# Problem with plow headlights



## wxmn6 (May 23, 2001)

I have 1989 Toyota Pickup truck and I recently did all the wiring myself. I have experiences with wirings before so I was able to do the wiring for snowplow. I have a Fisher 6.5' Minute Mount snowplow which is guessed to be 1995 model year. So the plow lights system is 12-pins original headlamps system, not e-force. Today I tried to test the plow headlights system to see if it works. Some did work, some did not. 

On my first few attempts, when the headlamps is off, I tested the signals (left & rights) and hazard and they works fine. But when I turn the headlamps on, the lights on my plow is on and the lights on truck is off, which is the way it is supposed to be. Ok, when I tried to test the signals, when I tried the left signal, the signal light on left side of plow did blinks at its normal rate, but the right signal lights of plow also is blinking and it is blinking faster than normal. Also when I tried the right signal, it works the same way in opposition direction (right signal light of plow blinks normally while left signal light of plow blinks faster). When I tried hazard, a very weird and exciting thing happened. Both the headlamps on the plow and my truck is flashing like a police car! Both headlamps on plow flashs at the same time, then the headlamps on my trucks flashs at the same time, and this cycle continues. 

But later when I want to test again, the result was a little different. The results is the same as I said above on my first few attempts, except that the signals on my plow no longer works. So I tried again, and again, and I noticed that the right signal light is flashing very dim. 

I am fairly certain that I did not make any wiring mistake because I checked like 3 or 4 times before making connections just to make sure I don't make a mistake. I made 14 connections to three relays and am sure that it is connected at the correction terminals. The control stick and solenoid is not hooked up yet, but that does not matter because it have nothing to do with plow headlights. Also I did not have the battery cable hooked up to the battery, but again it have nothing to do with plow headlights, I think. 

The stuff I saw inside the sockets on plug is filled with I think dielectric grease, and in the plug from the plow, I am not sure what the stuff is on the pins but it is clear in color, maybe still a grease. What could the problem be? Bad relay? Bad wiring? Sorry about the long post but the more information, the better it helps to resolve the problem. Thanks!


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## 2401 (Feb 3, 2001)

No guarantee this is the solution, but a handbook on automotive wiring I have has the sentence "When electrical stuff works wierdly, look for bad grounds" in the troubleshooting chapter. I'd also be wondering about the relays, particularly if they are 1995 issue.

That's assuming all the wiring is OK, of course.

When you say the battery cable wasn't hooked to the battery, do you mean that the lead to the powerpack was disconnected or the truck's electrical system itself, with you checking the wiring out from a separate battery?


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## wxmn6 (May 23, 2001)

75,

The battery cable I was talking about is for the snowplow which will be connected to solenoid, not the truck's electrical system. I did not connect the snowplow battery cable to the battery because I am going to get a new heavy duty cycle battery someday. Thanks.


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## 2401 (Feb 3, 2001)

OK, that's one question answered. I would agree that shouldn't affect the lighting circuit either - the lights on my truck work fine right now and the powerpack ain't even ON the truck! (Dropped it off for a pre-season checkup/overhaul as required)

Wouldn't hurt to double-check for any wiring mistakes either. First time I wired my plow lights up I was SURE I had everything right, but managed to get a couple of wires wrong. If that all checks out, relays & grounds would be my next places to check.

One of the pins in the plug should be a ground connection, just like with trailer wiring. Check the truck side of that pin too - if the ground wire isn't making a good connection to the truck then everything is trying to ground through the mounting system. Since electricity always takes the "path of least resistance", when you operate your various lights the current takes different paths to ground, through other wires & lights!  Any relays that are tired will further add to the  

Hope this helps a bit - good luck sourcing down the problem.


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## CT18fireman (Nov 30, 2000)

Toyota uses a different method for powering the headlights. They use a constants power and two grounds one for high and one for low. Sounds like the plow system may be using this path for an alternate ground source. Did you tap into the truck headlights at the plugs or elsewhere? On toyots the headlights are seperate. I buss them together by running wires from the left light to the right and disconnecting the original right power source. If you do not have them wired together that could account for the flashing. If the wire harness wasa set up for a different vehicle you may have other problems. 
Contact me directly and maybe I can help you more.


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## wxmn6 (May 23, 2001)

75 and CT18fireman,

Thanks for your help. It turned out that there was nothing wrong with my truck and plow. I checked the wiring that I did and it is all connected at the correct terminals. I found out that I was supposed to drive in and connect the plow to my truck's pushplates. Yesterday I just simple connect the plug from the plow to my truck without pushplates on my truck because one of few bolts that holds the tow loop won't come off. I went to a shop today and they got the bolt out and helped install the pushplates for me. Then I got back home and tried to test the plow lights. The problem is still the same, but when someone told me to try to connect the plow to the pushplates and when I did, the lights worked perfectly. I learned that the plow have to be connected to pushplates so that way the system will be grounded.


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## 2401 (Feb 3, 2001)

It WAS a ground problem then, I never thought about the pushplates though.

Good to hear the problem seems to be "solved" - and that all your wiring was OK.


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## wxmn6 (May 23, 2001)

Yes, ground was the problem. Everytime when I backup my truck a little just enough for pushplates to not be in contact with plow frame, the headlamps start to flash until the pushplates is in contact with plow frame.

Unfortunately the problem seems to not be completely resolved. An hour later when I tried to test again to show someone else, the left signal light did not work. But the right signal lights still works. When I turn hazard on, only the right light flashes. I repeatly disconnect and connect the plug to the plug harness but no luck. Any idea what problem may be?


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## plowjockey (Dec 3, 2000)

The solution to this problem, at least to me it seems, would be to simply drill holes in the push plates and tap them and then bolt down a ground wire and the other end to your frame somewhere.

Still don't quite understand push plates (I have a fixed mount system) but that would give you a positive ground.

Just my $.02 worth.

Bruce

Come to think of it the ground wire could even be fitted with a watertight plug if your mounting system comes off at times during the season.


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## 2401 (Feb 3, 2001)

Bruce has a good idea with a separate ground wire & plug if necessary.

As for the left signal no worky/right signal does work, the same bulb filament is used for both functions. (Hazards simply flash all the signals at once) I've been tripped up by simple stuff before - first see if the left signal light bulb has "gone south". Of course, if you've already done that "please disregard this message"


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## wxmn6 (May 23, 2001)

Good idea about the ground wires. Sorry that I was not being specific, but I was doing a bit of experiment seeing what a difference when the pushplates is in contact and not in contact with the plow. Right now I don't have a problem with grounding when pushplates is connected to the plow frame. But in future if there is a ground problem, I know what I can do to help solve the problem. 

About the left signal light, I am not sure if there are one or two bulbs in the signal fixture. When I turn the park lights on, the left signal light did light up, but when I tried the left signaling, it did not blink. This problem is still the same when park lights is not on. If there is only one bulb in the signal fixture, then the problem should be between the wire connected to my truck's left signal light and the plow headlamp fixture.


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## 2401 (Feb 3, 2001)

Not sure how your lights are set up, my plow lights use a #1157 (dual filament) bulb, the signal light filament of the bulb is brighter than the parking light one. So if only one filament is gone, you could still have a parking light but no signal. Your lights might be completely different though - and something else that I have run across is a bit of corrosion buildup or a loose fit of bulb to socket.


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## Doc L. (Dec 24, 2000)

A good idea is to change all your directional and parking bulbs each year anyway. With the 1157 type dual filament bulbs the filaments break off and make contact with the other filament sometimes. Say a parking light filament breaks and touches the directional filament. Also with that little springy wire bouncing around it can cause it to work fine one minute and the next it's causing all kinds of problems. These type of bulbs don't last long on a loose or wobbly setup like a plow frame anyway as there is too much vibration. They aren't in a secure area like you'd have in your regular parking light location and the vibrations do them in all the time. A good bashing into a snowbank 2000 times a year doesn't help them much either. I was willing to bet you had a bad ground when I first read this thread and a good way to check it is to try hooking jumper cables between your lights and a good ground, however you said (I think) you tried that and they worked fine now and then intermitently it happened again. Like I said the filaments in your bulbs may be broken causing your problems.


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## plowjockey (Dec 3, 2000)

The jumper cable idea is a new on me but it sure sounds like a good way to check the ground.
I'll sure file that one away.

Bruce


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## wxmn6 (May 23, 2001)

I checked the signal fixtures on the plow and there are two bulbs in each fixture. Each bulb is #1157 dual filament. In the left signal fixture I found one bulb that have broken filament for signal light, and the other bulb was loose. I replaced the bulb and the signal lights is working. Right now it looks like my problem is all over. I will get some new bulbs as a spare for in future if some bulbs go bad. Thanks for your help!


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## screendors (Jan 23, 2010)

*Wiring Fisher plow lights on a 86 Toyota 4x4*

I am trying to wire my plow lights on my truck , I have a DPDT switch to go from truck lights to plow lights which works fine except I am getting aglow from which ever lights that are not suppose to be on. I know that the ground wires on the lights go to a positive ground when you switch from high to low beam, but is there a way of stopping the feed back to the lights that are not on. The only harness I have with the plow lights is the harness coming from the lights and they had a 4 pin connectors which I cut off and added a pair of connectors to disconnect. Hope someone can help.

Frustrated.


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