OK, Here is what has been replaced, and the problem on my 1975

Complete engine bay wiring (forward lamp and engine harness) and installed new led lights in dash and rear lights and side markers. Installed new led flashers with grounds. Insured all grounds were in correctly and tight. Installed new Turn signal switch. 4 ways work perfect. Brake lights work perfect and back up lights and tail lights.

Problem - no front side marker lights. With led bulbs installed they are very dime and don't flash anywhere. Normal bulbs don't light up at all. With normal lights installed and led rear lights my signal lights on the dash come on with the head lights. They don't with the led bulbs installed.

I'm so confused,help please!

 

I suspect that your mix of LED and incandescent lamps is to blame. The front turn/park lamps and front side marker lamps operate in an odd "push-pull" fashion whereas one is on while the other is off.

I know that LED lamps are all the rage but they cause obnoxious problems in circuits that weren't designed for them.

Have you cleaned/inspected the rear lamp harness ground near the radio antenna?

 

DUB

 

Ya I am going to put things back to normal tomorrow and see if that works.

 

Also voltage reading instead of dim at marker light would help

 

The side markers are connected between the running light power wire and the turn signal power wire. This causes them to come on when either the running lights or signal lights are lit, but turn off when both the signal and running lights are lit. It was a cheap way to use a single filament bulb and have it do both running and turn signal duty. The circuit relies on the different filament resistance in the little marker light, the turn signal filament and the other marker light filaments all in parallel. As soon as you install LED's, you completely upset the resistance and it quits working right.


You either have to;
- add a load resistor to each front signal light and the running light circuit.
- add relays to isolate the marker light from the signal light.
- wire the marker lights to be grounded so they only come on with the running lights and don't flash with the signals.
- wire the marker lights to be grounded so they only come on with the signals but don't come on with the running lights.
- keep using normal bulbs in the front of the car, maybe rear too.

I'm not a fan of resistors, they tend to get hot and fail at the connections, melt things or burn out a lot, especially if they are connected to power all the time. But, they would fix this. I wouldn't go for 30W resistors. Try a 10W body size running maybe 3W or so. Somewhere around 50-65 ohms.

Relays would work and not burn-out or melt anything, but I can't picture a circuit that would work and give the same functionality without using 2 relays.

The other options, well they fix it but are probably not what you want.

 

I put the normal bulbs back in, changed flashers and everything works again. Not worth the head ache to have leds in my opinion now.

 

I think that's a good idea. Beyond the fact that the circuits weren't designed for LEDs, neither were the fixtures. The DOT (Department of Transportation) have extremely finicky requirements for beam spread, color, intensity, etc. of most of the external lighting in vehicles. Those requirements effectively demand that the lighting fixture be designed for use with a very specific lamp.

I too dislike the use of power (>5W) resistors outside of enclosures designed to contain any damage caused by the heat they generate in both normal and problem (like over voltage) situations.