78 NYB Radio goes off when I hit the brakes.

[73 T&C]

Something new on the shakedown today...

Hit the brakes and the radio went off and the map light went on... go figure.

Brake light circuit (7) had blown fuse.

Changed the fuse and now no radio and no Brake Lights.

Anyone out there have any ideas???

 

[Carmine]

Map/courtesy lights are on the same fuse as brake lights. Something is grounding the map lights when you apply the brake. I'm thinking:

1) any old trailer harnesses?

2) broken and shorted brake lamp filament?

Wiring diagram invaluable here.

 

[73 T&C]

Replaced the 20A fuse for circuit 7 (bad fuse) after finding and wiggling all the tail light plugs.

Radio working independent of brake now and brake lights working again

 

[1970FuryConv]

Hit the brakes and the radio went off and the map light went on... go figure.
Brake light circuit (7) had blown fuse.
Changed the fuse and now no radio and no Brake Lights.
Anyone out there have any ideas???

Hi Javier. That's no fun.
*According to my 1973 wiring diagram, the Chrysler map light and brake light are on the same fuse. The radio is on a different fuse. If 1978 is same, then:
*If the brake light/map light fuse blew, the map light had to be getting power from somewhere in order to come on.
*My guess is a short between the map light and radio wiring. You hit the brakes, wires shift position slightly, short occurs, maps light takes radio power. Map light comes on, radio goes off. Another shift of position due to braking, accelerating, cornering, or wiggling of wires and intermittent short goes away.
*20 amp fuse will last until wires shift again and short reappears
*I'd be looking for continuity between the wire connector at the back of the radio and the wire connector for the brake light switch. Once I had my ohmmeter hooked up, I'd wiggle wires and see if continuity appeared. It helps to have an assistant watch the ohmmeter while you're wiggling wires.
*Not sure if your car has rear speakers, but if it does, I'd look for a place of wear, like the edge of a sill plate, and look for a short below. Also, any place where there might be water damage is a likely spot. Best of luck!

 

[cantflip]

Wiggle wires if you like... check for bulbs out (Carmine's short) then quit thinking about it and toss a few spare fuses in the glove box.

Fuses fail... period. Without a second occurrence, it's not worth trying to figure out.

BTW... whenever weird stuff happens like that, you've either lost power or ground... fuses are the best (easiest) place to start.

 

[1978 NYB]

Check and see if the antenna cable is plugged in tight.

 

[73 T&C]

Check and see if the antenna cable is plugged in tight.

Funny.... Bob!

 

[cantflip]

Check and see if the antenna cable is plugged in tight.

Yep ... just reach in and give it a wiggle...

 

[73 T&C]

 

[detmatt]

Probably the wiper cam.

 

[78Brougham]

Or the thermostat...

 

[commando1]

Or the thermostat...

Nope. It's not the thermostat. All the wires going to the thermostat are fine.

 

[Big_John]

Nope. It's not the thermostat. All the wires going to the thermostat are fine.

Then it's the ballast resistor.

 

[78Brougham]

Starter...

When I was a kid working in the garage on something that wouldn't start, my "Gramps" (God Bless his soul) would name every conceivable part on the car that would cause a no-start situation. Then when I got it running he'd say "Told Ya that's what it was"

God I miss him.

 

[73 T&C]

My money is on the rear view mirror......

Seriously.... drove it all morning with no issues.

Radio and Brakelights all working independently.

Took Jeff’s advice and put a box of fuses in the glove box. Cheap insurance.

Car seems to be running better every time I drive it. Also, tweaking the idle and mix on the carb as I go. These lean burners are very sensitive to mix and temp.

 

[commando1]

Also, tweaking the idle and mix on the carb as I go. These lean burners are very sensitive to mix and temp.

Still???

 

[73 T&C]

Still???

Yep. Between initial start (smooth) and up to temp (smooth), idle is a little low and a little unstable.

I need to check the wiring for the thermostat......

FSM calls for 195 degree thermostat. Recall notice calls for 180 degree.

She’s slow to warm up...... and it’s summer.

 

[commando1]

I need to check the wiring for the thermostat......

 

[73 T&C]

Fuse blown again....

Found my problem....

Brake light circuit wires were run around the very top of the brake pedal for some reason. Had worn through the insulation and was grounding out the circuit and blowing the fuse.

Maybe what is causing the cruise not to work.

Why they wrapped the wires around the pedal, I’ll never know. I pulled it loose and put some tape around it to hold it but I need to go in and properly sort it.

One thing for sure... this car has the unfriendliest, tightest, most crowded under dash area I’ve ever worked on....

 

[78Brougham]

You wouldn't be saying that if you've ever been under the dash of an Esprit.