Alternator woes

[partsflyin]

I have a 1981 E-350 Quigley. Its an ex-ambulance. I recently had the alternator go bad on me.
When I pulled the alternator I found it to be an extra heavy duty 165 amp unit, i am assuming this was required for all the interior extras of the ambulance. I sent it to a local shop to see if it could be repaired , with no luck. I was quoted $450 or so for a direct replacement:Wow1:.
I did some digging and found a 100 amp single wire Delco alternator for $114 , that looked like with a little tweaking I could make work with the original brackets.So i jumped on it.
The original alternator had a + stud and a - stud on the back.
Last night right at dark i got the new Delco alternator installed and fired up the van. Not charging! (per the new voltmeter I also installed at the same time , just under 12 volts)
At that time I remembered I had forgotten to do anything with the negative cable from the original alternator.
Is this why my system is not charging? Can I ground this cable to the engine block to correct my my problem?
Thanks for your help!

 

[eugene]

There are a couple different styles of delco alternators, some may need the sense wire connected from the battery before they will start charging. Even though it is single wire, IIRC that refers to a single charge wire, I beleive there is still a smaller plug with the sense wire. On my work laptop at the moment so I don't have the info handy. Look at some of the wek sites with they DIY generators where people hook them up to lawn mowers and such, one of those has references for the various different models.

 

[wrcsixeight]

Follow the alternator's hot cable to the battery. There might be a fusible link along the way that has blown. I don't know if Ford Used fusible links but they were common in cars till the early 90's.

What is a Fusible Link?
A fusible link is a short piece of insulated low-voltage cable within an automotive wiring harness that is designed to protect the harness in applications where a fuse is unsuitable. In an extreme current overload situation, the conductor within the link is melted while the ensuing flame and spark is contained within the link's insulation.

They are supposed to stretch out and look burnt when they fail. The one on my alternator cable did neither.

http://www.whiteproducts.com/fusible-faqs.shtml

I have grounded my alternator's negative post to the frame and engine.

 

[partsflyin]

There are a couple different styles of delco alternators, some may need the sense wire connected from the battery before they will start charging. Even though it is single wire, IIRC that refers to a single charge wire, I beleive there is still a smaller plug with the sense wire. On my work laptop at the moment so I don't have the info handy. Look at some of the wek sites with they DIY generators where people hook them up to lawn mowers and such, one of those has references for the various different models.

If I am not mistaken this was the problem. There was a small two prong plug hidden underneath a rubber plug. I removed the plug and ran a jumper wire back to the main + wire coming out of the alternator.To "excite" the alternator. This got the system to charge.(once the engine rpms raise a bit)
Should I put some sort of diode inline on this jumper wire to prevent any "back feed" from the battery? Will this be neccesary?