Electrical Diagram Experts?

SeaDweller · 06-04-2002, 12:41 PM

I'm trying to track down the cause of a dead cigarette lighter. Being that is uses the same fuse (#2) as the clock and interior lights (which both work fine), I'm assuming I can eliminate that as a possible cause.

Looking at the electrical diagram (which I'm really bad at deciphering), I can see where the hot lead goes to the fuse (#2), but I have no clue where the other lead goes. What is the "thing" that the red arrow is pointing to?

SeaDweller · 06-04-2002, 12:42 PM

By the way, #55 is the cigarette lighter......

911pcars · 06-04-2002, 01:03 PM

SeaDweller,
If the brown wire with the black(?) trace is source voltage, then the brown wire (your arrow) is ground (common ground). If you have a voltmeter, ground the black meter lead and connect the red lead to the cig. lighter terminal (brown/black wire). This wire should always be "hot" so the ign. key can be ON or OFF for this check.

If available voltage is okay (12 v), disconnect the fuse for this circuit, then use your ohmmeter (same terminal) to check for resistance/continuity to ground with the lighter pushed in. If no continuity or infinite resistance, verify you have a good ground connection, then replace the cig. lighter assembly. Basically, you want to verify there is a current path through the lighter to ground.

BTW, my lighter assembly provides a lousy connection to ground which results in an iffy connection to my cell phone charger.

Hope this helps,
Sherwood Lee
'69 911 "rs"
http://members.rennlist.org/911pcars

SeaDweller · 06-04-2002, 01:12 PM

Thanks Sherwood!

Can this be done by putting the meter leads inside the receptacle? Getting to the connections on this thing behind the dash would be nightmarish!!

If I have 12V present, then can I assume the ground might be faulty?

Early_S_Man · 06-04-2002, 01:17 PM

Hey, Dweller! why are you using one of those 'old-fashioned' geographic schematics? Current-flow diagram a bit too 'spaced-out,' huh?

The 'Thing' is a multiple ground connector!

I couldn't hurt to go through all of the dash grounds and clean & tighten them up by crimping the sides of the 1/4" Faston connectors slightly! Don't close the gaps completely!

This is essentially the same issue and remedy as for the 'dim' instrument lamps ... except there are alot more of the lamp holders, AND places for corrosion to sneak in ... a bit of silicone grease on the connections AFTER the repairs are completed wouldn't hurt to fight off corrosion for another 20 years!

SeaDweller · 06-04-2002, 01:23 PM

Thanks Warren,

Now, for the dumb question of the day.......Drum roll please...

Where are the grounds (Faston connectors) located, and what's the easiest way to get at them?

911pcars · 06-04-2002, 01:25 PM

I don't recall how this comes off the car (either front or back of dash). Try unscrewing the outer ring. If it comes out, then pull the entire assembly and wire loom as far as needed to test. Be careful you don't short the hot terminal to ground as you do this.

If voltage is available, then the circuit is good back up to the battery. The question is if there's a current path through the lighter assy. to ground. To check the ground connections, you 'll have to go in from the trunk. However, if the clock and other loads on this circuit appear okay, the lighter ground is probably okay too (don't assume too much when electrical troubleshooting; could be a broken wire). You could use a test lead and connect a temporary ground connection to the lighter. Doing all these little checks will allow you to pinpoint the cause of the malfunction. Blindly replacing parts is so much easier, but it always ends up more expensive if it's something else.

My lighter does this too. I should check it some day.

Sherwood