map light / dome light issue

[SteveJ]

The glove box light is wired to the instrument light circuit in the 260Z. (Ask the man/woman who ones one. )

No relays in the circuit. Maybe I can trace out the circuit next week when I'm in Memphis and far away from work. (Yes, I travel with a FSM. Don't you?)

[Scomell]

Hi SteveJ,

 

wow.. thanks for the support.  Let me look into it further taking into what you said.  Hate to have you use up your down time.  

 

 -Best,

Scott

[SteveJ]

What down time? I'll be at the convention.

[SteveJ]

Hello,

Thank you for your thoughts.  

 

Here is my problem... the dome and map light aren't working.  bulbs are good.  When I put a probe to the map light harness it tells me that one feed is connected to positive and one connected to negative , but I get no voltage.  For the dome light, the probe is telling me that all the wires are a negative feed.  that really shouldn't be that way.  

 

Any thoughts would be greatly appreciated.  

 

It's a late 260Z automatic.  

 

Doesn't everyone love electrical issues .

 

Thank you,

Scott

Okay, you say your bulbs are good. What about your fuse? These circuits share a fuse.

Next, use a multimeter to test electrical circuits. Using a probe to diagnose is like checking cylinder compression by putting your finger over the spark plug hole.   You can get a reasonable, cheap multimeter via Amazon or Harbor Freight.

 

If you had the map light in the on position when you were testing the dome light, you could have been backfeeding the map light. Since your back was to the map light, you wouldn't notice it, and it could fool you into thinking the red/blue wire was negative.

 

By the way, when you're checking what is in contact with ground using a multimeter, look at the resistance reading. Don't use the tone. A higher resistance reading could indicate you're backfeeding a circuit.

 

So, replace the fuse. It's cheap. Once you put in the new fuse, use your probe to see if it lights up when you touch either side of the fuse.

 

For more help, download the FSM from the link in my signature. The BE section does a nice job of breaking out the circuits. BE-18 and BE-20 have the circuits you're interested in.

[Kurbycar32]

First thing that comes to mind here is a bad ground.  The glove box light on my early 260z only has a power wire and is grounded to the bracket its mounted to.  This makes me think that your power circuit is good since the glove box light is at one of the ends of that circuit.  Steve gave you the correct advice but my suggestion is to change the fuse like Steve said then find all the grounding points and clean them.  If fixing your grounds doesn't fix the problem on its own it will assist you with diagnosis.  I detailed my experience here:

 

https://sites.google.com/a/thecomputerrehab.com/260z/electrical