I've got some minor electrical problems in my vette, with some items not operating (horn, wipers, etc.) I was trying to figure out how to trouble-shoot these myself. I read the archives on the forum, and a few web sites on basic multimeter use. I still don't know what I'm doing.

For instance... I would like to see if the wiper motor is receiving power, or the proper amount of power. I learned from reading that I can check the volts by setting up the multimeter in parallel with the wiper motor circuit. Sounds great!

But wait, there are five wires coming out of my wiper motor? A three-prong assembly (gray, yellow, and orange wires), a black wire (the ground, I assume- it attaches to a terminal that grounds to a mounting bolt), and an orange wire on the opposite side which goes back into the main wiring harness.

Which wire do I touch the red multimeter cable to? The black one? How do I arrange them to test if the ground is effective? Can I have the motor removed, and simply touch the multimeter terminal to the ends of a pair of wires to complete a circuit, and test it that way, or must the motor be attached- thereby testing it in parallel? If I test it in parallel, how do I touch the multimeter probes to the wiring? Do I poke them through the wire insulation?

I know that this is basic stuff for most of you, but it is far from obvious to me!

Thanks for any help!

Matt :boxing

 

Once you set the DMM to 30V DC range, you should use the red lead to look for +V (battery voltage) and the black lead to look for -V (chassis steel). You will need a wiring diagram to determine what terminal on the wiper motor you should be touching and when it is energized or not.

The GM corvette shop manual has by far the best wiring troubleshooting guide in them. Try to pick one up specific to your year Vette on EBAY or order one from the catalog houses like Ecklers ZIP MAD etc...

Try to avoid poking the leads through the wiring insulation. Usually you can stick the leads into the connector contacts housing and be able to make a test connection. I have also modified my one of my many sets of leads to use straightened paper clips to fit into very tight spaces to make a connection. Just remember you dont want to physically ruin a connector from trying to take a V check.

If the car is not running, you are looking for 12.1 - 12.6V approximately(depends on the charge of your battery). If it is running , you should have 14V - 14.5V approximately.

Many of the newer DMMs have autoranging so you dont even worry about setting up the range but you must choose the DC or AC mode.

Brent...


[Modified by MN-Brent, 5:44 PM 1/19/2004]

 

Alright Matt ... A for effort. Most people would run from the meter.

Let's see ... all of above reply is true ...

If you can't get the probe into the connector to contact it, a last chance
effort is to push a sewing pin through the wire ... contacting it this way.

Check with the connector unplugged first. If no voltage there, then the problems are in the wire/switch/fuse. If you get power at the connector,
then I would certainly test it with the motor connected, too.

Check for the voltage at the connector. If it's good (>12v), then you can check
the ground connection by using the meter to check resistance (Ohms).
This may be denoted by the Greek capital letter Omega. Set the range to low,
(usually 200 Ohm scale) and place one lead on the black ground wire and the
other lead to a clean piece of metal on your engine (coil bracket,etc). The
meter should read close to ZERO - indicating a good ground connection.

Definitely get a book - or at least a wiring diagram to try and follow the
wires to the problem.

Good luck hunting
:seeya

 

http://iotech.no/corvette/technical/...tics/index.htm
Matt
Try the above link for schematics. :cheers:

 

Matt - I spent ages sorting out my 80's wipers. Now it's your turn to benefit from my weeks of swearing!
The other guys have outlined the testing procedures (checking grounds, voltages etc).
As far as the specifics of the wiper system go - I've just written some trouble shooting stuff for this system on another thread
http://forums.corvetteforum.com/zerothread?id=729069
which is completely relevent to what you're after, quite conveniently!
The wire colors may be slightly different, but the actual location in the plug (top middle bottom) should be the same for you.

Definitely download those schematics from the link above - they are worth their weight in gold (even if there are a few mistakes here and there!)

Happy to help a fellow 80 owner if you've got any more questions

Cheers

:cheers:

 

Hi Matt, I live in OKC also and would be willing to help you out. I work on electronics for a living, so I can teach you how to use your voltmeter. If you are interested, give me an email and I'll give you my phone number....Mike