I just added A/C to my 1955 chevy pickup. I forgot no fan in 1990. Need pinout for A/C clutch to ECM. Have low idle problem. This a R/V1500. Not CK1500 Same ECM but uses different pinouts than CK1500. There are different wiring diagrams. While moving lost warring diagram.
Last edited by fflen9899; 07-28-2015 at 05:23 AM.
The 7747 doesn't have fan control. It does get an AC input on B8, but I believe that mainly just adds IAC steps. I haven't seen a need to have any AC input when using a 7747 on any of my builds.
1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
1975 280Z, TBI 350, 700R4
1953 M-38A1, TBI Buick 231
1951 Ford Panel, 5.3 with 4L80E
The A/C is aftermarket. I forgot that year truck didn't have a electric fan. I need a signal to increase the idle when the A/C is on. IAC? The compressor lowers the RPM's and stalls the engine. Stock it had to have some signal to raise the RPM's Is there a pinout that I could connect to that tells the IAC the A/C is on, and raise the idle? I could use a after market switch but would like to use the ECM. The system minus the A/C came off a 1989 R1500 suburban and is now on a 1955 chevy pickup. For the fan problem maybe I could use the clutch connected to a relay to turn the fan on.
So the clutch tells the ECM that it's on, than the ECM tells the IAC to step up until it reaches a normal idle? Like drive to park. The wirring diagrams R/V1500 and CK1500 look to have different pinouts. I know GM changed the CK family first than about two years later the suburbans. I'm looking at a 1988 - 1990 and it doesn't show a B8 is being used. This is new to me any help would be appreciated.
Last edited by fflen9899; 07-28-2015 at 05:10 AM.
Sorry new to posting in forums to. Need wiring for A/C clutch to ECM pinout B8 doesn't seem to be used on the R/V1500 wiring diagram. Is it the green wire? Don't have the truck here to look is't in transit. Just trying to figure this out before it arrives. Tucson AZ 112. I think I'll need the A?C to work. Thanks
I thought there was a patch to control an e-fan with the '7747, but think I'm confusing it with the '7427... Have you looked at EBL Flash to upgrade your '747? dynamicefi.com I don't believe you wire the clutch directly to B8. You will need to use the a pressure switch and a relay. Check out this diagram: http://dynamicefi.com/EBL_Drawings_Images/4of4.jpg
I'am very new at this, I mean very new. Right now I'am just trying to make things function. All I've ever done was install a TPI system and now this 1989 R/V1500 stock EFI to a very low HP small block chevy crate motor. I used the stock wiring harness and modified as I went. I started out with a CK1500 wiring diagram quickly found out that the CK1500 was upgraded about two years before the R/V1500 even the body style. Can't remember what year. Can anyone tell me if I'am right. To my knowledge they are not. Different ECM? or just programmed different. Hard to find wiring diagram R/V1500 with pinout functions. I can work around the fan but the idle I'am not sure. It has to be like lowering the idle in park raising in drive. ECM to IAC? I just don't know how the ECM thinks or the pinout functions.
thanks
The wiring from '87-'92 is basically the same (except for '7060 brown connector ECMs), just physically routed differently depending on body style. B8 is where the '7747 needs to see 12 volts in order to raise the idle (IAC counts) when the AC clutch is engaged.
1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
1975 280Z, TBI 350, 700R4
1953 M-38A1, TBI Buick 231
1951 Ford Panel, 5.3 with 4L80E
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