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Alternator upgrade/repair has me beat. Help!


MoonTimber

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So I've been trying to replace the alternator in my 1991 jamboree, which is a class c based on a Ford E350 chassis.

 

The new alternator is 110amps, where the old one was 75. The alternator shop installed a new rectifier in the alternator, which is a small plastic clip with two fat black wires with one small white wire coming out of it. They instructed me to cut the old rectifier out of the harness and crimp the new one in. This is where it got hairy.

 

The old one had two fat wires -black with an orange stripe, and one skinny red wire. I forgot to disconnect the battery before I stripped the ends and was reminded by bright sparks. I disconnected and continued.

 

I spent an hour and a half splicing the white wire to the red before working on the black pair. The black pair were buried deeper and I had to remove more of the flexible wire loom to get at them That's when the red wire popped out as if it hadn't been connected to anything with a teeny nub of copper showing.

 

I cut the loom another six inches to see if there was more red wire, but couldn't find any. I removed more parts and opened the loom 18 inches back. still no red wire.

 

Is it possible it was never hooked to anything, or did I fry a gigantic flushable link? I don't know if I'm stuck or already finished. I'm afraid to turn it on.

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Snag-20-Rectifier_1439.jpg

 

Let's try this photo of the old rectifier first. This was plugged into the original alternator. The three wires were covered in electrical tape and plastic sleeving as part of the engine wiring harness. I had to strip some of the plastic and electrical tape then cut them so I could expose enough wire to connect the new rectifier.

 

 

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Snag-20-Alternator_1438D.jpg

 

THEN I needed to open up the wiring harness a little more to work on the black/orange wires. But when I did the red wire popped out - as if it wasn't attached to anything. I cut the harness open 6 inches further down, then 18 inches further down, and I don't see a red wire or anything that the red wire might have been connected to. I only see the black/orange pair, and another pair of wires that I can trace to elsewhere in the engine compartment.

 

If the red wire was connected to a fusible link it's possible that it burned and evaporated when I had my accidental short and saw sparks, but I thought the fusable link would leave a residue behind and I don't see anything like that in the wiring harness. Is it possible the red wire was never connected to anything?

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I did an internet search and there are lots of drawings for an E350 alternator charge circuit. That might be a good start. I would have posted it here but I am not sure which one is for you.

 

I found a few drawings too, but I don't know if any of them are the right one, and I don't know what the designation is for the rectifier circuit. One of the diagrams shows one wire labeled BK/O connected to the alternator where it's labeled integral alternator regulator. But there is only one wire, where I have two of the black with orange. And I don't know if that's the designation for the rectifier, which is what the alternator shop called it.

 

I think I'm going to have to hire a mobile mechanic to finish my alternator installation tomorrow. This should have taken me 2 hours, but I've had my arms in that engine compartment almost seven hours now.

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I took a trip to the auto store and paid for a Haynes manual. Eventually I found a wiring schematic specific to my year and engine. I scanned it in the hopes that someone knows how to interpret these things. To me it looks like the red wire is an extra. I don't see a red wire exiting the alternator. If that's the case I don't need to hire the mobile mechanic. I just need to continue where I left off - crimping the B/O wires and bolting everything back in place.

 

Snag-20-Ford-E350-WiringA.jpg

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Call the alternator shop & explain what you explained here. I bet they can figure it out for you. Dave.

 

That was the first thing I wanted to do, except they are closed on the weekend so I crossed them off my list and forgot about them. I'll give them a call in the morning.

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If your motor home has two battery banks: one for starting the engine and the other for running the "hotel" functions (lights, etc) then it's possible that you have a diode isolator and that you need an alternator that needs a sense wire direct to the (usually start) battery. Is it possible that your "diode" is being used for this purpose?

 

WDR

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If your motor home has two battery banks: one for starting the engine and the other for running the "hotel" functions (lights, etc) then it's possible that you have a diode isolator and that you need an alternator that needs a sense wire direct to the (usually start) battery. Is it possible that your "diode" is being used for this purpose?

 

WDR

 

The E350 is designed with two batteries - one for the chassis and one for the coach, but I couldn't begin to respond to your question. I don't understand what a sense wire is or what a diode isolater would do.

 

One of the EE's on this forum told me that a rectifier is the circuitry that turns the AC produced by the alternator into DC. When I looked it up I discovered that the rectifier uses Diodes to make this happen, so I imagine that all of those diodes connected to my black/orange wire comprise the rectifier circuitry. Is that what you're referring to?

 

The sleeve with the Black/Orange wires also has a Yellow wire and a Yellow/Light Green wire in it, which makes sense based on the diagram above. I haven't run out to check, but based on the diagram I would expect to find the yellow wire connected to a water resistant relay, with a red wire coming out of it and feeding into the coach battery (which is on the opposite side of the engine). The sleeve that the rectifier wires fed into only has those four wires, and they all lead back towards the chassis battery. I haven't noticed the relay in the diagram though I will look tomorrow.

 

I called Fleetwood last week before buying my alternator. I wanted to find out if they had changed the wiring and if I needed to buy a specific alternator. They told me that when they build class C motorhomes, they don't modify the chassis. They order the chassis from Ford or GM or whoever, and when it arrives they leave the chassis alone and bolt the coach to it. Based on what they said I would imagine that the diagrams in my book should represent what's in the chassis. I'll take another look in the book and see if there is anything else that might shed some light on the alternator and rectifier.

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I could be wrong.. but that "should" be a pre H1 conversion rectifier/regulator connector to the light indicator/diode. In other words... you're good to go!

 

I would cut it just above the connector you pictured and tape it off.

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I didn't have a chance to call the alternator shop today, but I think you're right Yarome. The diagram doesn't show a third wire, so I'm going to take your word for it. I have to run some errands tonight but if I get home early enough I'll just finish bolting everything in and see if the engine starts up.

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My mechanic found another schematic on his AllData system. The third wire apparently goes to an optional rpm gauge which I don't have. I capped off that third wire and put everything back together. Engine started right up and purred away for a few minutes till I shut it off. The battery gauge on the dashboard shows it putting out a good level. WooHoo!

 

Start to finish the whole job took nine hours and should have taken two, but it's done and I can cross that off my list and move on to the next repair. Thanks everyone!

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