This question is for the electrically inclined.

My wipers will only work when I press the wiper button in either the low or high position. They will not continue to run however, just one swipe across the windows. With each press I get one swipe. I have replace the wiper switch with a new AC delco one. The wiper moter has been completely rebuilt and passes the bench test. Any thoughts or suggestions on where I should focus my attention to fix this problem will be appreciated. BTW, my vette is a 73 coupe.

Thanks,

Bret

Not sure, but it sounds like you may have a bad ground connection at the wiper motor. Have you tried running a jumper wire from the engine to the wiper mtr. case ? Other than that, it could be a bad connection at the 'pass-through' connection, where the fuse box is. My 2c.

Just another idea here to check. Is the upper half of your gauge console broken. If so, the switch itself it losing its ground. Once you push the wash button you make the upper half touch the bottom half and the wiper makes its pass. Same as when you first turn the wipers on. This was one of the problems with my 70 when I was fixing things up.

Thank you both for the suggestions!

Eddie -

YES! my gauge console is broken in the usual place. Makes remove and install a snap. Did you replace the console or run a strap between the two?

Bret

Tried grounding the switch to the lower console, engine, and chassis. No luck.

Experimented with grounding the wiper motor housing. Did not fix the problem.

I checked the yellow wires on the motor and both have 12 volts. Checked ground continuity between black wire and motor housing. Good.

Any other suggestions? Is there a relay or something I dont know about?

Thanks,

Bret

Do you have a wiring diagram for your car?

|UPDATED|1/16/2005 6:03:29 PM (AZT)|/UPDATED|

To start with a bit of info on wiper motor operation.

The wipers are always hot with the key on. This is the yellow wires going to the wiper motor. The wiper switch grounds the motor to operate. The high speed winding in the motor operates all the time the wipers are running, both high and low speeds.

When slowing down a motor there are two ways. First, cut the power to a lower level. But this will also reduce the power output, and that can't be done with wipers or the blades won't be able to move the debris on the window.
So they are run on high, and slowed down by adding low speed windings that operate in the opposite direction of rotation. This is called a shunt winding. It slows down the motor without reducing power.

The result, high speed runs at all times the wipers are on, and low is activiated with high for low speed. Both of these are grounded to activate.

I just checked my 73 diagrams. ( I have diagrams for 70 thru 75 if needed ).

The yellow wires are powered at key on through the fuse. The dark blue (dk-blu) and light blue (lt-blu) wire are the high and low speed windings. These go directly from the motor to the switch. The switch ground them. The black from the switch goes back to the wiper motor, and is grounded inside the motor, and then throught he motor housing.

The dark blue actually activates a park switch inside the motor to operate the motor when the switch is shut off, so the wipers will park in the correct position. Otherwise the wipers would stop at any point the switch is turned off. The dk blu wire operates the park switch, which operates one of the sets of windings in the motor.

IF the motor works on both high and low, even for one sweep, the connection between the switch and the motor is working. So the wires and connectors are making contact.

This seem to be the case. That means either the switch or the motor is the problem. The wipers return after on sweep due to the park switch, but the constant ground path is not being maintained.

You can jumper both of the wires at the switch to the black wire at the switch, and see if the motors continues to run on low. If so, the switch is bad.

You can then try the same jumpers a the motor itself. If it did not work at the switch and does at the motor, the wiring is making a poor or intermittent connection somewhere.

If it does not operate when jumpered at the motor, the motor has a problem internally. While the motor itself is okay it contacts may not be. The likely culpret is the park switch inside the motor.

So there are several test. Not all of the cars are wired the same, but that's you 73. If you would like I will scan and e-mail you the diagrams.

Excellent. Thanks Ken.

Yes, I would be most appreciative of a wiring diagram scan.

My email is: bhinerman@verizon.net

I have replaced the switch and had the motor rebuilt. I will run the checks you outlined and see what happens. What does the park switch look like?

Bret

|UPDATED|1/16/2005 10:46:43 PM (AZT)|/UPDATED|

this might be a dumb question, but is the wiper over ride switch on or off?

I will get it scanned in in the next couple of days and get it to you.