all up first?

After you flushed any reused parts, button it all up so you keep as much moisture out that you can.

I've also read something about draining all the oil and then refilling it with the correct amount in case it's wrong, and something about half the oil going in the compressor and half in the dryer. Am I mixing up tips or is that the "3 oz. of OE-Specified Oil" called for on the compressor itself.

I don't believe what they say, pour out the oil from the compressor and measure it. Then put ~4 oz back in it (rotate it a few turns to spread out the oil inside so it doesn't slug with initial startup), and another 4 oz in the accumulator/drier. I guessing you don't have a rear A/C unit in your Blazer.

HTH

 

[351FUN]

Nope, no rear air. I'm not planning to reuse any parts on it, I'm too scared of trashing a new compressor with something I missed. The only concern is the evap core depending on how bad the dash fights me.

 

[Greg Pace]

Nope, no rear air. I'm not planning to reuse any parts on it, I'm too scared of trashing a new compressor with something I missed. The only concern is the evap core depending on how bad the dash fights me.

I don't pull the dash, I cut the dash horizontal support with a Sawzall then take a Dremel with a 1/2" diameter saw and cut the plastic box and slide the evaporator out, takes 1/2 hour vs all day. You have to remove a coupe of screws, and silicone the piece back. You will be able to clean out all the leaves and crap and get much more air flow.

 

[Canadian Rust Bucket]

Pulling the dash is really easy, especially on the older models with fewer airbags. It took me around 2 hours, as a first timer, to pull the dash from my '95.
There's a really good guide on this forumhttps://www.gmt400.com/threads/dash-removal-and-replacement.38536/
Only thing I got mixed up was that you should pull the heater box out of the truck before you try to get to the evap core. I slightly broke the cover because I missed a screw. Unless your dash trim is incredibly brittle you shouldn't have much difficulty.

 

[1998_K1500_Sub]

You might want to follow this thread too…

Thread 'Sanden 4440 install'
https://www.gmt400.com/threads/sanden-4440-install.58192/

Good stuff in both threads.

 

[1998_K1500_Sub]

I've seen mention of setting the clutch gap, how do I do that?

There’s a tool (it’s probably rentable from AutoZone or O’Reilly) that is used to remove and replace (press-on actually) the clutch. Get one and give it a try.

 

[Schurkey]

should I leave anything unhooked or button it all up first?

Lube all your O-rings with Nylog Blue.
www.amazon.com/Refrigeration-Technologies-RT201B-Gasket-Sealant/dp/B008HOSQQQ/ref=sr_1_1?crid=3MB8UPO3R0Y8L

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Put everything together including whatever oil the system needs, the flourescent dye, then draw a vacuum on the system.

"I" would leave the vacuum overnight. Watch your gauge set, see where the needle is when you have run the vacuum pump for awhile. Tap the gauge, verify needle position. Close the valves on the gauge set, shut off the vacuum pump. Then come back the next morning, tap the gauge, see if the needle moved.

If it did not move, drive to the shop that's going to charge the system. You've just saved the shop the job of vacuuming the system, you've prevented the desiccant pack from absorbing moisture from the air in the system, and the shop doesn't have to vacuum and wait an hour or more before recharging.

When it was me...I charged it myself.

I will probably leave the compressor unplugged when I take it in to make sure it doesn't engage at all.

No point. The low-pressure switch will disconnect power to the compressor clutch.

 

[jrsroadhauze]

The R4 compressors don't hold up very well to 134A refrigerant. Replace it with a Sanden compressor.

 

[jdjonesdr]

I don't pull the dash, I cut the dash horizontal support with a Sawzall then take a Dremel with a 1/2" diameter saw and cut the plastic box and slide the evaporator out, takes 1/2 hour vs all day. You have to remove a coupe of screws, and silicone the piece back. You will be able to clean out all the leaves and crap and get much more air flow.

A man after my own heart. I have the complete system in new parts as well. Is that something you can take a picture of under the dash?

I've gone to a dozen different shops, and none can find the reason why my system discharges after 2 or 3 months. It's the most aggravating thing I have on my truck.