R4 Scroll Compressor Experience

[SuperSpore]

I have since figured out the SD7H15 only works well on a single evaporator sytem, forget trying to use one on a dual system, just FYI.

Id be using this on a single cab. Any threads you can point to that would be helpful?
I was looking at one of those GDP scroll compressor kits on RA that replace the old pancake on an early 90's, but it seems people don't like the scroll type either.
(I don't know a lot about these compressors, so I'm unclear on the difference between the scroll and the sanden)

 

[L31MaxExpress]

Id be using this on a single cab. Any threads you can point to that would be helpful?
I was looking at one of those GDP scroll compressor kits on RA that replace the old pancake on an early 90's, but it seems people don't like the scroll type either.
(I don't know a lot about these compressors, so I'm unclear on the difference between the scroll and the sanden)

The scroll is not very efficient at idle rpm. You will be good to go with the Sanden on a single cab IMO. I put the same 4261 Sanden SD7H15 that was on the dual evaporator system in my 1997 on the 1987 G20 with front dash air only. It cools great in that system. So good in fact that I found out the old factory cycling switch is failing. I attempted to adjust it and the slightest movement now either causes the compressor to not run at all or run all the time, freezing up the evaporator core. I have a replacement switch on the way. Those older switches typically last forever so I thought I would leave it since it was working when the van was last parked.

 

[1998_K1500_Sub]

I was looking at one of those GDP scroll compressor kits on RA that replace the old pancake on an early 90's, but it seems people don't like the scroll type either.
(I don't know a lot about these compressors, so I'm unclear on the difference between the scroll and the sanden)

OP of this thread seemed to think the scroll was OK, but I don't deny @L31MaxExpress' comment that they're inefficient at low speed... which may or may not matter to you.

You might search for "scroll" on GMT400, I swear I've seen at least one other thread with some discussion on that type.

Heat soak was mentioned earlier in this thread. GM addressed this on the S10 trucks (at least in 1995, possibly on earlier S10 R4 deployments as well) with an AC clutch turn-on delay; the clutch would only engage after the engine had been running for... 20s maybe. When I was young and dumb I found this a huge inconvenience; now that I'm old and dumb I finally understand why GM did it. AFAIK, this delay wasn't deployed on the GMT400s, but I could be wrong.


(additional comments follow)

For those that may not understand (I didn't at one time), Heat Soak is when the underhood temps climb after engine shut-down, which causes the AC high-side pressure to increase greatly in accord. This pressure rise isn't a major consequence until the engine starts and the AC compressor immediately engaged; then, the high-side pressures briefly go through the roof and, if there's no high-side cut-out switch to disengage the compressor, the atypically high pressures cause seals to be breached or other nasty consequences.

So to mitigate the effects of heat soak it helps to delay the compressor turn-on for a short while after engine turn-on. This gives the engine fan time to pull air through the AC condenser, reducing the refrigerant temp and thus the refrigerant high-side pressure, prior to engaging the compressor This helps avoid nasty consequences.

For this reason I try to disengage the AC on engine shutdown so that it doesn't immediately engage on start-up.

$0.02

 

[L31MaxExpress]

OP of this thread seemed to think the scroll was OK, but I don't deny @L31MaxExpress' comment that they're inefficient at low speed... which may or may not matter to you.

You might search for "scroll" on GMT400, I swear I've seen at least one other thread with some discussion on that type.

Heat soak was mentioned earlier in this thread. GM addressed this on the S10 trucks (at least in 1995, possibly on earlier S10 R4 deployments as well) with an AC clutch turn-on delay; the clutch would only engage after the engine had been running for... 20s maybe. When I was young and dumb I found this a huge inconvenience; now that I'm old and dumb I finally understand why GM did it. AFAIK, this delay wasn't deployed on the GMT400s, but I could be wrong.

I think my 87 S15 Jimmy had a turn on delay too, never bothered me much though. It is hot enough here, typically roll down the windows and blow the hot air out for a minute or two of driving, run the system on non recirculated air, then roll the windows up to where they are still cracked open a bit for another mile or so before finally rolling them up all the way and switching to recirculate. Good practice to blow that heat out from the start as it is a bit detrimental to long compressor life to force the AC system to try to cool 150F air. Using outside air from the start it actually cools down more quickly than pulling hotter interior air. Once the interior is cooler than outside air, switching to recirculate brings the interior temps down more quickly. In over 20 years of driving, have found this the most effective way to cool down a hot interior the quickest.

 

[studigggs]

Just to update this thread since it got rehashed, that GPD scroll in R4 form factor I installed in 2019 is still going strong.

 

[SuperSpore]

Just to update this thread since it got rehashed, that GPD scroll in R4 form factor I installed in 2019 is still going strong.

Thanks for the update...
Is something like this what you installed? https://www.rockauto.com/en/moreinfo.php?pk=12710637&cc=1031184&pt=17507&jsn=981
That compressor in the link looks very different from the R4 pancake that comes with the early 90's.
If what you installed looks like the pic in the link I'm wondering if it's a direct bolt on to the OEM bracket?

Edit: I just realized you're the OP of this thread... and after seeing the video you linked, it sure looks like a pancake compressor. lol
I guess rock auto went with a generic picture of a random compressor in that link? If you have any other info that would be helpful let me know.

I see that PlayingwithTBI gave a suggestion on wiring the high pressure switch. I don't have a max air/recirculate button... but
I'm gonna see if I can find a good post on rewiring that.

 

[dave s]

I used this scroll type back on 5/9/21 andit's still going strong. That said, I do not drive it much. But I used it around the farm this last week multiple times and it was sitting idling while I loaded brush and it was freezing me out. Granted it was only in the 80's but worked well for me. Here is a copy of my order for my 94 regular cab.

GPD 9611687A (New - With A/C Condenser) Includes A/C Condenser; w/ Upgraded Design Compressor; Compressor Prefilled w/ OE-Specified Oil Info
6 Groove; Scroll Replacement For 7511351 R4

 

[Tomcat71]

I think my 87 S15 Jimmy had a turn on delay too, never bothered me much though. It is hot enough here, typically roll down the windows and blow the hot air out for a minute or two of driving, run the system on non recirculated air, then roll the windows up to where they are still cracked open a bit for another mile or so before finally rolling them up all the way and switching to recirculate. Good practice to blow that heat out from the start as it is a bit detrimental to long compressor life to force the AC system to try to cool 150F air. Using outside air from the start it actually cools down more quickly than pulling hotter interior air. Once the interior is cooler than outside air, switching to recirculate brings the interior temps down more quickly. In over 20 years of driving, have found this the most effective way to cool down a hot interior the quickest.

that is what I was taught years ago. Get in roll the windows down and drive for a min or two and let the cabin air out instead of trying to make the AC system remove all that heat right at the start.

 

[PlayingWithTBI]

I see that PlayingwithTBI gave a suggestion on wiring the high pressure switch. I don't have a max air/recirculate button... but
I'm gonna see if I can find a good post on rewiring that.

Here's what I did with mine, including a relay that givers the compressor full battery voltage. The mods are in blue. This works great, I haven't had any explosions since, LOL

You must be registered for see images attach

 

[PlayingWithTBI]

I'm gonna see if I can find a good post on rewiring that.

Here's the thread I started with replacing the clutch and went on to rewiring the clutch on page 2
www.gmt400.com/threads/swapping-the-clutch-on-an-r4-a-c-compressor.49928/

Swapping the Clutch on an R4 A/C Compressor

The other day when I was waiting for curb side delivery at Total Wine my A/C started blowing warmer to the point it was cooler than the vent but not cool enough to keep me from sweating. It got a little cooler when driving home on the freeway then, when I got off at my exit it started blowing...

www.gmt400.com