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| dome light https://slantsix.org/forum/viewtopic.php?t=61946 |
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| Author: | '67 Dart 270 [ Sat Feb 10, 2018 7:23 pm ] |
| Post subject: | dome light |
My dome light is on, very low power level, when my car is at rest. Since the dome light circuit works on a ground, i.e. when the door is open, the switch grounds and current flows, I assume that there is a short somewhere and some small amount of current is flowing. It is an LED bulb, very low draw, so the short/ground isn't much. When I turn the key to acc or run, the dome light goes off. NOTE: I recently installed Sebring seats and part of that was wiring into the door switches' wiring. I did observe during this process that the wires going to the door switches were twisted pretty badly. So, my assumption is that there is either a short in one of the door switch wires (from the extensive twisting) OR the Sebring seat circuit has a low level ground. If it were a full ground, the dome light would be on at full strength. Q: has anyone had a door switch wire slightly short/ground and make their dome light be on at a low level like this? Brian |
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| Author: | '67 Dart 270 [ Sat Feb 10, 2018 7:25 pm ] |
| Post subject: | Re: dome light |
Second note: I was very careful to make sure all my connections were good and all connections were well insulated/protected. |
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| Author: | Pierre [ Sat Feb 10, 2018 10:39 pm ] |
| Post subject: | Re: dome light |
It may not be a short due to physical issues (frayed etc) Can you unplug the wiring to the seats and see what happens? I'm not sure how the sebring seats wire up, but it sounds like you made another path to ground through the seat electronics. So imagine the switch in the open position (not shorted to ground). Dome light goes to the switch. If you tapped into this wire, and this tap provides another path to ground (through some other resistance), you'll get some fraction of current flow. Hence why the light comes on, but dim. You may need to tap into another wire on the switch, or use an appropriate diode to isolate. |
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| Author: | '67 Dart 270 [ Sat Feb 10, 2018 11:10 pm ] |
| Post subject: | Re: dome light |
Thanks Pierre, I'll unplug the seats and see what happens, good idea. That's what I was saying, either the door switches or the seats, I don't think it's my wire job/connections. I'll report back. B |
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| Author: | Dart270 [ Sun Feb 11, 2018 5:26 am ] |
| Post subject: | Re: dome light |
Door switches can also have a weak ground path and cause dim light, I have heard. Lou |
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| Author: | DusterIdiot [ Sun Feb 11, 2018 8:31 am ] |
| Post subject: | Re: dome light |
Don't forget that the late A-bodies also light the dome light as a convenience if the light switch rheostat is turned to 100%... If the wire spring on the rheostat is tanked sometimes the dome light will stay lit (other times you won't get instrument cluster lights). |
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| Author: | '67 Dart 270 [ Sun Feb 11, 2018 10:04 am ] |
| Post subject: | Re: dome light |
Thanks guys, yes, all three suspect points were on my mind, door switch, light switch and new seats. My light switch does turn on the dome light when rotated all the way counter clockwise. I'll do some testing and report back. Brian |
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| Author: | '67 Dart 270 [ Sun Feb 11, 2018 10:25 am ] |
| Post subject: | Re: dome light |
...my prime suspect is the seats, as they are newly installed so likely not a coincidence... |
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| Author: | '67 Dart 270 [ Sun Feb 11, 2018 11:25 am ] |
| Post subject: | Re: dome light |
Its the control module for the seats. When I unplugged the seats nothing changed, so I plugged them back in and then pulled the pigtail from the control module and voila, dome light out. It's interesting, how can the circuitry make a ground when the box is completely plastic, mounted to wood? Is it that the circuitry in the box is simply completing a ground path between two other wires? If so, I suppose that could still point to the door switches. Brian |
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| Author: | '67 Dart 270 [ Sun Feb 11, 2018 11:28 am ] |
| Post subject: | Re: dome light |
...because those wires to the door switch circuit are the only ones with power, the rest of the Sebring seat wiring goes to a fuse box that is switched power (using a relay) so there's no power in the system but for the door ajar switch wiring. I did notice the wires to the door switches was pretty twisted, maybe something is just barely touching on one of them. I have a couple new ones, I can swap them out and see if it changes anything. b |
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| Author: | '67 Dart 270 [ Sun Feb 11, 2018 12:18 pm ] |
| Post subject: | Re: dome light |
The door ajar switches appear to be OK. When I pull them and the wire end isn't touching anything, the dome light still has this low power lighting. I pulled the pigtail out of the seat control module and the dimly powered light goes off. I took a wire with two exposed ends. One end I put into the pigtail terminal for the door ajar circuit and grounded the other end, the dome light goes on full strength as it should. Same result for both wire circuits. So it appears that my wiring is not grounded anywhere between where I spliced into the door ajar circuits and up to the pigtail. If it were, then the dome light would still be dimly lit when I pull the plug from the control module. So, how does the module's internal circuitry make this ground? I'll measure the current in the circuit, it must be pretty low, but still... Brian |
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| Author: | '67 Dart 270 [ Sun Feb 11, 2018 5:45 pm ] |
| Post subject: | Re: dome light |
I used my piece of wire to test against the various other connections in the control module pigtail. I either got a ground, i.e. dome light fully lights up, or nothing. None gave me the low power lighting of the dome light. So, it appears that it is the circuitry in the module, providing a slight grounding in the dome light circuit. Doesn't appear to be a short in the wiring. I don't believe it's drawing much current. The LED bulb draws very little at full brightness, and it's just barely lit in this condition. I have a battery cut off switch, which I'll use when the car is off, otherwise this condition doesn't exist when the key is in the acc or run position. Happy to hear any thoughts on this. Brian |
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| Author: | Pierre [ Sun Feb 11, 2018 7:38 pm ] |
| Post subject: | Re: dome light |
Can you point out the schematics so we can see how everything ties in? Why does the seat module need to tie into the dome light anyway, or do you just need a switched door open ground? No idea why a stinkin seat would need either.... As mentioned, either there's a better point to tie it into the car or it can be isolated with a diode. Depending on what the module is doing with this though a diode may have an adverse affect. Perhaps a strategically placed relay. |
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| Author: | emsvitil [ Sun Feb 11, 2018 8:09 pm ] |
| Post subject: | Re: dome light |
I think I have a solution, just verify the following: When the power lead to the seat is connected, the led is dimly on. When the power lead to the seat is disconnected, the led is off. If that's the case, the ground for the led is backflowing (somehow) thru the seat module's power lead and find some sort of ground. Solution: Add a diode to the power lead to the seat module to current can only flow to the seat and not backflow. |
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| Author: | Pierre [ Sun Feb 11, 2018 9:52 pm ] |
| Post subject: | Re: dome light |
Power lead? As in the main power feed? That's going to be one fat (expensive) diode that has to survive the current the motors will draw and a complete waste of energy. The better way would be to put the diode in the lead going to the switch, again, depending on exactly what/how it's being used (the forward voltage drop may cause issues). This would be a sub $1 axial package easy to use type. |
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