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I have a 1973 F-100 that has a 360 under the hood. The alt is having a hard time keeping up with the load (from my added electrical components) and need something in the 100 amp range. Powermaster claims they don’t make one with out major bracket modifications.

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What are my options? Internally regulated is a plus.

Motorhome stuff?

3G from late model car

Other aftermarket brands?

Other?

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Thanks

 

http://www.lmctruck.com/icatalog/fc/0120.html

what are you running that you need so much juice

power doors and windows?

 

They don't sell anything over 60 amp for an FE, all the bigger ones are for 6 cyl, M's, and 460's

well the CD player, electric Rad fan, trailer brakes, CB, high torqu starter, etc.

Its the electic Rad fan that really does it, like when I am sitting in line for the boat ramp on a hot day.

 

i have the same setup except the trailer brakes but don't have any electrical problems and i have two battery's with a good isolator.

maybe check the fe forum for engine specific parts.

 

get yourself a new GM alternator from a parts store, we get around here for less than $50(core chrg probably applies) my buddy had 3 1000 watt subs in his 79 and had the same problem, then he fabbed up a simple bracket. The GM alts are a one wire hookup and are internally regulated. You can run duals and be worry free in case of incidence. It's an easy thing to do mainly because they are one wire hookup, but obviously you have to fab a bracket.

 

I would check with a local rebuilder. Lots of time they can "juice" yours up.

 

I really can't think of an electric fan that is made for pickup truck cooling purposes that takes more than the 60 amps that your alternator is rated at. Most 14-16 inchers take about 12-15 amps. So, if nothing else was going, it theroetically could run four of them - not that I'd try it and not that you need four. Could it be that you are spending too much time looking at your guage that could be wrong? Or, are you having to jump start this truck regularly? If the latter is the case then you really need to check the system and if you find something wrong it would be a good time to look into your 100 amp setup. If you just see your amp guage and volt meter move when the fan kicks on but haven't had to jump it ever, then thing are probably just fine. Do remember that you have a battery under the hood to kick in a little or a lot when the amperage load exceeds the output of the alternator. No worries, your alternator will charge it back up just as does when you start your truck as you drive down the highway.

 

352,
check the stamping on your alternator case to see whcih one you actually have.

Here are the OEM alts available for certain years.







Perhaps you have a VR problem instead ?


ps,You can get a 100 amp alt from a FORD van to install.

 

Yeah I have to jump start it occationaly. its usaly when I have been sitting at low engine speed and the fan is running constatly. The fan draws about 25 amps. As soon as the fan kicks on it starts discharing the batt, and depening on how long its on for is wheather or not I lose enought juice to need a jump next time I try and start the truck (assuming I don't drive for an extended perious after that to charge it up). Other than that everything is fine and charges great, it just can't keep up with all the accesories on.

I looked on the alt housing and couldn't find any of those numbers stamped into it. It is a Mortorcraft if that helps.

Being from a performance car backround I am used to seeing this problem a lot (hell my fox body mustang needs a 3g like something fearce) and an alt of 75+ amps usaly fixes it

The Van one you speak of, what years, engins, etc? Is it a never 3g that you are talking about?

 

It first sounded like you were scared off from powermaster because of bracket modifications. But every solution you have been presented so far seems to require bracket modifications. So if you are not afraid of modifying the brackets, you could put almost anything on it.

As far as the system you have now, I would measure the voltage at the battery terminals with the truck idling. It should be very close to 14 volts with the fans off. If it's in the low 13's, you may have a open diode inside the alt.

I would also be curious to see what would happen if you raised the idle speed a little bit. Your problem may go away if the alternator checks out good from the voltage test. I have a snowplow on my truck, and raising the idle speed was all that was necessary to get it to work with my stock alternator. I think it's a 60 amp too.

 

Yeah I was trying to keep this a bolt on project, but it always seems that all my projects end up with massive welding, fabricating, and machining. Even as something as simple as an alt swap. I think I am just cursed sometimes.

I guess I am just really surprised there is no direct swap for a bigger alt. I think I might throw on an AC crank pulley (they have 3 v’s) and space out the alt bracket to line up pulley on the alt with the furthest out “V” on the crank pulley. Then the powermaster alt should fit.

I still would like to hear if you guys come up with any other ideas.

 

That A/C pulley idea may work better than you think. Sometimes the pulleys from later models with lots of accessories had higher pulley ratios which would turn the alternator and the water pump faster. Check it out and see if the lower pulley is a bigger diameter. And you also may be able to find a smaller waterpump pulley to match, that will overdrive the waterpump(and mechanical fan if you still had one).

 

FWIW I have a chevy 1 wire on my 67 390, My Bud also has one on his 66 352 . It required nothing more then loosening the alt's bracket and swinging it up a hair and tightening it back down. No major prblem there at all.
You just need a bigger spacer in back ( to line the pulleys. I used a few washers), and your set. Dont cheap out on the connectors or the wire.

 

Thanks, I just tried a 130 amp 3g alt out of a 90's Taurus that I had kicking around for my foxbody mustang and it barley didn't fit. Do you have the part number/yearmakemodel/ or what ever for that chevy one wire that fits? How many amps does it put out?

 

I found that a small case 3G with the proper case fits great. I initialy ordered one from powermaster and it work great for 5 min. It then proceded to release all its magical smoke and die. Since powermaster said it was going to take over a month to get me a new one. I went down to the junkyard and for 10 bucks got a 95 amp small case 3g (looks identical to the powermaster alt) out of a 92 aerostar with wireing harness.


works perfectly, charges 14V at idel now matter how many accesories I have on.

you have to put a v-belt pully on it ( I bought one from powermaser, but you might be able to use the one off your fac alt), and I had to space out the pully a touch to keep it from rubbing on the case.