Possible head light switch problem

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vintageman

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Ok, so I have a 73 Mach 1, engine harness, dash harness, and rear harness reconditioned and checked by Midlife, so I am good there. I have recently installed all of the harnesses, pulled dash and reinstalled harness, replaced the headlight switch, ignition switch, turn signal switch. I also have the updated cluster harness from Midlife that hardwires the lights. My problem is this, with headlight switch turned off, my turn signals work in the rear and on the on the front grill (BTW, I have a 71-72 grill with the amber lights). When I switch my headlights on, I get turn signals in the rear but not on the front grill. The 4 way hazard flashers are the same, front and back work with headlights off and just the rear when the headlights are on. I am thinking the new headlight switch may be the problem. I did purchase it at cjpony.com and I have had issues with their products before.  What are your thoughts, any help is appreciated. 

Tom

 

midlife

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71/72 grill doesn't have turn signals in the sportslamps, but in the lower valence parking lamps.  If this is a 73 with 73 front lamp wiring, the turn signals should be in the grill lamps.  Are you using the right bulbs?  You'll need the two filament bulbs for 73 grill lamps. 

My notes for your build has the headlight harness being entirely 1973, with no grill lamps and 72 parking lamps/turn signals in the lower valence. 

I may have mis-interpreted what you wanted or my spreadsheet notes were incorrect.  e-mail me and let's get this straightened out.

 

vintageman

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Thanks Randy, your notes are correct, I do have a 73 harness. When you did the work on my headlight harness, I had a 73 grill but later decided that I wanted to change the grill to a 71-72 style. I have the 1157A bulbs in the grill now, are they the correct bulbs?  Thanks for your assistance on this.

Tom

 

midlife

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1157's should be the correct bulb.  Sounds like the grill lamps aren't grounded.  Can you pull the bulb and socket and check continuity from the prong on the side inside the socket to chassis?

 

vintageman

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Thanks Randy, I will check that tomorrow night when I get off of work, tied up tonight so now work on the Mustang. More to follow. 

Tom

 

vintageman

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Thanks again Randy for your response and expertise on this. I did a continuity check from the plug to the chassis and came up with a high number (200+). I have checked the headlight harness grounds and they are metal to metal good grounds. I have an extra new headlight switch to check but wanted your thoughts before. Thanks?

Tom

 

Don C

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Whenever I check for grounds I check the ground continuity from the item (light socket, motor, etc.) to the negative post on the battery.

 

midlife

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Whenever I check for grounds I check the ground continuity from the item (light socket, motor, etc.) to the negative post on the battery.
Before Tom buys a new headlight switch, if the ring connectors on the headlight fasten into newly painted metal, then they may not make good contact.  You need to use toothed ring connectors and scuff the paint to ensure good continuity.

 

vintageman

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Thanks Don and Randy for you responses, I did take the paint down to bare metal to test the grounds. I inserted the multimeter into the light plug at the pin and tested for ground. The results were the numbers I posted above. Tomorrow I plan to cut one of the ground wires from the plug and retest the ground. If good, then I may have bad plugs but I doubt both are bad. I do full expect it to be the headlight switch because both turn signals do not work with the headlights on and the turn signals work without the headlights on. I already have a new headlight switch, but it is the same part brand from the local auto-parts store. More to follow tomorrow night. 

Tom

 

Don C

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Before Tom buys a new headlight switch, if the ring connectors on the headlight fasten into newly painted metal, then they may not make good contact.  You need to use toothed ring connectors and scuff the paint to ensure good continuity.
+1 on the toothed rings. If not available, toothed lock washers between the ring and the body work nearly as good. I've found that the toothed lock washers with the teeth on the inside of the washer are better than the ones with the teeth on the outside. The connectors with the built-in teeth are better, just not as easy to find.

 

midlife

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The reason why your turn signals work without headlights on is that the ground for the turn signals is using the running lights on the second filament as a pseudo ground path.  This is how the awful 1970 system works: no true ground.  I doubt that the headlight switch change will make any difference.

 

vintageman

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That is a great explanation for the turn signals working when the headlights are off Randy, thank you for the education, I appreciate it. I looked around at a few local auto parts stores this morning and had to buy some star washers instead. I will try to get to it again later tonight and report back. Thanks again.

Tom

 

vintageman

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I forgot to let everyone know that I did get this issue fixed. I cleaned up the painted surface some more for the grounds and used star washers to ensure good contact. I still had the same issue, and replaced one of the bulb sockets and it worked, so I replaced the other and everything worked well afterwards. Thanks for everyone's advice and expertise on this, one more thing complete and closer to getting this one back on the road.

Tom
 

Don C

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Good job. Don't worry, more gremlins will pop up to test your mettle.:giggle:
 

vintageman

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Thanks Don, I appreciate it and will always be on the lookout for these pesky gremlins.

Tom
 

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The reason why your turn signals work without headlights on is that the ground for the turn signals is using the running lights on the second filament as a pseudo ground path. This is how the awful 1970 system works: no true ground. I doubt that the headlight switch change will make any difference.
I second that comment on the one year only 1970 parking and turn signal wiring.. what a mess!

Sorry, I am a bit late to the party, but it may help someone else....Since you have a 73 harness designed for three-wire Parking/Turn signal bulbs in the grill. I think but not 100% positive, that the 1973 Mustang three-wire Parking/Turn signal bulb fixtures will fit the 1971-72 grill and will convert those 72 grill lights to support both parking and the turn signals with the correct two filaments 1157A bulb.

Look for a S-519 Bulb Socket Front New for Truck F150 F250 F350 Mustang Ford F-150 F-250 II or a 85898 Dorman Bulb Socket Front New for Truck F150 F250 F350 Ford F-150 F-250. I forget which one I used to replace a socket on my 73.
 
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vintageman

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I second that comment on the one year only 1970 parking and turn signal wiring.. what a mess!

Sorry, I am a bit late to the party, but it may help someone else....Since you have a 73 harness designed for three-wire Parking/Turn signal bulbs in the grill. I think but not 100% positive, that the 1973 Mustang three-wire Parking/Turn signal bulb fixtures will fit the 1971-72 grill and will convert those 72 grill lights to support both parking and the turn signals with the correct two filaments 1157A bulb.

Look for a S-519 Bulb Socket Front New for Truck F150 F250 F350 Mustang Ford F-150 F-250 II or a 85898 Dorman Bulb Socket Front New for Truck F150 F250 F350 Ford F-150 F-250. I forget which one I used to replace a socket on my 73.
Thanks Rich, I got them working now. The running lights in the 72 grill work and they also work as turn signals.

Tom
 
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