1986 E350 chassis 460 gas engine

[raccoonman]

Looking for what I may have damaged when I accidentally hooked up the chassis battery backwards. It was not hooked up to the isolator at the time, fortunately. When battery is correctly hooked up, I can jump the starter relay and get the 460 to turn over. No lights from/through the light switch; no function from the ignition switch. I'm told (and should know these things, but) the power all runs through the alternator and, if hooked up backwards, the alternator diode trio fries, rendering the normal circuits dead until a good alternator is installed. I am not an electronics tech by any stretch of the imagination. I need the simplest work through to identify the faulty parts and replace them. Thanks! BTW there was no coach battery installed, either, nor is there a generator installed.

[DAN33]

Check for a blown fuse link at battery side of starter relay.This is where power is fed to buss bar.

[subford]

Sounds like open fuse links at the starter relay.
Check all of the fuse links by trying to streach them apart. If they streach they are bad.
After replacing the bad one see if it will crank with the key.
If it cranks and does not start you might have to replace the Ignition Control Module.

[subford]

Originally Posted by DAN33

This is where power is fed to buss bar.

Buss Bar???

[raccoonman]

Other than some crappy connections, which I redid, there's no obvious burned fusible links. I'll have to strip the looming off all the wires coming from the starter relay out to see if anything's burned through. I did find a relay on the opposite side of the engine bay in that same circuit which could be bad. I think I'll also drop the alternator tonight and take it and have it tested tomorrow. Going to replace the positive battery cable as well, because it's just too short and difficult to mount to the battery. Not to mention just a little bit fried.

[subford]

The relay on the opposite side of the engine bay is the charge relay for the coach battery.

[raccoonman]

I wasn't clear enough, I knew what that one was because it's got heavy gauge cable to it and running back along the chassis. This one is up tucked under the radiator support, small black box. couldn't read any markings on it last night. Funny thing about all this is the absolute lack of a "burnt wire" odor in the cab or under the hood. Got to be something absolutely ridiculously simple in the end, just gotta find it. Bemused also by the lack of paint on the engine, not a bit of paint whatsoever. I'm used to blue and then grey, but bare metal is out of the ordinary to me. My Pace Arrow's 454 was Chevy Orange top to bottom.

[subford]

You might be speaking of either the voltage regulator for the alternator or the Ignition Control Module (ICM).
Do you have any photos?
The ICM:


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[raccoonman]

Nope, found the ignition relay online. The DSII box is -visually- okay as they often have a tell-tale trail of melted potting compound if they fry. I've been told by a tech here at work to check for bad wire at the ignition switch itself. Here's to another evening checking wiring! Can't identify the alternator from online pics; going to have to pull it and have it checked.

[raccoonman]

Ye Gods and Monsters.... Whoever designed the dual AIR pump/alternator bracket ought to be whipped. Getting the alternator out was definitely a chore. Going to swing by one or two of the chain stores and have it checked today. Job whipped my old butt so bad I didn't do much more last night. Also, that bracket was loose and rattling before I ever touched it with a wrench.... wonder if the DPO was troubled by rattling from the front of the engine? Also, the wiring to the two plugs was in good condition, so I'm feeling confident the alternator is okay, even if it's not, it's not too expensive to replace.

[subford]

Not sure what you are calling an Ignition Relay as you should have no such item.

Here is a photo of the wiring at the Ignition Switch.


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[raccoonman]

That's my next target; it's not terribly difficult to reach. Any scorched wires there should be obvious. Amazingly the alternator is marked for only 60amps. I would have thought they'd have gone for 78 to 100.

[raccoonman]

Nothing burned at the ignition switch; removed all the loom wrap from the wiring harness from the starter relay to the driver's side firewall, found nothing obvious. jumped four fusible link wires that are topside, nothing. Haven't checked the wire that should piggyback to the starter. Haven't pulled the headlight switch, either. Jumped the ignition wire to positive and jumped the relay, engine turned over but would not start. No action on the instrument panel when ignition terminal jumped, where the gauges should have reacted. Returned everything to stage one except fusible links. It's going to be just one thing causing all of this confusion; that's always been my experience. Still amazed that the alternator is only rated at 60A..... then again, my Falcons all used 35A alternators or generators

[subford]

Maybe these wiring diagrams may help.




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