Headlight wiring issue - Help!

[3rd_Gen_260Z]

Hi all,

 

I need some help deciphering a problem with my headlights. I'm not electronically minded and i'm learning on the go so i'm probably going to need you to explain this to me like I'm 5.

 

I'm trying to get my headlights working on my '75 260Z 2+2.

 

I started at the fuse box to see if there were any broken fuses, which there doesn't seem to be. My next thought was maybe it's something simple as the bulbs are blown. Before I start taking that apart I figured I'd make sure it's not an electrical problem with the wiring.  The rear lights work and licence plate light when I switch them on so it can't be a problem there. My parking lights work (LH only assuming bulb blown on the RH) and i've come to discover that high beam DOES work. However it only works on the RH side and upon checking the LH side its very dim, i can see its on but its not bright enough.

 

What could be going on here?

 

How does high beam and low beam work? Is it stupid to say there are two bulbs in the headlight?? If not what on earth is happening where by I can have high beam but not low? I'm starting to think its part of my overall electrical problem as other things don't work either.

 

Appreciate all assistance

[Linton]

the original light are sealed beam there are two elements in each light, and yes they can break (same as a house globe) but it would be unusual for all to stop working at the same time, you can test them just hook up a pos and neg wire straight to battery and touch the pins on the back, think the earth is the bottom pin but it wont matter you wont get zapped its only battery voltage.  check your fusible links and use a 12volt test light rather than a multi meter check your fuses again with the test light, lastly dim lights indicate an bad earth so check all your body earths

HTH

Linton

[Scoota G]

Check your fuses too as the old glass type can bust at the ends inside and look ok on visual inspection.

 

Mark

[Six_Shooter]

First rule of diagnosing electrical/electronics is:

 

"Thou Shalt check voltages"

 

Grab a DMM and measure the voltages at each point you have access to, including with the bulb(s) connected and disconnected from the circuit.

 

If you have full votage (around 12V) when teh bulbs are disconnected but low voltage when connected, this usually indicates a corroded wire or poor connection somewhere, that could also be caused by corrosion of the contacts.

 

remember the OEM headlight systems in the S30 switch the grounds, and the 12V is always live, so you need to source the ground from the circuit itself, not from the chassis or battery, when testing these circuits for voltage.

[3rd_Gen_260Z]

the original light are sealed beam there are two elements in each light, and yes they can break (same as a house globe) but it would be unusual for all to stop working at the same time, you can test them just hook up a pos and neg wire straight to battery and touch the pins on the back, think the earth is the bottom pin but it wont matter you wont get zapped its only battery voltage.  check your fusible links and use a 12volt test light rather than a multi meter check your fuses again with the test light, lastly dim lights indicate an bad earth so check all your body earths

HTH

Linton

 

Thanks!

 

It's been mentioned to me before that there may be an earthing problem with the car, I need to find those points and really look them over.

 

I knew the headlights were fully sealed, are semi sealed headlights easily accessible to buy?

[Scoota G]

Thanks!

 

It's been mentioned to me before that there may be an earthing problem with the car, I need to find those points and really look them over.

 

I knew the headlights were fully sealed, are semi sealed headlights easily accessible to buy?

Yes they are H4's. Search ebay.

[Zedman240®]

I would use a test light over a digital multimeter; they can give false readings...

 

Check the connections on your headlight switch..some do overheat and melt the solder holding the wires onto the switch itself.

[3rd_Gen_260Z]

I would use a test light over a digital multimeter; they can give false readings...

 

Check the connections on your headlight switch..some do overheat and melt the solder holding the wires onto the switch itself.

 

Test light seems to be the way to go. A friend from work has one he says i can borrow on Friday.

 

Going to check for any earthed wires tonight, I've also had a look on Ebay for some new H4 semi sealable lights (think i found some i like) to confirm if it's the bulbs.

[Six_Shooter]

I would use a test light over a digital multimeter; they can give false readings...

 

Check the connections on your headlight switch..some do overheat and melt the solder holding the wires onto the switch itself.

 

PLEASE PLEASE tell me how a DMM can possibly give false readings?

 

I have NEVER had a DMM do anything of the sort, and I've used dozens of different DMMs, in countless circuits.

 

I think what you mean is you don't understand how to use a DMM, so you use something that will not help you diagnose a problem, but give you pretty lights.

 

All a test light can do is tell you there there is or isn't power on a circuit, but not how much voltage (and/or current) is available.

 

To truly diagnose electrical/electronic circuits, you have to know that the voltage is not just there, but the correct amount, and at the correct times.

 

As I have already stated, a DMM can show that there might be voltage without a load (a test light IS a load), but then go away once a load is applied, this will tell you the type of failure you have (likely corrosion or carbon build up on a contact). If there is no voltage in both conditions this tells you that it's a different type of failure (likely a broken wire or bad fuse).

 

I'm not saying that a problem like this can't be diagnosed with a test light, but it will usually take longer than using a DMM, and knowing what to look for. I find that people that are afraid of DMMs, because they don't know how to use them, go to test lights and spend a lot longer diagnosing the problem than learning how to use a DMM on the same diagnosis.

[Zedman240®]

Just wondering how the OP went with the headlight issue... just had fun making a plug in relay system for mine as my switch kept melting and I found the reason why. Some @#$$ didn't wire one of the headlight plugs properly when it was changed so when high beam was applied, both high and low beams were on hence the dim light. Plus the wiring wasn't designed for a 120W globe so the headlight went dim. Now all the headlights work brilliantly and now I can drive at night with the high beams!

 

WIth DMM's, I'm not affraid of them I have around 3 different types and use them very often.. Ony time I use them on a car is to check chraging voltage..and that's about it. Many good autoelecs I have chatted to swear by the good oll testlight. When I was doing my emergency breakdown service job, test light was always in my hand with any electrical issue. Test lights can show you if there is any form of bad ground or low wattage...the globe wasn't bright! If you know how to use a tool properly, in the right hands its a very powerful diagnostic tool. DMM's have their place in electronics without a doubt... but when you are dealing with just 12V, test ligt for me works wonders.