One wire alternator?

Cougar Community Classic Cougar Maintenance Restoration and Repair
1

I have a 1967 XR7 with a small block engine. Since adding an electric fan, I am seeing my amp gauge go all the way to the right when the fan comes on. This leads me to think that I need a more powerful alternator. I’ve been doing some research, and am thinking of going with a 100 amp (or more) single wire style alternator - I also have driving lights and a stereo amp, so the stock alternator may just not be keeping up with all of this.

It looks like a simple conversion, but my question is, will this affect the operation of anything else - especially the stock tach? It appears to me that I’ll need to convert my amp guage to volt gauge, but just didn’t know for sure about the tach (or anything else, for that matter). Anyone here done this conversion? Anything else I should know from your experience? I would assume there should be an inline fuse from the 1 wire alternator to the battery - what amp fuse should that be?

Thanks!

2

It won’t affect the tach, but your ammeter will not work.

3

Good article here on a GM swap. Cougar Club of America - Tech Library
Also attached a PDF of the article.

I believe some have also used a late model Ford alternator.
GM-alternator-swap.pdf (231 KB)

4

Hey, thanks for that article and info Midlife and zman. My only other question is - does that sound like I probably need a higher amp alternator if the amp gauge needle goes all the way to the right with everything (stereo, driving lights, electric radiator fan, etc.) on? At idle it goes down a little, but at cruising speeds it is buried all the way to the right.

5

Oh wow. Most ammeter needles never move. What you describe sounds to me like a wiring issue more than anything else: probably a bad connector near the starter solenoid. Or a bad OEM splice, or even a bad PO splice underneath the tape on the headlight harness. Probably the latter.

6

I went with a 100 amp alternator but I wired it up as a three wire. I used this article to make my decision.

http://www.madelectrical.com/electricaltech/onewire-threewire.shtml

I also spoke with the author, Mark Hamilton, on the phone and he mentioned that the original AMP gauge could be used with the three wire set-up. I chose not to. But you might consider it.

7

i installed a 150amp powermaster. The unit come with a nice wire, but i installed this fuse as well

http://www.summitracing.com/parts/aww-500689

i went with the one wire setup straight to the starter solenoid. Some self tapping screws from hardware store helps for fuse pack install.

been 8 months. I’m still very happy with the purchase. even left my parking lights on overnight. car fired right up. squealed like a pig of course.

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I drove my 69 at night today and the alternator didn’t seem to want to keep up with the headlights on. The dash turn signal indicators wouldn’t flash and they do with the headlights off. Is there anything you guys ran into doing the conversion that could give me trouble?

9

I think a new ALT setup would correct that. If you’re running halogens then that could be causing the issue. Before i switched over, my turn signals would go slower at idle. The headlights would also pulse with engine rpm. I also feel like the engine did not run as well with the old setup. I would have got a 100amp if i wasn’t running such a big stereo. So i got the 150

10

I’ll be switching alternators pretty fast now anyways but I think my tail light wiring small messed up anyways so that’s a separate issue haha