sixtyfour

Well guys, thought this would be simple....but:

on 1964 olds cutlass 442 my windshield wiper blew the fuse, ok replaced blew again. OK, run a direct jumper from battery to motor, works like a champ. So I have a short, tried to find, but hard to locate. So I remove the wiper switch from the dash, and it is one lead, checks out ok, so I figure it completes the ground to the motor, np. So I build a jumper from the battery to the wiper motor and place the switch in the loop, OK. But now I reattach the battery cables and it frys the wire on the positive side of my jumper??? Is my wiper motor maybe shorted ??? not sure whats going on hoped on of you guys has schematic

For christs sake Im an elec engineer,,,, what a loser Grin let me know if you have any ideas

Thanks Sixtyfour

jaunty75

Given that the wiper motor works OK when you run a wire directly to it from the battery, it would seem unlikely that the wiper motor itself is shorted. But since fuses are blowing, it seems you have a short in the circuit somewhere.

I've never been a fan of jury-rigged wiring specifically because of what happened to you. What you're doing may ultimately result in damage to the car and/or serious injury or worse to you.

It would be much better to trace the wiring and find the short. If you don't have one, you might also find the 1964 factory service manual helpful as it has an extensive section on the wiper system operation with wiring diagrams and troubleshooting sections. If you don't have a manual, you can find one online for free at wildaboutcars.com. The section you want starts on page 13-54.

MDchanic

+1. GM wiper motor designs were "interesting" to say the least, but should be manageable to an EE.
The Chapter on wipers goes into the motor's operation in painful detail and should help you out much better than we could.

- Eric

sixtyfour

Hey guys,

Looks like my motor is toast, OPGI has a listing for part # CH28544 but it doesn't look the same. My motor looks rectangular and not round looking like theirs. Any ideas on where to score another one?

Thanks

Sixtyfour

MDchanic

Is it this one?





$80 at Advance Auto, $120 at NAPA for a Cardone reman.

$180 from OPGI is insane.

- Eric

sixtyfour

Yep looks like it, found one on summit for $94 bucks, will keep you guys posted - Thanks for the help!

MDchanic

Advance Auto, and probably O'Reilly's and AutoZone, will be cheaper, and no shipping costs.

Almost definitely the same Cardone part from all of them.

- Eric

sixtyfour

Ok guys,

I checked the schematic and indeed the on/off switch goes to ground to complete the loop to turn on and off. Switch checks good - but every time I engage the switch it blows the fuse which flows from the positive side of the battery. When I take jumpers directly from the neg of the battery and the pos side of Battery, it runs great??? So one would say I have a short either in the motor or the pos side of the power. One of my questions is - is the motor insulated from the chasis ground? Doesn't show it on the schematic yet how does the switch to ground work if the motor is grounded to the chassis? I guess I'm looking for a olds wiper motpor guy that understand what it should act like. Right now I just using a lot of fueses and burning lots of test leads up. And I have bought another rebuilt motor but it acts the same... so???


Anyone out their?

Thanks Sixtyfour

rjohnson442

sounds like the switch is shorted out not the motor if it blows every time the switch is used instead of jumping it.

Grace Stinespring-Welch

x2 on the switch,or even a shorted wire.

MDchanic

You have a conundrum here.

According to the diagram, the wiper motor has 2 wires, with one more for the washer.

Purple wire goes from 20A wiper fuse directly to wiper motor.
Green wire goes directly from wiper motor to switch, and then to ground when switch is On.
White wire goes directly from washer solenoid to switch, and then to ground when switch is pressed.

If there were a short in the motor or the purple wire, the fuse would blow, but it would blow all the time, whether the switch was On or Off.

If there were a short in the green wire, the wipers wouldn't turn off.

If there were a short in the white wire, the washers wouldn't turn off.

I can see no place for a short or a bad connection that would cause the fuse to blow only when the switch was On, and at no other time, especially since the motor works fine otherwise.

Are you using a 20A fuse?

- Eric

sixtyfour

MDchanic,

Yep your correct, what makes it weird is if the switch, which tested good is off it doesn't blow the fuse. But when switched on it does. If you use the switch which goes to ground and wire around the purple with a direct lead, it blows when turned on. But if you run two seperate leads from the battery to the wiper motor, it runs like a champ?? I would like to know if the motor its self is ground to the chassis, the motor sets in rubber gromets and has a insulator ring on the inside, so I'm not real sure.

MDchanic

I would double check the fuse value, and then run the motor with an ammeter in the circuit (has to be a decent-sized one) to see what the current draw is when running.

- Eric

sixtyfour

Well folks I figured out what happened. after getting the spare motor I did some experiments since both act the same. It turned out to be the positive and the negative were reversed. Not by me, but while their for what ever reason I had it in to get a new clutch and pressure plate installed, during ut after fixing the leads and putting back together it works good now. Guess I'll keep the new motor for the spare since they scarce, only about $100 bucks.

Thanks all of you for helping me think this one out, the schematics helped

Sixtyfour

MDchanic

I'm confused.

Why would reversed polarity in a DC motor cause the fuse to blow?
Normally, this would be expected to make it turn backwards.

Glad you fixed it, though!

- Eric

sixtyfour

MDmechanic'

I agree with you, but that's the way it shook out. Maybe the motor used some capacitor to help it from drawing to much current on start up? that would assist the peak draw on current to the motor. Might explain why they used chassis ground to control the wiper motor while everything else uses the positive side??? Not sure, but that seems to fit, could be wrong.

But thanks!

Octania

Pretty sure capacitors don't do much for DC circuits

EE eh?
:-)

The motor IS typically grounded- via that strap seen in the photos above, from motor to mtg screw.

Glad you got it all fingered out
My suggestion was going to be inspect innards of the fuse block- restoring a '66 442 I had all the wiring out and was refreshing the fuse block and noticed that one wire had chafed thru the insulation and was able to or ready to short to another wire. Imagine the headaches there, depending on exactly what circuits are involved.