Where does this harness plug into?

[71CHEVYSHORTBED402]

Unfortunately most of the A/C system was removed from this truck with the engine rebuild (my bad, along time ago), so it makes things a little difficult to trace. I'll reinstall the A/C with the restore.

See that there three-prong plug harness marked "WTH?".........The plug was near the heater box when I found it. At any rate, where does that plug into? Two wires appear to run to the fuse box (I'm not there yet). It shares a green wire with the A/C switch. Note:This does not plug into the fan switch. That harness isn't shown.

Thank you for any input.

[SS Tim]

To me it looks like the anti-diseling relay connector.
12ga Orange
18ga Pink
14ga Dark Green

Refer to The 71 FSM 1A-41 fig.60 for a schematic and
1A-32 fig.41 for location and function description.

[med.bronze]

X2. ^^ I've only seen them on '71's

[71CHEVYSHORTBED402]

Originally Posted by SS Tim

To me it looks like the anti-diseling relay connector.
12ga Orange
18ga Pink
14ga Dark Green

Refer to The 71 FSM 1A-41 fig.60 for a schematic and
1A-32 fig.41 for location and function description.

Bingo, SS strikes again. Well, one guess who doesn't have the relay. From what I'm reading so far, it looks to mount on the panel near the ignition switch. I'm guessing above it. The unit may not be necessary (thoughts?). I'm not even convinced this ever had one. That said, dumb dumb (great mechanic turned meth-user) may have removed it when he installed the kill switch. Thanks a bunch Tim, and I learned something about reading the schematics. Now if you can cure some colored blindness.

Can anyone provide a description how and where the relay mounts? In the meantime, I'll do some looking.

Update: Just bought one. Safe bet mine was removed. Still doesn't mean I'll use it Ha!...............

[chewychevy67]

It mounts by the lighter under the dash

[71CHEVYSHORTBED402]

Thank you Chewy, doesn't get better than that.

Please advise if I'm mistaken, but it appears to use one tapered screw, though I may put a nut on the inside........and for lack of a better description, it doesn't require a ground wire to the body.

Thanks for the info.

[72 K20]

I put a new harness in my 72 and it has the anti diesel plug ,, the old one did not . does it have to be hooked up ? Or do I need to get a relay ? If there isn't an anti diesel solenoid on the carb what does the relay do ?

Thank you in advance ! Have a great day ! Tom

[SS Tim]

Originally Posted by 72 K20

I put a new harness in my 72 and it has the anti diesel plug ,, the old one did not . does it have to be hooked up ? Or do I need to get a relay ? If there isn't an anti diesel solenoid on the carb what does the relay do ?

Thank you in advance ! Have a great day ! Tom

If your "72" replacement harness had the plug it may have been a universal or simply a replacement for 71 and 72 with extra connectors covering both.

Your questions indicate you didn't read the manual referenced. So in a nutshell for 71 GM used the a/c compressor during shutdown to put additional load on the engine to prevent dieseling.

In 72 they used a dedicate idle stop solenoid as part of the TCS (transmission controlled spark) to alllow the throttle blades to close fully during engine shutdown choking the motor vs loading as an anti-dieseling control.

Most people have tossed the system and I see weekly "whats this relay/wire/stuff" posts on artifacts current owner's find.

To generalize most trucks had it and most people are using more advance allowing them to get by without it.

[71CHEVYSHORTBED402]

Been many years since I've seen an engine diesel. Do the classics have a propensity to diesel when the ignition is turned off while the air is on? I seem to recall that as a kid, but may be "going around to block to get next door".

Tim, are you suggesting I ditch the anti-dieseling relay for an alternative? More advance as in timing?

[VetteVet]

This is your harness and the dieseling relay is in the upper right corner.