Automatic Shut-Down Relay? A/C Clutch cut-out relay?

[Begle1]

How are the automatic shut-down and A/C clutch cut-out relays wired?

I assume that the A/C cut-out relay is a normally closed relay that opens and cuts power to the clutch when the ECM gives it power?


I have no idea what the automatic shut-down relay even controls...

Anybody got schematics? The popular online-scanned 91.5 schematics (thanks Den) don't seem to have the shut-down relay in it, so is it something they added later?

[Begle1]

Help me please? It's for a girl.

[Begle1]

There is such a thing as an A/C clutch cut-out relay and an automatic shut-down relay, correct?

[Tintacker]

You need a shop manual for a '90. My '92 shop manual says the ASD relay controls the voltage to the alternator field winding, and the ground for the relay is switched on and off via the ECM.
Same thing with the A/C relay, ground circuit is switched by the ECM to cycle the compressor.

[Begle1]

This isn't for my truck, this is for a '93. My truck never had either relay.

http://www.dieselbombers.com/1st-genera ... relay.html



So the ASD relay control coil has a constant +12 and an ECM-switched ground, and it controls +12 voltage to the alternator. Does the +12v it get come from the ignition switch or straight from the battery? Are the contacts wired normally closed or normally open?


The A/C cut-out relay control coil has a constant +12 and an ECM-switched ground and it controls +12 voltage to the A/C clutch. Where does that +12 come from? ECM or switch on the HVAC panel? Are the contacts wired normally closed or normally open?

The 91.5 manual schematics don't seem to have either relay.

[Tintacker]

Ok, both the ASD and A/C relays are switched the same with the positive from the ignition switch (same circuit as the VE fuel solenoid) and the neg switched from the ECM. Yes, the relays are normally open.
The A/C relay does have it's own fuse link for it's hot side but I don't think that's her problem. Reading that thread I can't figure out what her "alternator guru" did to wire up the external regulator.
That's the mystery here and I think that is the source of her headache. The ECM needs to see voltage from the ASD relay. The crazy clicking from the relay is probably the ecm trying to control the field voltage to the alternator or his splice job fried the ECM and it's just going nuts (just a guess at this point, sorry). If she wants to keep the external reg she will have to live with that ecm trouble code and most likely a check engine light.
If it were my truck, I would get the "guru" to undo everything he did, check all the wires then check/replace the crank sensor. If that does not fix it, replace the ECM.

I'm not an expert, just my $.02

PM me your # if you want to get more in depth. My fingers hurt.