how to test ignition switch?

Decolliber · 07-08-2010, 06:39 AM

Turning the key in my 88 Carrera, nothing happens - no lights, and no start. The last time this happened (10 years ago) it was the ignition switch. The battery is fully charged.
I have done a quick search but could not find anything about the correct testing procedure for the ignition switch. Bentley explains how to remove it but not how to test it. I assume I need to first test for power going to the ignition switch.
Could someone give me sequence of steps to follow?

911pcars · 07-08-2010, 09:38 AM

Quote:

Originally Posted by Decolliber

Turning the key in my 88 Carrera, nothing happens - no lights, and no start. The last time this happened (10 years ago) it was the ignition switch. The battery is fully charged.
I have done a quick search but could not find anything about the correct testing procedure for the ignition switch. Bentley explains how to remove it but not how to test it. I assume I need to first test for power going to the ignition switch.
Could someone give me sequence of steps to follow?

Light and ignition circuits are separate branch circuits. Do the other electrical systems have the same symptom? If so, check the connections to the battery. If other circuits are functioning, I'd then check the fuses and fuse connections. Its unusual for two indepenpent circuits to die simultaneously. Look for common source. Lights and ignition receive source voltage from the fuse box. You'll need an electrical diagram to ID and track circuit routing. Do this methodically and in an orderly manner to diagnose this easier and faster.

To test the switch, use the aforementioned electrical diagram for reference. ID the circuit from fuse box to switch. Use a voltmeter to probe at various access locations in the circuit and different switch positions to confirm source voltage exists. Do this before chucking a good swtich.

Hope this helps,
Sherwood

Decolliber · 07-08-2010, 10:24 AM

Thanks for the advice Sherwood.

Browsing through the forum again I found a post from someone who had the same problem, and it turned out that the electrical plug from the ignition switch into the firewall had become detached. I checked my car and thats exactly what it was. Praise the Lord. Second time in 6 months that I have disabled my car by accidentally disconnecting a plug. Last time it was the plug for the CHT sensor in the engine compartment, and the engine would start and die ...

911pcars · 07-08-2010, 10:30 AM

Good catch. This forum is an invaluable resource of 911 info.

Sherwood