Alternator draw??
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Junior User
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Alternator draw??
Hey all!
73' F250, 390, 2wd. I'm having a problem at idle with amperage going through my system. Basically.... when the blower fan is running and come to a stop (idle) my lights dim, the blower turns slower, etc. Even the blinkers start blinking slower to do an amperage draw- only when the fan is on. SO..... I've replaced the alternator, regulator, and the blower fan (with motor). Factory AC truck so getting to the blower fan is a pain in the butt. The alternator was replaced with a stock 60amp- Ford wiring. I'd like to convert to 100amp one wire at some point but for now I'm just trying to fix this issue before I throw more amps at it. Any recommendations? Thanks!
73' F250, 390, 2wd. I'm having a problem at idle with amperage going through my system. Basically.... when the blower fan is running and come to a stop (idle) my lights dim, the blower turns slower, etc. Even the blinkers start blinking slower to do an amperage draw- only when the fan is on. SO..... I've replaced the alternator, regulator, and the blower fan (with motor). Factory AC truck so getting to the blower fan is a pain in the butt. The alternator was replaced with a stock 60amp- Ford wiring. I'd like to convert to 100amp one wire at some point but for now I'm just trying to fix this issue before I throw more amps at it. Any recommendations? Thanks!
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Junior User
Joined: Nov 2015
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I was thinking the same thing. Will the wires be hot/warm if the wiring is faulty causing a hard draw?
Also.... I just found a problem with the ignition switch (lock cylinder). Sometimes when I start the truck nothing turns on in the dash. Fuel gauge, coolant gauge, radio, blower or blinkers. I had to wiggle the key and then everything turned on like normal I wonder if thats my issue on the power draw??
Also.... I just found a problem with the ignition switch (lock cylinder). Sometimes when I start the truck nothing turns on in the dash. Fuel gauge, coolant gauge, radio, blower or blinkers. I had to wiggle the key and then everything turned on like normal I wonder if thats my issue on the power draw??
Logistics Pro
Joined: Jul 2005
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If the draw is something that pulls a lot of current, or if it is drawing through some bad connections, that would heat the wires up.
Lead Driver
Joined: Mar 2004
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Sounds like some place in the blower motor wiring or switch it's getting a ground which would drag everything down like you say.
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
It is good to check everything that has been posted but that is what was wrong with the older ALT's, low out put at idle.
If you check the books it will only give output readings at a higher RPM (2000 RPM?) nothing at idle.
Even if you go with the 100 amp ALT it has the same low out put at idle but can have higher out put at 2000 RPM.
If you want higher out put at idle you will need to up grade to the new 3G ALT used on the newer cars & trucks.
It has the lower out put at idle needed to operate all the electrical on the new cars / trucks where everything is run by computers and they need a steady voltage to work right.
I am sure there is some poste of this up grade in here if to search for it.
Dave ----
If you check the books it will only give output readings at a higher RPM (2000 RPM?) nothing at idle.
Even if you go with the 100 amp ALT it has the same low out put at idle but can have higher out put at 2000 RPM.
If you want higher out put at idle you will need to up grade to the new 3G ALT used on the newer cars & trucks.
It has the lower out put at idle needed to operate all the electrical on the new cars / trucks where everything is run by computers and they need a steady voltage to work right.
I am sure there is some poste of this up grade in here if to search for it.
Dave ----
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Found it! Woohoo! Just wanted to keep you all updated with the solution. Turned out it was the ignition switch AND the ignition switch connector. The switch faulted which melted that funky looking harness. Replaced both and it seems to solve the power draw issues.
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
Those old cables and corroded connections are likely what roasted the switch.
Any alternator will be crippled from the get go from whatever its rated current output might be, with even just a tiny bit of almost invisible corrosion at a ground point or a connection. Just a tiny bit, an extra few hundredths of an ohm resistance, is enough to cause problems. It also "fools" the regulator into thinking the battery is fully charged up, when it really isn't. Make sure battery terminals, cables and ground connections are clean at both ends and tightened securely.
Any alternator will be crippled from the get go from whatever its rated current output might be, with even just a tiny bit of almost invisible corrosion at a ground point or a connection. Just a tiny bit, an extra few hundredths of an ohm resistance, is enough to cause problems. It also "fools" the regulator into thinking the battery is fully charged up, when it really isn't. Make sure battery terminals, cables and ground connections are clean at both ends and tightened securely.
Lead Driver
Joined: Jul 2017
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From: San Jose, CA
To add something to what FuzzFace said, when you get into the large case 1G alternators in the 70 and 100 (or 105) amp variety, they are well known for having more idle output capability than their smaller siblings the small case 1G units.
Though still not as good as the more modern 3G (or as powerful overall either) they are still an upgrade over stock. It was actually an upgrade option on some of our trucks, but I've seen very few over the years that were optioned that way from the factory.
I'm a bit jaded with old-school and love my 100a large case 1G. But even at that, when it finally gives up the ghost (or before even) I'm upgrading to the internally regulated 3G just because it is still a better unit. And less wiring clutter under the hood is never a bad thing either.
Now, to just install it and keep my ammeter functional, that will be the fun part.
Paul
Though still not as good as the more modern 3G (or as powerful overall either) they are still an upgrade over stock. It was actually an upgrade option on some of our trucks, but I've seen very few over the years that were optioned that way from the factory.
I'm a bit jaded with old-school and love my 100a large case 1G. But even at that, when it finally gives up the ghost (or before even) I'm upgrading to the internally regulated 3G just because it is still a better unit. And less wiring clutter under the hood is never a bad thing either.
Now, to just install it and keep my ammeter functional, that will be the fun part.
Paul
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