TwinTurbo.NET: Nissan 300ZX forum - Re: High beams and no low beams,dash light or tail lights
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Subject Re: High beams and no low beams,dash light or tail lights
     
Posted by compirate on January 24, 2018 at 8:54 PM
  This message has been viewed 343 times.
     
In Reply To High beams and no low beams,dash light or tail lights posted by Lowlife1998 on January 24, 2018 at 07:20 PM
     
Message I had this problem, which magically went away by itself, so I have no idea why it did what it did, but here's how the system works and what to check easiest first.

The system is wired as follows, one to the next:

1. Battery
2. Fuse #3 10A (interior fuse panel, top row, 3rd from the left)
3. Light switch
4. Left pin of dimmer relay coil (see attached picture)(Black relay in relay box under hood)
5. Right pin of dimmer relay coil
6. Dimmer switch
7. Body ground

When the relay is off - ground for hi beams.
When the relay is on - ground for low beams.

The first obvious thing is to check Fuse #3, which people have said still checks good, but if replaced with an OEM quality one usually fixes the problem. Fuse #3 also powers the clearance, tail (not stop or brake) and instrument illumination.

The dimmer switch (high beam switch) has three positions A - high beams, B - low beams, C - Flash lights

Next, have someone turn the light switch on, dimmer switch in position 'B' and see if dimmer relay clicks. Put your finger on it, you should feel it do so. This will let you know if power gets here at least. If no, remove relay and check for 12v on lower left pin in the relay box (see attached picture). Check for ground on lower right pin. If yes it clicks, check that it's still good by removing it and put 12v on the two bottom pins and check for continuity on the top center pins and the top and top right pin. On - top center connected, off - top and right top connected. If all is good, I'm stumped.....

If your fuse is good, but you don't have power here, go to the light switch next. If you have power, but no ground, go to the dimmer switch.

Light Switch
Remove the light switch and then the bottom connector. Looking at the end of the connector, pin 5 is the top row, second from the left. Should be 12v (comes straight from battery through fuse #3). If yes, then with the switch on all the way, check continuity on pins 5, 6 and 7 on the switch. They're the 2 on the right, top and bottom and the top second from the right.

Dimmer Switch
I'm not sure how hard the dimmer switch is to get to, but if you can remove that connector (it's the biggest one there), with light switch on, check pin 44 - there's 2 pins vertical, should be the left side, it's the top one - for 12v. Check the bottom one for ground. Check the reciprocal pins on the switch for continuity.

Only thing left are the body ground connections, one is in the left side foot-well, the other is on the right side foot-well.

     
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