70 Mach 1 Hood Scoop Light Question

[rutkak 0]

Hi Folks,

  Are the hood scoop lights on a 70 Mach 1 supposed to light up dimly when the running lights and lights are on?  Mine do but they function normally with turn signals or hazards.  I ask because I have a 69 Torino GT and they only light up fully when the turn signals or hazards lights are on.  On the Torino they are completely off when the lights are off unless I use turn signals or hazards. 

  On my 70 Mach 1: the grounds are good, the bulbs are good and the wiring harness from the bulbs to the plug above the brake booster is good.  I swapped in my 69 Torino top wiring harness with bulbs to the plug by the booster with the same results.  The wiring harness after the plug is different on the cars:  4 on the 70 vs 2 on the 69.  Certainly they are different cars but I have fog lights on the Mach 1 so I'm sure that's part of it. 

  Before I chase down the plugs can someone verify I'm not chasing something that is normal.  I'm good with wiring but I personally converted to EStreet EFI w/sump and dizzy, dual electric fans, have a headlight relay so it's pretty tight in there with wires and I loomed most things together. 

Ken

[Tnstratofam 2]

The hood scoop lights on our 70 only come on when the turn signals are on. Either with the left or right turn signals or emergency blinkers active. They are not on otherwise. Our Mach 1 is Original and been in the same family ( Dad bought new and gave it to me ) since 1969.

[det0326 179]

I know you said your grounds are good but that is a a sign of a bad ground not on your scoop turn signals but something else grounding through them such as light in ignition switch, one of your park lights, or any other light that should be on at the time the scoop lights are on dimly.    A bad ground will cause weird things that you would not suspect.  

[rutkak 0]

Thanks guys.  Now I know to start looking deeper.  I've checked every ground on the car several times and found a few gremlins which fixed other stuff.  I'll have to start looking again.  The other possibility running through my head is that perhaps a LED light or two in the system aren't providing enough resistance.  I only have a few LEDs (side markers and fog lamp) so that should be easy to rule out by swapping back in normal bulbs but then again my Dakota Dash is also on that circuit...ehhh, I'll figure it out.  Thanks again folks.

Ken

[RPM 1,190]

6 hours ago, Tnstratofam said:

The hood scoop lights on our 70 only come on when the turn signals are on. Either with the left or right turn signals or emergency blinkers active. They are not on otherwise. Our Mach 1 is Original and been in the same family ( Dad bought new and gave it to me ) since 1969.

Welcome to the forum! It's pretty special and rare these days to have a 48 year old car still in the same family. I'm sure others beside myself would love to hear the story of your Mach 1.

[LiLMike 42]

+1 On the grounds. Don't ground a lot of things to one point either. I had grounding issues and that was the problem. i used multiple ground points, moved ground wires to different points and grounded the enging block in 3 different places. I'm good to go now.

[danno 128]

I know exactly what the problem is.   This one is easy.  The front parking/ turn   combination lights under the front  bumper are not grounded.  This happens a lot. Disconnect the harness going to the left and another harness on the  right combination light, there should be a connector under the front of the radiator to each.   Disconnect these and I will bet you a beer the problem will go away. 

  Then it is a matter of figuring out the ground issue.  It seems to me there is a pigtail wire from the combination light socket that gets put under a mounting screw, but I have a 69 and I know they are different for 70.   That is the issue.

[rutkak 0]

Danno, I'll check it out and easily buy you a beer if that's the case.  More to follow. 

Ken

[rutkak 0]

Danno, I disconnected the front parking lights with no change.  I'm about 95% confident all of the grounds are good to go, did a resistance and voltage drop test.  I didn't check with normal (non LED) bulbs in, but I only have those on the side markers. 

Ken

[danno 128]

OK, now I understand a bit more.  The connections for the hood scoop lights is (as you said) a 4 wire connector for a 70.  That changes things.  It also changes things because I think the front parking/turn lights are wired different on a 69 and 70.  What you need to disconnect is the front combo turn signal/parking light, not the front side marker light. I am not sure you can disconnect them in a 70.  What you can also do is remove the front combo bulb on both the left and right side.

There is another easy thing to try that could indicate where the problem is.  This only works if you have an old style flasher.  If you have an electronic flasher installed, it will not work.  But what you need to try is to turn on your left turn signal.  Take a note of the speed it is flashing.  Then turn on your parking lights, and see if the speed of flashing changes.  Do the same with the right turn signal.  If you have a factory style flasher, and the speed of flashing changes with parking lights on, this could be a clue.

One other question... did this 70 Mach work correctly at one time, and now it is not?  Or has it always worked incorrectly like this?

[rutkak 0]

Danno,

  Thanks for the reply.  In short, the hood scoop lights have lit up dimly since I bought the car a year ago, as far as I can remember.  She needed a decent amount of work to be road trust worthy so I generally didn't drive her at night much though but it's been that way since I started modifying things.  The blinkers are the same speed, although I have electronic sequentials in the back and modern flashers. 

  On the 70s you can disconnect the front parking light / turn signal pretty easily and I did with no change.  I also pulled the side marker front bulbs with no change. 

  My next step, this weekend is to systematically pull or disconnect every bulb and see where there is a change. 

  Thanks again,

Ken

 

[danno 128]

Oh.... now I have another idea.  It could be that the electronic  sequentials in the back are doing it. Reconnect all front lights, and pull the plug going ot all rear lights.  There are 2 connectors just to the left side of the ampmeter, and above the left side A/C vent.  If you disconnect those, it shuts off all electricity to the rear.

[rutkak 0]

Figured it out.  It ended up being the front LED parking lights.  Perhaps it wasn't giving enough resistance.  Interestingly, the front parking lights ground through the housing connection screwed into the bumper.  I started disconnecting all the bulbs in the back then unscrewed the front parking lights and noticed the ground is the bumper.  I cleaned up the connection with a Dremel wire wheel.  No change, but then I swapped back in a normal bulb and the hood scoops are good to go. 

  In total, I'm running LEDs on all of the side markers (front and back) and on the sport lamps (Mach 1) without issue.   

Thanks Danno and all those that replied. 

Ken