Wiper issue has me scratching my head

[GMCSTEPS]

Installing a new wiper motor in the 65 today, old one was blown out so time for a replacement. Bench tested the new motor and it functions as it is supposed to. However when I installed it and plugged everything in, nothing.

Ok first thought is power or ground issue, so I pull out the volt meter and go to work. Here's the kicker - meter is showing 12 volts at yellow wire at wiper, and blue wire showing continuity to ground when switch is in on position, nothing in off position - seems to be functioning as it should. With motor installed the body of the motor also showing to be grounded.

I tried a jumper wire from yellow wire to motor (which shows 12v with ign on) and jumper wire directly to ground and the motor did not work. I can't figure out why, with 12v showing at the yellow with ignition on and motor jumped directly to ground why the motor would not kick on. Wires are hooked up the same way I originally bench tested to motor. Any help is appreciated as I am out of ideas at this point

[WOLFMANmike]

Originally Posted by GMCSTEPS

Installing a new wiper motor in the 65 today, old one was blown out so time for a replacement. Bench tested the new motor and it functions as it is supposed to. However when I installed it and plugged everything in, nothing.

Ok first thought is power or ground issue, so I pull out the volt meter and go to work. Here's the kicker - meter is showing 12 volts at yellow wire at wiper, and blue wire showing continuity to ground when switch is in on position, nothing in off position - seems to be functioning as it should. With motor installed the body of the motor also showing to be grounded.

I tried a jumper wire from yellow wire to motor (which shows 12v with ign on) and jumper wire directly to ground and the motor did not work. I can't figure out why, with 12v showing at the yellow with ignition on and motor jumped directly to ground why the motor would not kick on. Wires are hooked up the same way I originally bench tested to motor. Any help is appreciated as I am out of ideas at this point

this may be a stupid question but did you make sure that the motor is no binding up on anything while its bolted to the firewall ? i would say hook up all the wires factory the way they are normally run and dont bolt it up to the fire wall yet . then while in you hand try to operate it . if it works right then something has to be making it bind up on the firewall Happy Truckin

[GMCSTEPS]

Hey Wolfman, thanks for the response, I did think that it could be something binding, I unhooked everything and tried it again, and still nothing. Also tried running a ground jumper to motor casing while disconnected and still no dice.

[WOLFMANmike]

Originally Posted by GMCSTEPS

Hey Wolfman, thanks for the response, I did think that it could be something binding, I unhooked everything and tried it again, and still nothing. Also tried running a ground jumper to motor casing while disconnected and still no dice.

ok maybe the issue is in the switch .. maybe its gone bad ?

[GMCSTEPS]

It's possible that the switch isn't properly grounded but what is strange that with the power connected directly from wire to motor and manually grounded out, motor will not engage, but power shows to be a constant 12 v

[T and S]

I would try bench testing it again, maybe some thing went hay wire in the motor.

[chevy2tom]

Run a jumper wire from the switch knob post to ground. When I installed my billet powder coated dash I also ran into this problem on my 71

[chevy2tom]

In other words ground the switch itself

[GMCSTEPS]

I'll give that a try when I get in tonight and see what happens

Originally Posted by chevy2tom

In other words ground the switch itself

[forestb]

sorry ignore this post

[GMCSTEPS]

So update after some fiddling tonight. Turns out that voltage at the connector to the motor is actually between 10.5 and 11 but full 12.4 at the fuse. So getting close to 2 volt drop from the fuse to the connector. When connecting jumper wire from fuse block to motor directly, motor and switch function normally. I have not pulled the fuse block yet but expect to find corrosion or similar at the point where wire is connected to block.

1st Question is would that alone cause such a large drop in voltage and 2nd, does the motor require a full 12v to switch on?

[WOLFMANmike]

Originally Posted by GMCSTEPS

So update after some fiddling tonight. Turns out that voltage at the connector to the motor is actually between 10.5 and 11 but full 12.4 at the fuse. So getting close to 2 volt drop from the fuse to the connector. When connecting jumper wire from fuse block to motor directly, motor and switch function normally. I have not pulled the fuse block yet but expect to find corrosion or similar at the point where wire is connected to block.

1st Question is would that alone cause such a large drop in voltage and 2nd, does the motor require a full 12v to switch on?

im gonna say yes on both counts pull the box and give it a good look over and cleaning . then you should be golden

[GMCSTEPS]

Ok, finally had some time to wedge myself under the dash for awhile and do some work on the truck last night. I removed the fuse panel and the connections didn't look all that corroded at the fuse block for the wiper, but sanded them a bit and reinstalled it. After some more measuring with the voltmeter, this is what I finally came up with.

-With the plug connected to the motor and switch in off position, voltage shows full battery voltage at yellow wire.

-However, with switch in on position, voltage immediately drops to 0.

- with switch on on position, blue wire shows good continuity to ground.

The answer must lie in the sudden voltage drop with the switch turned on, but the question is, is that a ground issue or power supply issue? Ive done some searching about basic electrical troubleshooting but havent found anything directly related to complete voltage drop under load, any help is always appreciated.

[ray_mcavoy]

Originally Posted by GMCSTEPS

Ok, finally had some time to wedge myself under the dash for awhile and do some work on the truck last night. I removed the fuse panel and the connections didn't look all that corroded at the fuse block for the wiper, but sanded them a bit and reinstalled it. After some more measuring with the voltmeter, this is what I finally came up with.

-With the plug connected to the motor and switch in off position, voltage shows full battery voltage at yellow wire.

-However, with switch in on position, voltage immediately drops to 0.

- with switch on on position, blue wire shows good continuity to ground.

The answer must lie in the sudden voltage drop with the switch turned on, but the question is, is that a ground issue or power supply issue? Ive done some searching about basic electrical troubleshooting but havent found anything directly related to complete voltage drop under load, any help is always appreciated.

The fact that you're seeing the voltage on the yellow supply wire drop from full battery voltage down to zero when a load is applied indicates a power supply issue.

I'd recommend taking another good look at your fuse box. With the wipers switched on, try wiggling the fuse and/or sliding the fuse side-to-side a little bit. It's not uncommon for there to be a bad connection between the fuse clips and the fuse even though everything looks relatively clean and corrosion free.

[GMCSTEPS]

So I went back through and checked everything starting from the fuse box all the way to the motor checking for bad connections, broken wires or anything that could be causing this issue. Everything including the fuse looked good and solid, but in a last ditch effort decided to pop a different fuse in just to make sure even though the fuse looked good.

BINGO! after replacing the fuse, wiper worked like a charm, exactly how it is supposed to. The fuse must have been partially blown/corroded, allowing enough voltage by to show on multimeter, but not enough to power the motor. Moral of the story is that even though a fuse looks good and is giving a voltage reading, try changing it anyway. Thanks to all who lent a hand, its what makes this community great!

[61K10]

post a pic of the plug? on my 61 you could plug on backwards? 61 motor is a little different though. Isn't the B power constant at the motor and grounding turns it on? do you have a ground wire from the w-motor to fire-wall/dash?

[61K10]

I had one like that on a motorcycle. Glad you are wiping now lol!