Basic Electrical Question

[jpearson]

The windshield wipers on my car have been inoperable since I brought it home. After checking the fuse my next stop is the wiper motor. My question is can I just hook my car battery up to the wiper motor to check it? Is there a better way?

[Danny_Ocean]

Yes, the motor is 12vdc.

Better way is to use a test-light to see if the motor is receiving 12vdc.

[DRACO A5OG]

You may be missing or have faulty Wiper Contact Switch



Does your horn work?

[jpearson]

Thanks Danny - that's two of my questions you've answered in the last 24 hours (San Diego shop was the other).

[porschenut]

There's a relay mounted to the tub underneath the wiper motor. If the motor itself checks out, my money's on a failed relay.

[jpearson]

Draco - the horn does not work. I'll pick up a test light and check out the motor first.

[timmy2]

Spend the money on a decent digital combination volt/ohm/amp meter. You'll need it with these cars if you want to troubleshoot electrical safely and properly. The light will help too for simple circuit checks.
Have a fuse in line with the power from the battery when you use it for applying test voltages.
I work on 500,000 volt equipment but a car battery will kill you just as fast!

[jpearson]

I'm planning on getting a multimeter. I didn't make it to the store. I started trying to get to the wiper motor but getting past the blower equipment is taking longer than planned - it doesn't help that I'm screwing' around on the computer now.

[DRACO A5OG]

Originally Posted by jpearson

Draco - the horn does not work. I'll pick up a test light and check out the motor first.

Okay, you found the most likely suspect, remove the steering wheel and check the contact switch,to see if it is connected and the ground also is connected. the wiper and horn will not work if this component is disconnected or broken.

Also check to see if the round relay at the fuse panel is plugged in, it should be number 3 plug, check your fuse panel cover for it's location.

Jim

[jpearson]

Draco - I pulled the steering wheel today. They wiper switch looks good. The metal strip is intact and relatively clean the the wire was connected on the back. Anything else I should look at on the switch? I didn't have time to look at the motor yet.

[DRACO A5OG]

There is also a ground connection at the bottom right mounting screw of the clam shell half.

Ground/close the switch to see if the horn sounds. If not, check to see if the round relay is plugged in at the fuse panel?

Swap the relay around to confirm it is not the relay.

[Neel]

http://forums.pelicanparts.com/porsche-911-technical-forum/440814-electrical-troubleshooting.html
This may help also...

[jpearson]

So I need a little more edumacation.

I went to buy a test light and after discussing what I was doing with the hardware store guy he said I needed a continuity tester. After getting home and reading about how the tester works I'm confused. I have a hard time conceptualizing electrical problems so let me explain how I was thinking about the problem and then you can explain the error of my ways.

In testing the wiper motor I thought the idea was to see if power is going to the motor when the wipers are switched on. There are then two possibilities:
A - Power is getting to the motor - this would indicate the motor is not working.
B - Power is not getting to the motor - this would indicate that something else is at fault and really give me no information about the motor.

The continuity tester doesn't look for existing power but rather creates its own to look for a complete circuit. How does this help me? If there is a complete circuit through the motor does that mean that the motor should work? Or did I buy the wrong kind of tester?

Also there are several wires to the motor - which ones do I test? The red/white wire comes from the fuse and brown goes to the ground - are these the wires to test?

Thanks

[timmy2]

Get this meter or one of equivalent quality and read up on basic electrical testing.
NEW FLUKE 15B F15B Digital Multimeter w/ Carry Bag | eBay

[Neel]

Josh, post#12 will guide you to find your problem.. However, as Dennis says above, you need to read up on basic electrical testing and get a meter.. The Fluke he posted to is simple to operate and 'a lot of bang for the buck'.

[HarryD]

Originally Posted by timmy2

Get this meter or one of equivalent quality and read up on basic electrical testing.
NEW FLUKE 15B F15B Digital Multimeter w/ Carry Bag | eBay

You can get by with one of these as well for a lot less:

Digital Multimeter - Save on this 7 Function Digital Multimeter

[timmy2]

Originally Posted by HarryD

You can get by with one of these as well for a lot less:

Digital Multimeter - Save on this 7 Function Digital Multimeter

True, Harry, it is cheap. As a professional electrician I would never ask a person with limited electrical knowledge to even begin to try and use that. Multi scaled with limited protection for the user is not good for learning.
The fluke is almost foolproof with auto ranging and has built in safety features that protect the user.
Kinda like the difference between a 911 and a Yugo...
The on-off button looks good though...

[rnln]

timmy2,
can you please go into a little more detail of waht kind of protection you were talking about?

[timmy2]

Internal fuses comes to mind. The quality of a $5 meter is questionable. Leads fall apart etc.
Most people will end up using it on higher than 12 volt systems once they have the knowledge of how to use a meter.