Electrical assistance needed

[71GTX440]

Gents,

Here is the problem I am having on my 71 RR; dome light is constantly on.

1. Pulled door jamb switch (3 terminal) and cleaned contacts
2. Removed head lamp switch from dash and cleaned all connectors
3. Have power on circuit D31-188K coming out of fuse block to hazard flasher
4. Have power on circuit M1-18P coming out of hazard flasher
5. Have power on circuit M1A-18P coming off connection #5 with M1-18P
6. Have power on circuit M2-20Y coming off of connection with M1A-18P, heading to lamp switch behind dash
7. Have power coming out of lamp switch on circuit M28-20Y

I am thinking the internal circuit between M2-20Y and M28-20Y within the lamp switch is stuck closed, thus allowing constant power to feed the dome light.

Thoughts on this from anyone with a schematic that can check my work and assumption...

 

[Hemi 354]

Rethink this......I memory serves me correct, power is always there, it's a ground connection that the door switch sends to that light.

 

[Mopars & Missiles]

Well, don't have experience with a '71 but, on my '69's and my '70 the power to the dome light is always there. What turns the lamp on and off is the ground, it is switched on or off with the door jamb switch. So either your door jamb switch is defective and always is providing the ground, or you have a pinched wire somewhere between the jamb switch and the dome light that is grounded all the time.

 

[jimt1971rr]

I agree. The switch(s) create the ground to close the circuit and activate the light. I had a van what used to randomly flash the interior lights and it turned out to be a disconnected switch wire which was touching the body of the van and closing the circuit. Double check your wires for proper connection and breaks.

P.S. I have a 71 Plymouth FSM with wiring schematics. Both Body and Chassis manuals. If you need some specific pages scanned, P.M. me

 

[mopar 3 B]

May sound stupid but have you checked the tail lights.

 

[71GTX440]

Well, don't have experience with a '71 but, on my '69's and my '70 the power to the dome light is always there. What turns the lamp on and off is the ground, it is switched on or off with the door jamb switch. So either your door jamb switch is defective and always is providing the ground, or you have a pinched wire somewhere between the jamb switch and the dome light that is grounded all the time.

Sounds reasonable. Do you know what wire number I am looking for or where under the dash this ground is being picked up? The three wires running off the door jamb switch do not carry the typical green or white wire as a ground. 1 wire is yell, and 2 are orange. I am assuming 1 orange and 1 yellow wire go to the dome lamp and the remaining orange wire terminates at the M28-20Y and M2C-20Y junction

 

[71GTX440]

Rethink this......I memory serves me correct, power is always there, it's a ground connection that the door switch sends to that light.

I am willing to trace ground, another member suggested the ground.

I just pulled the three terminal jamb switch off the connection and still had constant power to the dome light. I should have no power as the connection would not be present without the switch providing the ground and power connection.

I may have to pull the kick panel off and cut off the electric tape to see if someone, somewhere hot wired a constant power wire to the butt connector for the dome light. Not sure of the point behind this, but it is plausible.

 

[jimt1971rr]

b
By looking at my FSM, the ground is on the Right door switch. Pull the other connector and see what it does. There are only two wires on the other door.

 

[Mopars & Missiles]

Sounds reasonable. Do you know what wire number I am looking for or where under the dash this ground is being picked up? The three wires running off the door jamb switch do not carry the typical green or white wire as a ground. 1 wire is yell, and 2 are orange. I am assuming 1 orange and 1 yellow wire go to the dome lamp and the remaining orange wire terminates at the M28-20Y and M2C-20Y junction

On my cars the body of the door jamb switch screws into the metal chassis of the car and provides the ground through the chassis. Freshly painted door jambs and/or switches prohibit a good ground and often cause people problems when they don't understand how this circuit works. There is no separate "ground" wire from under the dash, other than the wire from your headlight switch, which also provides a ground to turn on the dome lamp, IIRC. Your car may be wired differently, I suggest you get a FSM and learn how your car is wired.

 

[71GTX440]

b
By looking at my FSM, the ground is on the Right door switch. Pull the other connector and see what it does. There are only two wires on the other door.

Thank you! Looking at the schematics, they show the M28-20Y connection with M2C-20Y runs to the Right front door switch. Didn't think the ground could be pulled from the opposing door switch. Will see if that switch is bad.

 

[71GTX440]

On my cars the body of the door jamb switch screws into the metal chassis of the car and provides the ground through the chassis. Freshly painted door jambs and/or switches prohibit a good ground and often cause people problems when they don't understand how this circuit works. There is no separate "ground" wire from under the dash, other than the wire from your headlight switch, which also provides a ground to turn on the dome lamp, IIRC. Your car may be wired differently, I suggest you get a FSM and learn how your car is wired.

I have cleaned all the point from the switch and from the door jamb screw point. I am using the wiring schematics, I do not have a copy of the FSMs. I looked on mymopar for the FSM, but could not locate them. If you have a link to download the FSMs from that would be greatly appreciated.

 

[69BBody]

I may be wrong here, but wouldn't it be in either of these:
http://www.mymopar.com/downloads/servicemanuals/1971_Plymouth_Body_Service_Manual.zip
http://www.mymopar.com/downloads/servicemanuals/1971_Plymouth_Chassis_Service_Manual.zip

 

[71GTX440]

I may be wrong here, but wouldn't it be in either of these:
http://www.mymopar.com/downloads/servicemanuals/1971_Plymouth_Body_Service_Manual.zip
http://www.mymopar.com/downloads/servicemanuals/1971_Plymouth_Chassis_Service_Manual.zip

Perfect, thank you! When I was trolling around on MyMopar I could only find the wiring schematics. Thank you once again for these links!

 

[rrTor-Red]

Perfect, thank you! When I was trolling around on MyMopar I could only find the wiring schematics. Thank you once again for these links!

I was just going to post that. They're free and a god send.

 

[mopar 3 B]

May sound stupid but have you checked the tail lights.

Did not post this to sound stupid. Check the fuse to the tail light circuit. If blown it will allow the tail lights to ground the dome light.

 

[daytona71]

Just a thought, the instrument panel lights are dimmed by the headlight switch, turning fully opposite direction turns on the interior dome light. Could the dimmer portion of the headlight switch be stuck closed?

 

[71GTX440]

Did not post this to sound stupid. Check the fuse to the tail light circuit. If blown it will allow the tail lights to ground the dome light.

I have not checked the fuse for the tail light wiring, I will check it today. Thank you

 

[71GTX440]

Just a thought, the instrument panel lights are dimmed by the headlight switch, turning fully opposite direction turns on the interior dome light. Could the dimmer portion of the headlight switch be stuck closed?

I received a new head lamp switch yesterday from Rock Auto. Will be installing today. Waiting on a new two terminal switch to come in. Once done, will have all new switches, fuses and cleaned grounding points. Run continuity across all wires listed in the FSM under the dash and all were good, no breaks anywhere.

 

[71GTX440]

b
By looking at my FSM, the ground is on the Right door switch. Pull the other connector and see what it does. There are only two wires on the other door.

I pulled the right door switch, pretty corroded and rusty. I cleaned the two terminals with some 600 grit sand paper and cleaned up the door jamb hole. Light still stayed on, so I ordered a new two terminal switch.

 

[jimt1971rr]

I pulled the right door switch, pretty corroded and rusty. I cleaned the two terminals with some 600 grit sand paper and cleaned up the door jamb hole. Light still stayed on, so I ordered a new two terminal switch.

Did you do a continuity test of the swithch to verify it is bad?