Hi I have a 1953 Chevy truck with a 235 Eng and the generator. My question is that I have to convert to an alternator to install an electric fan, I don’t understand what I need to do to the amp meter . Some people say it will be ok others say it will get hot . How do I fix this problem, or can I bypass it completely. Thxs
I've been driving my '37 for 26 years with a stock amp gauge, alternator, and recently installed A/C. With a good battery and proper sized wires, the amp gauge should stay right in the center, it will go to charge after start up while the alternator recharges the battery, but it will fall back as the battery recovers. Any accessory should not alter the amp gauge once the alternator catches up to the draw on the battery. My truck has HEI ignition, all the lights of a normal truck, a few add on gauges, A/C compressor clutch, and A/C blower motor. I have a small fork truck style alternator that puts out 40 amp max, I've never seen the amp gauge above about 10 or so and that's only after it has sat for weeks not started. The amp gauge is in its own metal housing, so I have no idea if it gets hot or not. The A/C pulls power at start up, but once running the amp load is pretty low, same for the HEI, head lights are probably the biggest users of power.
We would need to see the wire diagram to figure out how to bypass the amp gauge for the electric fan. The alternator should see any draw on the battery, so even relays won't help. Pulling power off the alternator before the amp gauge might work.
If you are worried about the heat, just put it together and try it while checking the gauge with a heat gun
VERY UNLIKELY that you will overheat the amp gauge. It consists of a shunt that serves as a slight voltage drop that the actual gauge measures that voltage drop across it. I suppose if your alternator exceeds the rating of the amp gauge it might peg the meter, but unless you've exceeded the carrying capacity in amps of the wires connected to the amp gauge, you don't need to worry about overheating. If you're worrying about that, you can connect the alternator output wire to the battery side of the amp gauge, but then you'll have no indication of whether your battery is getting charged. Same with a high amp load, like the electric fan, whose circuit feed can be connected directly to the battery (put a fuse in that connection for protection.)
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Can I run the output wire from the alternator to the battery directly skipping the amp meter
As I already said, yes, you can connect it anywhere on the battery side of the alternator. It doesn't matter where. But again, that won't give you any indication that your alternator is actually charging the battery. I think that would be a bad idea.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Here's an original wiring diagram for the 1953 Chevy truck. It has the generator of course, but you should be able to use it to figure out how how to hook up your alternator. But you'll likely need some information on the alternator itself.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
With a correctly wired system, any load placed on the battery will show on the amp gauge since the alternator is trying to keep the battery at full voltage. It doesn't matter how the accessory is wired up, if it pulls power from the battery the gauge will show it.
With the fan power feed coming off the alternator, it should not show on the amp gauge, it will go directly to the fan motor. This way, you're amp gauge will not show charge or discharge since the load is before the gauge. Not sure if its good for the alternator to work this way or not, but it would keep the amps lower through the gauge.
If you bypass the gauge you should at least install an aftermarket voltage gauge to keep tabs on the battery.
All accessories, ignition, lights, and what ever else you hookup, needs to be between the amp gauge and the battery. The alternator and/or generator needs to be on the other side of the amp gauge.
A single wire alternator ( self exciting ) is wired with the output lead directly to the amp gauge. The two wire is hooked up with main wire to the amp gauge and a trigger wire from the run circuit to alternator.
Your 14" fan will not take much power to run, just relay it off the battery with a toggle switch to turn on and off the relay, add an indicator light where you can clearly see it so you remember to shut it off when not needed. I would keep it high on the radiator and off to one side so it doesn't block air flow while driving as most in-front fan do. An easier method of cooling at idle is to simply increase the idle speed when its hot, an electric idle solenoid on a toggle switch would be easy to hook up and would increase the idle rpm a couple 100 rpm when needed. Or do as I do, when the temps start getting warm, I speed up the idle 100 rpm to compensate for the A/C, during the winter, I slow it back down.
Joe H has it pretty well mapped out for anyone to find the best option that suits them. You will need a voltmeter. Some of those trucks have a cig lighter. There are plug in voltmeters that work well.
~ BD. "You won't find me in an old folks home" Pioneer Florida Cracker 1958 Apache Stepside 1958 Apache 1/2 ton Panel 1959 Apache 1/2 ton Panel
i have seen alternator and generator interchanged in this thread. And not sure the original thought of even having to convert from generator to alternator was properly addressed for those that may come across this later . The amp gauge was addressed it looks like.
Sal3167 based on your original post do you have the generator if so are you planning to convert to alternator? or do you prefer stock generator?
My truck has a 63 amp alternator and I installed a second shunt, as suggested by HotRod Lincoln to prevent a fire caused by a faulty ammeter. Fabricated from a SS hose clamp, bridging the positive and negative terminals. It does show charge/discharge but not the actual value.
In the process of doing the bodywork/paint, I reduced the size of the center section of the shunt from 1/2” to about 1/4” (no photo) hoping it will show more of a swing. I’m not looking for actual value, but more of an indicator of the health of the charging system.
We’ll see when I fire her back up in May.
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
I was reading about fans, a couple guys said 10 amp draw for every 1000 cfm of air flow once running, and 2.5 times that amp draw at start up. The start up draw will be be for a very short time, like milliseconds. These are average numbers, so a 2000 cfm fan will pull around 20 amps while running. They also recommend looking at the stated amp draw verse the cfm ratings when shopping, if they don't fall into the 10 per1000 rating, they spec's are likely wrong, either more amp draw than stated, or less air flow than stated. My guess is a 14" fan will only use 10 to 12 amps while running and probably do very little to help cool the engine. The amp gauge will be just fine as is.
