Plug and Play 1228062 swap to 1227747 A/C Issue

ECM as the title states...'88 S-10 4.3L 700r4 Holley TBI Comp Cam .428 .459 @ .050 200 206 ls 114 longtubes Ok...when I say we/us, that's because I have someone helping me with this venture. A little background...owner of said truck wants us to dial in the tune as it has cold start idle issues and seems to fall on it's face WOT. Since we have a zif modded 1227747 and felt we should leave his stock ECM unmolested, proceeded to swap the ECMs. The problem that we encountered is while everything seemed to work as far as trying to dial in the tune and how the engine responded to changes, we had lost A/C and wipers. Swapped 8062 back in and A/C and wipers are working again! Under further investigation looking at schematics, the S-T Auto bins have A/C clutch control on Pin A2. No problem, I'll just download a 1227747 S-T Auto.bin but they do not exist on this website as well as others!!! :mad1:

1) I've kicked around the idea of finish tuning with 747 and copy everything over to 8062 but I've somewhat had a reluctance as the spark map between the two are very different and further thoughts of copying everything line by line over scared me off when 747 has way more parameters disassembled not to mention Async vs Sync, too. I suppose log and burn w/ 8062 is another option.

2) I was also thinking as long as there's a A/C cycling switch in the system, we could de-pin A2 and permanently ground??? IDK if this would resolve the wiper issue.

3) Re-wire A/C system like the C/K R/V GP G/P M ST manual.

4) This is way over my head...add the A/C clutch control to the bin.:laugh:

5) Beg for 1227747 S-T Auto.bin
If someone has a solution to this problem, please chime in. :rockon:

Hello there.I swapped the 5.0l 7747 in place of 7429.a few wires didn't match.the ac was one.A2 on 7747 said not used.on tge 7429 the A2 and B8 both go to ac.not sure about which wire does what as my ac never worked so I left that wire out.as for the wipers I don't see what in the ecm harness goes to the wipers.I do have schematics for 7429 and 7747 to compare if it would help.the other thing different was egr related for evrv or egr solenoid. Also etm for hot fuel if I remember correctly had a difference also.I have my harness plug in view if a compare is needed.if i recall the ac going to B8 on 7747 is just for iac idle increase with ac on.if i can get into my garage i can check notes later today after work.nice ice storm here so I don't know if I'll get the door open .hth

The wipers may have been incidental but it did come back after the 8062 was put back in. Partner in crime was off island so haven't gotten back to the owner for round 2 of tuning. To be honest owner might tell us do what you gotta do but I like to leave things the way it came from the factory.

Thinking about it the 3 relays under hood.I don't have diagram right now but if I remember correctly one is f/p one is a/c one is wipers.all have ground supplied by ecm to activate the relays.I could be off on that but that would be a first check with 7747 in place. If u don't get ground to the relay at key on u get no power out of the relays.can verify once I'm home again.hth

Link to 1228062 Info: http://www.gearhead-efi.com/Fuel-Inj...Information-4E

Link to 1227747 Info: http://www.gearhead-efi.com/Fuel-Inj...Information-42 (4.3 Auto .bin files in post 4 and post 5)

dave w

Not sure why wipers aren't working because the 7747 and 8062 ECM's don't have anything to do with the wipers. (I could be incorrect)

The A/C clutch signal from the ECM goes to the relay for the A/C clutch, or at least that is how my ECM is wired.

Is no one else having this issue or is it because some/most people that do a V8 S10 swap originally w 8062, they ditch the A/C...there problem fixed!!!

I have an unmolested AKDX 747 that can try but as stated in post #1 S-T auto is what dictates which wiring scheme you'll have. AKDX does not meet that criteria. In fact unless I'm not seeing it, none of those bins listed fits "S-T auto."

There's not much on the internet about this dilemma but found this on TGO... https://www.thirdgen.org/forums/diy-...1228062-a.html

All other internet hits...all allude to upgrading to a PCM but if I'm understanding this correctly if you're replacing a 8062 S10 auto bin or even a 288 S10 auto bin for that matter you're going to run into this same issue. Suppose you could add the fan control to PCM and use that to cycle the relay for the compressor clutch.

Looking at the schematic it clearly shows an A/C cycling switch so I don't see any harm de-pinning A2 and permanently grounding it unless someone tells me otherwise.

Quote:

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Originally Posted by stew86MCSS396

Is no one else having this issue or is it because some/most people that do a V8 S10 swap originally w 8062, they ditch the A/C...there problem fixed!!!

I have an unmolested AKDX 747 that can try but as stated in post #1 S-T auto is what dictates which wiring scheme you'll have. AKDX does not meet that criteria. In fact unless I'm not seeing it, none of those bins listed fits "S-T auto."

There's not much on the internet about this dilemma but found this on TGO... https://www.thirdgen.org/forums/diy-...1228062-a.html

All other internet hits...all allude to upgrading to a PCM but if I'm understanding this correctly if you're replacing a 8062 S10 auto bin or even a 288 S10 auto bin for that matter you're going to run into this same issue. Suppose you could add the fan control to PCM and use that to cycle the relay for the compressor clutch.

Looking at the schematic it clearly shows an A/C cycling switch so I don't see any harm de-pinning A2 and permanently grounding it unless someone tells me otherwise.

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IIRC it is a normally closed relay, meaning the ECM grounds the relay to disable the A/C. The relay is more for WOT a/c shut-off than it is for anything else. It may also kick the compressor off if it enables and the engine idle rpm dips to low to prevent stalling.

From GM the 7747 never controlled the a/c clutch.