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Discussion Starter · #1 ·
*If any mods think this applies more to Fords than snowplowing, please move to the appropriate location.*

Here's the problem. When I shift into reverse with my plow on and then angle or raise OR angle or raise (in drive) and then shift into reverse my voltage drops to "N" ("normal" on gauge, no numbers) and doesn't come back up until I shift into drive. The voltage is normally between the "M" and the "A". I just put in a new battery and alternator a few weeks ago. I have no clue what to even check. Without the plow hooked up when I shift into reverse the voltage drops a little, maybe 1 volt. Any thoughts would be greatly appreciated!

This is on a '97 Ford 250HD, 351, E4OD with a Western Uni Mount 8' Pro Plow.

-Tim
 

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Do you have aux. back up lights on it? The volts will drop a little if you do put the truck in reverse. Mine does although it is a Chevy. I don't think you should worry about it, unless it is a severe drop in volts.
 

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I think that is fairly normal, my trucks do the same. I guess it takes alot of juice to power 2 back-up lights and the brake lights if your foot is on the brake at the same time.

Ray
 

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When I read the topic title, my guess is that you have auxiliary backup lamps and it does sound like it. A pair of 55watts lamps would draw around 9 amps. Are you running some lightbar of kind? I understand that lightbar would be running at all the time, but it could be possible that you may have too many electrical circuits running at the same time that your Ford electrical system might not be able to keep up with it.

If it drop about one volt or less when backing up (even though it really should not), but not below 13V, maybe 12.5, then I think you would be fine as long as the voltage come back up once you shift the truck to forward. If below that voltage, I would not take that chance and get the electrical system checked out. Maybe trying to limit using the aux. backup lights (if your truck have it) by turning it off with a switch.
 

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Why don't you make up a cig lighter plug on a digital multimeter, so that you can actually measure the voltage during these conditions. That might help us solve your problem. Those factory gauges are not much better than "idiot lights".
 

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Discussion Starter · #6 ·
I completely forgot about the backup lights, what an idiot I am. I do have 2- 55 watt lights tapped into the reverse light wire so they go on automatically. I do have a small strobe also. I don't remember it doing that previously but maybe I've been looking at my voltometer lately more than I used to.

It does only drop about a volt without the plow hooked up, but with the plow on it's gotta be dropping at least 4 volts, I guess and that's my concern. I just get concerned with the volts being so low and backing down a steep driveway and not having the volts go up for a minute or so.

CPSS- Unfortunetly I'm not very knowledgable with electric but am interested in how I would make a cigarette lighter plug to hook up to a digital multimeter. I would feel better to know what's really happening and if I need to worry and get it checked out or not.

Thanks for your advise everyone. I still can't believe I forgot about or didn't think the back up lights at least contribute to this problem. I'll also check this weekend to see if the problem occurs without the back up lights.

-Tim
 

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It may be the sign of a weak battery. However there will be some voltage drop with that truck, seeing it only has a 95 amp alternator.

Geoff
 

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Dumb facts from the field.

You said you have a NORMAL guage not a voltage guage.

Both are pretty inconsistant. Digital multimeter is not necessary. Radio shack has a digital readout guage that plugs into the cig lighter I think this is what CPSS has in mind but I know he has a multi meter and probably uses this.

If you watch when you put the truck in drive or rev with you foot on the brake the voltage will drop because the idle speed drops.

High amp output alternators show this worse than standard ones.

So a drop with or without the plow on would be noticed but plowing drains the battery so it will show up more because the charge cycle is larger.

If you're worried get the digital voltage guage or borrow one and check voltage. If it drops below 12 V you have a probelm. It should be between 13.6 and 14.4 at Idle in Park, rev or drive.

Jerre
 

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Heres a digital multimeter from Radio Shack for $14.99. Multimeter they also have a cig lighter plug for $4.
Connect the + wire from the cig lighter ( positive, center) to the red wire of the meter, the - from the plug ( negative, shell ) to the black wire of the meter. Set the meter to the DC scale 20v range and turn it on. Plug it into the cig lighter of the truck and it will tell you the trucks voltage at a glance. You can leave it on while you drive.
 

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same thing happens with my duramax. Brakes on, reverselights on the truck plus 2 55w reverselights in the light bar plus the light bar plus the blade plus the heater plus the......well you get the idea........I'd say its normal. With brakes and reverse lights plus aux reverse lights and everything else thats normaly running thats a hell of a draw.

I have my aux lights wired off my revers lights with a relay. I didnt want to draw all that juice through the reverse wires.
 

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I have a question for all of you. I also have two 55w reverse lights mounted on the back of the truck. They are tapped in to the reverse wiring direct (no relay). I dont have the stock reverse lights hooked up, because I took them out to mount hide-a-way strobes. Is it better to hook them up to a relay instead of the direct wire method? Does directly wiring them draw too much power through that circuit? Thanks for the help.

Matt
 

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Matt, it depends on the truck. Some of the stock reverse light switches seem to be able to handle the extra current OK. I would perfer the relay because you could then run a nice big 12 or 10 gauge wire to the battery (with a 20A inline fuse at the battery), and not worry about melting the stock reverse light switch, or any voltage drop problems.
 
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