Does anyone know how to test a power door lock switch to see if its bad? I keep blowing a fuse whenever I plug the switch into the pigtail. The circut is fine until I plug it in..

The ground for the power door lock system comes through the right door switch. There are two black wires comming from the plug that go to a lug that is screwed to the door frame. You may want to remove this screw and see if it still blows the fuse.

If you have an multimeter and a wiring diagram you can measure the switch contacts for continuity. If you do not have a diagrame let me know, I will try to post a picture of the switch and its contacts.

So, your saying that the ground itself could be bad...Im going nutz with this. Ive gone so far as replacing the entire dash harness. Imagine how discouraged I was after spending big $ on the harness and the darn courtesy fuse blew again.....Id appreciate anyone elses input too.. Thanks

Dan

|UPDATED|10/1/2003 4:35:16 PM|/UPDATED|

Not exactly. The switch plug is wired as shown below

CONTACT WIRE FUNCTION
A ORANGE FUSED 12 VOLTS INTO SWITCH
B BLACK GROUND INTO SWITCH
C PINK 12 LOCK OR UNLOCK TO DRIVER'S SWITCH
(I can nor remember which)
D PURPLE 12 LOCK OR UNLOCK TO DRIVER'S SWITCH
(I can nor remember which)
E BLACK GROUND INTO SWITCH

Since the under dash harness has been replaced I would start by checking each of the above wires with an Ohm meter to verify that they are going to the correct place.

If your switch is shorted and connecting contact "A" to contact "B" or "E" the fuse will blow. So my second step would be to disconnect the lug (on the end of the two black wires) from the door frame and see if the fuse blows.

Im not very versed in electronics, but when we were checking for a short, we were getting a negative reading on the orange lead.....I think this means that the orange is touching ground. Is that correct.....

I have the NCRS wiring diagram book and according to that, everything is connectd properly....
Dan

|UPDATED|10/3/2003 9:08:01 AM|/UPDATED|

When you got the negative reading, were you using a volt meter with the (+)red lead on the orange wire and the (-) black lead on ground? If the leads were reversed you would read -12 volt rather than the expected +12 volt.

I have posted a diagram of the switch contacts on
http://f1.pg.photos.yahoo.com/lcd79vet With the diagram and your Ohm meter you can check your switch.

But, with the fuse out, should I be getting any reading on the orange wires at all???? Your diagram looks just like the one I have in the NCRS wiring book. Do you think it has anything to do with the fact that my vette was an early production 79.....perhaps I should look at the 78 diagram. Any further help would be greatly appreciated...

Dan

According to my diagram if the fuse is out you should not measure any voltage on the orange wire. I am going to replace the passenger door switch on my 79 tomorrow. I will measure the voltage on the orange wire with the fuse in and out. I will post the results tomorrow night. My 79 was built in October of 78 and it matches the 79 wiring diagram.

What voltage value do you measure (+12 or some other value)?

I measured the voltage on the orange wire at the passenger door lock switch.

1. Fuse in: measured +12.3 volts
2. Fuse out: measured +0.5 to +0.6 depending on where I connected the negative (black) lead of the meter (ground).

How come I aint got no power door lock switch?