why no volt drop?
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Freshman User
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why no volt drop?
I have this setup on my '51 F1 (converted to 12volts) to drop the volts to 6v for the original 6v heater/blower motor. A previous owner installed a set of three napa-echlin volt drops wired in series from one to the other. I was never sure if this array was working so today I fed one end of the series with 12v from the battery and clipped my volt meter to the third volt drop to see what, if anything, was going on. I get 12.21 volts at both ends of this array; I expected perhaps 7.7 volts at the output end. I had three new volt drops left over from my '49 mercury project (same napa echlin product) and tried 'em again; still 12.21 volts at entry & exit. These volts drops all look good and no evidence of overheating, so why can't I get near 6 volts? Do I need to wire the heater motor up and see if the volt drop occurs at the motor?
Postmaster
Joined: Mar 2000
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From: Waynesville, OH
You answered your own question. If the voltage dropping units you are working with are just resistors (as I suspect), you won't see any voltage drop until you put a load on the last one. The amount of voltage drop you see will depend on the load you install. Then again, if you put too big a load on them (too low a resistance), you'll have three little pieces of stuff that used to be voltage dropping resistors.
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Okay Thanks. I will hook up the blower motor and see if I can fry anything. (Everything all apart...heater & motor in shed...volt drop on workbench in shop...bare cab in barn sitting on the frame with fresh paint...fresh flattie on engine stand in shop...all going back together next week.)
Posting Guru
Joined: Apr 2004
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From: Seattle WA.
If you are still running the Magic Aire Heater why not just install a 12V motor. It probably wouldn't cost much more than a GOOD volt drop unit. I pulled the Magic Aire in my 51 F1 to clean and paint it, I was suprised to find it had a 12V motor in it already.
And if you paint yours be careful what you use inside of the unit. I painted mine with a rust preventing paint and it made me half sick every morning on the way to work for 8 months.
And if you paint yours be careful what you use inside of the unit. I painted mine with a rust preventing paint and it made me half sick every morning on the way to work for 8 months.
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Yes I've considered updating with a 12v blower motor; that's what I did to my '49 Mercury. A 12v Ford Falcon blower motor fits nicely. Just trying to learn something about how these volt drops work; might need 'em to power up a 6v spotlight on this ol' F1. Thanks.
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Okay. Today I got the heater/blower-motor out of the shed and took it to my bench to see what is going on volt-wise. Using three volt-drops wired in a series I get 3.75 volts on high speed and 2.something volts on low. I could smell the volt drops heating up, but since I don't have a laser-type thermometer I don't know what the temp of the volt-drops was. I will try hooking up the motor using only two volt drops tomorrow and see what kind of voltage I get at the motor switch. How nice that everything is apart and I can work this out on my bench and not upside down under the dashboard.
