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Mike S.
Mike S., ASE Certified Technician
Category: RV
Satisfied Customers: 7431
Experience:  GMC N.A.I.S.E. Certified Auto-Mechanic
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GMC forward step van: looking wiring diagram for

Customer Question

looking for engine wiring diagram for 1992 coronado fleetwood motorhome with 454 gm engine.
Submitted: 2 years ago.
Category: RV
Expert:  Mike S. replied 2 years ago.
Here it is.
Expert:  Mike S. replied 2 years ago.
With the engine off and key on run, check for voltage at both of those alternator connections.
Customer: replied 2 years ago.
the diagram is helpful and your comment is a small piece of the puzzle but not adequate to diagnose the issue. I am hoping that the diagram will help me diagnose the issue now that I have one. This is a motorhome on top of a 1992 gmc step van chassis. The wiring is a mix of things. I understand electric well and have been a designer for years. However without relavent diagrams it just takes longer.
Expert:  Mike S. replied 2 years ago.
Is there voltage to both wires?
Expert:  Mike S. replied 2 years ago.
If so, then the problem is the alternator. You can test if it's the voltage regulator or not by grounding the regulator against the frame through the "D" slot on the back of the alternator. That should max out the alternator and bypass the regulator, so you would need to hook up a voltmeter.
I used to rebuild alternators, so if it comes down to it, I can tell you how to take the alternator apart, test it and repair it.
Or you can just get a rebuilt/new one.
Customer: replied 2 years ago.
the diagram shows a 2 wire connection to the alternator alt fuse and red or battery power. then I expect a chassis gnd on the case. what does the pnk blc do is that the alternator field coil connection?
Expert:  Mike S. replied 2 years ago.
You didn't answer my question. Do both of those wires/connections have 12 volts with the key on run, engine off?
Customer: replied 2 years ago.
just answer the question, no I dont want to pay an additional 24 for a phone call. If the answers dont happen on this bb. then maybe I cancel the whole thing.
Expert:  Mike S. replied 2 years ago.
I didn't ask you to submit to a phone call, that is justanswer doing that.
I answered the question when I said "yes".
Now, if you want me to help you, you should answer my questions. Do both of those wires have voltage?
Customer: replied 2 years ago.
dont know that until I go tonight and try to connect to the alternator. I will also get a detailed pic of the alternator with my cell phone if possible. Maybe a model number and serial number might help. I understand from the drawing that there is supposed to be an inline fuse on the connector location F
Expert:  Mike S. replied 2 years ago.
I don't see a mention of an inline fuse. I see where the F terminal comes from the ALT fuse.
Customer: replied 2 years ago.
the text to the let of the wire says "ALT FUSE". I have ordered the GM service manual it should be here on wednesday. 65.00 plus shipping maybe it has some answers.
Expert:  Mike S. replied 2 years ago.
Yeah, "ALT" fuse as in alternator fuse.
Did you check for voltage to the wires yet?
Customer: replied 2 years ago.
Just removed air cleaner and took some pix to figure out what will be easiest method I now know what it looks like and tomorrow will figure out where wiring goes to fuse box under hood Outside coach. The alternator looks original Delco Remy
Expert:  Mike S. replied 2 years ago.
So I am assuming then that you did check for voltage and there is none to that field connection with the key on run/engine off?
Customer: replied 2 years ago.
I wont do the checks until I get the chassis wiring and maintenance manual tomorrow. Yesterday I took off the air cleaner, and got in and photgraphed the alternator. It has one attachment tab at 11 o'clock and the other at 4 o'clock. It also has a rigidity cross bar on top of it that has to be removed to replace the alternator. I have not found the alternator fuse yet. I need to trace the wire bundle back to the fuse block under the hood. when I get a chance later I will send you the pix of the engine and alternator. I am trying to identify it. It has stampings saying Delco Remy, but not model number
Expert:  Mike S. replied 2 years ago.
Why trace the wiring or do any of that without first checking if there is voltage at the alternator. If there is, then there is no need to trace any wire. If there is no voltage, then yes, find the ALT fuse and check it.