Headlight issues 2

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Offline 1965 fastback

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Headlight issues 2
« on: March 17, 2023, 10:27:01 pm »
To continue the thread of headlight issues, I have a photo attached of the plug which attached to the light switch on a 65 Mustang.

The three circles areas are confirmed as having power to them but the rest did not light up.

For context, neither my low beam or high beam work at the moment but park lights, brake lights, indicators and a couple of dash lights work.

The light switch is new. Replaced when I could only get high beam not low beam about a year ago. New switch did not change anything. Checked wires all the way through and could not find anything loose or cut. The earth for the lights seem in tact and well grounded.

My question is does the fact that the plug to the light switch only having three connections with power to them indicate a problem or is that normal? I would have thought other connections would be made/powered when the switch control is pulled or turned?

Am trying to work through these issues one at a time.

I can’t discount the new light switch being a dud.

I also note that when I pulled the plug holding all the lighting cables from the firewall under the bonnet near the brake master cylinder, this disconnected power at the ignition, which may be normal but seemed odd.

I also tried checking power to the headlight plug and got nothing with ignition on.

If anyone can help diagnose this or point in the right direction, it would be much appreciated.

I have included the switch with the terminals that have power going to them.

Tony
« Last Edit: March 17, 2023, 10:30:40 pm by 1965 fastback »

Offline GEOFF289

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Re: Headlight issues 2
« Reply #1 on: March 18, 2023, 12:53:28 pm »
This might help

https://stangnet.com/mustang-forums/attachments/hlswitch-jpg.220886/

Pulling the plug from the firewall will disconnect everything, including ignition. What your pics seem to show is power coming in from the battery OK and going to the courtesy light switch and fuse. I think this is what I'd expect with the plug disconnected from the switch as I think the power comes into the switch and straight out to the courtesy light switch. The other terminals will only have power when the switch is plugged in and activated, or the brake light switch is activated.

So if I'm right about this, and again don't mistake me for an expert, this test doesn't really tell us anything. Did you test the headlight plug the sealed beam unit plugs into with the lights switched on? Obviously there'll be no power there is it's not switched on.
« Last Edit: March 18, 2023, 01:25:07 pm by GEOFF289 »

Offline 1965 fastback

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Re: Headlight issues 2
« Reply #2 on: March 18, 2023, 01:31:47 pm »
Thanks Geoff. Does that suggest to you power is not getting to any other part of the light switch?
Should I be expecting more of those connections to light up? This would also indicate the switch is not the problem…
I assume adding a relay won’t remedy the problem either.

Offline GEOFF289

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Re: Headlight issues 2
« Reply #3 on: March 18, 2023, 05:47:11 pm »
Hope we're not talking at cross purposes.

With the switch and plug separated there'll obviously be nothing happening at the switch. The plug will only have the main feed from the battery going in and it makes sense that it will have the power going out to the courtesy lights. This appears to be what you found at the plug.

To test further you'd need to connect the switch and plug with the switch out of the dash and probe for power on the back side of the plug where the wires enter the plug. I don't know off hand if this is physically possible.

What I've been suggesting is to test for power at the actual light socket where it plugs into the sealed beam unit, with the light switch on obviously. If you have power there the fault must be either the sealed beams units themselves or earthing. If you don't have power there your problem is upstream towards the switch.

You could start by unplugging the firewall connection and testing for power at the appropriate posts on the firewall. You'd have to consult Dr. Google as to which post on the firewall fixture should have power with the headlight switch on, I don't have a diagram of this. If you have no power there the problem is inside the car. If you do have power its under the bonnet.

I think its relatively unlikely its the new switch itself as you have parkers and brake lights and the new one didn't change anything from the old one. I still reckon an earthing issue is most likely.

Where in Melbourne are you?

Offline AussiePhil

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Re: Headlight issues 2
« Reply #4 on: March 18, 2023, 05:56:00 pm »
Hey Tony,
I’ve read your posts, certainly have a problem.

The relay I bought was from eBay.
It is very good quality as far as I’m concerned.
And it’s easy to fit, all you need to do is add a 12v supply and earth and the plugs plug directly into the light plugs.
I would have used a NEW ERA relay but I’ve moved my wiring out of the way in the engine bay and it was easier that way!

It was something like this one; you only need one for single high / low beam lights on our early Mustangs.

It’s just two normal relays wired together properly and harness to suit.

Not sure this is your problem but it can’t hurt!

Cheers Phil.

These have the ceramic plugs for heat and are much cheaper than others sell.

https://www.ebay.com.au/itm/224560670633

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Offline GEOFF289

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Re: Headlight issues 2
« Reply #5 on: March 18, 2023, 06:50:43 pm »
Phil is right, a quality relay kit is a good idea. I don't think the absence of one is your problem though.

Offline 1965 fastback

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Re: Headlight issues 2
« Reply #6 on: March 18, 2023, 11:39:28 pm »
Hope we're not talking at cross purposes.

With the switch and plug separated there'll obviously be nothing happening at the switch. The plug will only have the main feed from the battery going in and it makes sense that it will have the power going out to the courtesy lights. This appears to be what you found at the plug.

To test further you'd need to connect the switch and plug with the switch out of the dash and probe for power on the back side of the plug where the wires enter the plug. I don't know off hand if this is physically possible.

What I've been suggesting is to test for power at the actual light socket where it plugs into the sealed beam unit, with the light switch on obviously. If you have power there the fault must be either the sealed beams units themselves or earthing. If you don't have power there your problem is upstream towards the switch.

You could start by unplugging the firewall connection and testing for power at the appropriate posts on the firewall. You'd have to consult Dr. Google as to which post on the firewall fixture should have power with the headlight switch on, I don't have a diagram of this. If you have no power there the problem is inside the car. If you do have power its under the bonnet.

I think its relatively unlikely its the new switch itself as you have parkers and brake lights and the new one didn't change anything from the old one. I still reckon an earthing issue is most likely.

Where in Melbourne are you?

I’m in Ringwood Geoff.

In answer to your comment above, I tried taking out the headlight and testing the plug behind with ignition on but found no power to the plug.

If I connect the lighting plug to the switch under the dash there is no way to test which connection has power hence separating the switch to gain access to the connectors.

I disconnected the lighting cable plug at the firewall which shuts down ignition and found no power at any of the posts there either. This didn’t surprise me because if separating that plug shuts off the ignition I can’t see how any power would be present because there isn’t a complete circuit.

I agree it must be an earth somewhere and I read on one site that an earth should run from the frame holding the instrument cluster to the same place where an engine strap is earthed?? That I had not heard before which begs the question should there be an earth behind the instrument cluster that I am missing or is faulty… and could this faulty earth cause both headlights to fail?

I also agree I don’t think it is a lack of a relay in my case but I do want to upgrade the headlights at some point if I can get the existing ones to work so thanks Phil for the tip on the cable extension and relays, I will give those a go.

Tony

Offline 1965 fastback

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Re: Headlight issues 2
« Reply #7 on: March 18, 2023, 11:40:54 pm »
Hey Tony,
I’ve read your posts, certainly have a problem.

The relay I bought was from eBay.
It is very good quality as far as I’m concerned.
And it’s easy to fit, all you need to do is add a 12v supply and earth and the plugs plug directly into the light plugs.
I would have used a NEW ERA relay but I’ve moved my wiring out of the way in the engine bay and it was easier that way!

It was something like this one; you only need one for single high / low beam lights on our early Mustangs.

It’s just two normal relays wired together properly and harness to suit.

Not sure this is your problem but it can’t hurt!

Cheers Phil.

These have the ceramic plugs for heat and are much cheaper than others sell.

https://www.ebay.com.au/itm/224560670633

Thanks Phil, I will give those a go once I sought out my current electrical issues. I want to update the headlights since I drive it regularly.

Tony

Online peter9231

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Re: Headlight issues 2
« Reply #8 on: March 19, 2023, 12:45:01 am »
Dip switch
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Offline GEOFF289

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Re: Headlight issues 2
« Reply #9 on: March 19, 2023, 09:07:07 am »
Well that was a brain fade on my part. Of course what I suggested about testing for power at the firewall plug was dumb. I blame a full day of wrangling a couple of grandchildren. In theory you could rig up a power feed direct from the battery to the appropriate pole on that plug and then see if you have power at the headlight poles (high and low beam) on the plug. As long as you have this connection apart, wouldn't hurt to spray some electrical contact cleaner on both parts and ensure its all gunk free. E.g.

https://www.supercheapauto.com.au/p/sca-sca-electrical-contact-parts-cleaner-350g/347119.html

Just in re Peter's point about the dipswitch - you've already tested and found power there haven't you? If you have power at the dipswitch it confirms the headlight switch isn't the issue and the problem is between the DS and the light. Given that you found no power at the light plug and both lights are affected that further narrows it down. One of the three poles on the light plug is earth, don't know which one. Have you traced that back to the point where its supposed to earth and verified that its a good earth connection?

While I would never rule out anything with the electrics of these old girls I doubt that the earthing of the dashboard frame is your issue. Your dash lights and gauges work don't they? As a possible separate issue, you do have a good earth strap from the LH back of the block or head to the firewall?
« Last Edit: March 19, 2023, 09:49:26 am by GEOFF289 »

Offline 1965 fastback

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Re: Headlight issues 2
« Reply #10 on: March 19, 2023, 12:29:07 pm »
Thanks Geoff. Appreciate your perseverance on this (and everyone else of course.

I haven’t tried to see if there is power to the dip switch yet, so that will be next.

I did note all the poles in the firewall plug were in pretty good nick, both sides but worth adding the lube for good measure.

I am also going to pull the earth wires for the headlights and give them a scrub.

As for block earth strap, yes I have a good one installed when I swapped in the new motor.

As for dash lights, while some work, some don’t. When I start the car, the speedo light glows but if I pull the light switch for park lights or headlights it goes out… maybe an earth problem there too.

Strange that all these things worked for ages and now don’t. I guess they have to break down sometime. The car was getting a fair bit of daily work for awhile.


Offline 1965 fastback

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Re: Headlight issues 2
« Reply #11 on: March 26, 2023, 10:05:26 pm »
Just to update the group on my headlight issues…

I have tried the following suggestions:
- disconnected the headlight firewall plug and wired power directly from the battery to the plug, low and high beam worked. This tells me the obvious that the bulbs are fine and earthed.

- I discovered the earth for the dash cable was also earthed properly.

- cleaned the plug and prongs in the dipswitch and while pushing that switch with ignition on the headlights flashed on momentarily and then turned off. This suggests the dipswitch could be the fault however the mechanism itself seemed to
Click properly. Has anyone had their dipswitch fail? I assume these are easy to purchase?

- I could also have a faulty headlight switch, even though it is relatively new. Has anyone had this issue of replacing the light switch and have it fail? Are there cheap switches I should avoid?

Please share your similar experiences.

Tony

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Re: Headlight issues 2
« Reply #12 on: March 27, 2023, 02:44:28 am »
Dip switch
"If you are not prepared to be part of the solution you forfeit your right to criticise"

Offline 289 vert

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Re: Headlight issues 2
« Reply #13 on: March 28, 2023, 11:04:23 pm »
^^^ What he said ... twice.
Center pin on the dipswitch plug is power, outside pins are hi and low. Look for power there.
If power there, make a temp jumper between the center and an outside pin to bypass the switch.
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Offline 1965 fastback

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Re: Headlight issues 2
« Reply #14 on: March 30, 2023, 07:17:44 pm »
It was the dipswitch! Low and high beam work.

Thanks everyone for your help. Peter is owed a beer.