Just started up my car, first time in 2 months, car is never driven, up on jack stands, concours restoration 99.99999999999999999 complete, and has been for 3 years. Anyhow, EVERYTHING is perfect on the car,until I tried the left map light, ( I test everything each time I start it) when I did, courtesy lights died, no map light, removed fuse, yes it was blown, tried new fuse, tried left map light again, same result, blown fuse.
Anyone have any ideas
Thanks in advance
You will need to make one of these to get started. IF a short is present, instead of blowing the fuse it will light up the light bulb.
Then you need to start by pulling the lamp out and seeing if the light lights up when you switch on the courtesy lights. If so the short is in front of the light in the circuit.
And for clarity, which courtesy light are you talking about exactly? The one in the rear quarter or the overhead in an XR7?
Well that sure is a fancy looking contraption, if possible, a step by step as to making it, I recognize a light bulb, and the wire, and the pill bottle, but nothing else looks familiar .
To clarify, every courtesy light works, rear roof pillars, under dash, glove box, doors ( XR-7), the fuse blows when I use the toggle switch for the overhead map light, ran out of fuses today, bought some more tonight, intend to see if it’s only the left map light toggle, or perhaps all of the toggle switches.
Is there, (can’t remember), a junction box/connector, that all the toggle switches wiring connects to, before going to fuse box?
How to build the test light.
The pill bottle is just there to protect the lightbulb. You can use anything that will let you see the light and protect the bulb from other stuff in your tool box.
The wires are soldered to the bulb. One lead is soldered to the two contacts on the bottom of this 1157 tail light bulb, and the other is soldered to the side of the bulb. (Any 12 volt bulb will do).
On the other end there are two .250 faston style female spade connectors. Those connectors allow you to switch different types of fuses on the end of the wires.
For glass tube style fuses, you start with a blown fuse. sometimes the ends will twist off a blown fuse, but if needed you can just break the glass and remove it. Then I use the legs of a blade style ATC fuse (again, start with a blown fuse and just rip the legs out with a pair of pliers. The legs get soldered to the fuse ends, and they serve as male spade lug connectors and fit the faston female spade lug connectors.
For ATC style you will start with a blown fuse. There is an adapter that allows you to tap power from an existing fuse. Get two of these. Car stereo installers call them ATC fuse taps. Grind the male end of the tap small enough to fit into a mini ATC fuse socket. You can now test most types of circuits without having to buy a couple of boxes of fuses.
Don’t do this:
Looking for wiring diagram. I think it may switch ground not power…
Hope you find diagram, as I with you until you start talking about using the taps to hack onto a good fuse, all that’s showing me, is that the bulb works, the test bulb.
Not the circuit for the map light, I’m assuming the toggle has gone bad, the main connector for all of the toggles, IF there is one, or the actual connection at the map light overhead.
The test bulb will only light up if the circuit has power running through it. when you hook it up to a circuit with the lights turned off it will not light up. then turn on the power, it will light up. Turn the power off and then remove the light bulb from the fixture your testing, if the test light stays on you have a short some place in the wiring. You would be surprised how often a bad bulb will short out.
Good luck.
I think xr7g428 is great, so don’t get me wrong, not trying to cap on anyone. That is a very ingenious tester, and will keep from blowing fuses, but only shows that current is flowing past it. You could tell if there was a short if it lit at the wrong time, and disco connections until it goes out, but still just kind of poking around.
The proper tool is a VOM - volt/ohm meter. A wiring diagram would make quicker work of it, as has been mentioned you are not sure if the lamp is ground switched or load switched. The courtesy lamps are daisy chained and generally load switched (supplied with voltage rather than connected to ground.)
Map light may be a different circuit, or is tied to the others, not sure about that. It is supposed to come on with courtesy switch as well as toggle? Then the 2 circuits would be connected…
I do not know the year, but I am guessing it is load switched and independent. Since the short happens when you toggle the switch, the short is at the switch or past it.
Remove the bulb from the socket and toggle the switch…if the fuse blows it is the switch or wiring to the bulb.
If not, it is the bulb or socket.
The fuse blows because the voltage cannot go through the bulb to absorb the current load, and only blows when the switch is flipped, so the short is in between the 2.
Generally, you just follow the power supply line down the chain (with the bulb removed) looking for zero or low resistance from the checkpoints to ground.
To determine the power supply lead, use the voltage function (with battery power on) to check which pin has 12v on the switch when in the off position.
Do resistance checks with power off.
If I’m reading the wire diagram right, the map light switch gets power from the fuse box on wire #54 grn/yel to the switch, (this wire feeds all four of the toggle switches) then wire #124 brown, goes to the left map map light. If the only switch that blows a fuse if the left map then I would assume that the problem is between the switch and the bulb. The harness runs from the switch to the right door jamb makes a connection there and goes down the pass door sill and makes a connection there, splits and goes up and down the roof to the console where there are multiple connections. The power wire #124 also powers this circuit thru the headlight sw, and door jamb switch. Hope this helps!
Okay I found an XR7 wiring diagram that includes the overhead map lights. The switch is switching 12 volts so that tells you that the short is after the switch, and before the lamp. (the fuse doesn’t blow or the test light doesn’t illuminate, until you flip the switch) My best guess is that the two Philips screws that hold the over hear console could be the culprit. Possible one of them has pierced the insulation on a wire.
If you built the test light, you can flip the switch and as long as there is a short to ground the lamp will stay lit. The over head console is held in place by the two screws at the front and two blind clips at the back. I would remove the screws and watch for the lamp to go out.
The real value of the lamp tester is that you may find that you have a wire that is being pinched some place and the short may be intermittent. The short can be any place between the switch and the lamp. I always look for pinch points, and especially screws, in the path of the wiring. I located a very difficult to find short in the wiring for a power sunroof that was being pierced by a sun-visor screw on the passenger side. I have also found many shorts under the door sill plates and from the ground screw for the under dash lights in the upper kick panel area. It would be almost impossible to intentionally spear a hidden wire, but I seem to be pretty good at it unintentionally.
You can do all of this testing and more with a VOM and I do recommend having one and learning how to use it. I find the lamp useful as it doesn’t require as many hands to operate. You just stick the two ends into the fuse box and watch for the light to go on or off.
Thanks everyone. Thanks for finding the diagram. Questions remain, although your answer sounds very plausible.
Is there more than one wire traversing the route from the toggle (switches) to the map lights, ( does the left have it’s own wire, and does the right
have it’s own wire) ?
Or do they connect sometime after the toggle switches?
Is it possible for the 12v going to the toggle, to “just be there”, and when you flip the toggle, to make a contact, could the short be there?
While I love the possibility of the screw on the overhead console, or a pinch in the route of the wire, I highly doubt it, I will check the screws
tomorrow.
My reason for doubting, is that the car has not moved one inch in three years, it has been on jack stands, and the wiring/bends in wiring route
screws, have all been completed for over 4 years. No flexing of the body, no twists, no bumps, so I would assume, the wires have not rubbed
on anything.
two wires, one from each toggle switch to each lamp.
No, they are independent circuits.
The switch could have failed internally in some unpredictable way. It is possible.
These things are tough to trouble shoot. I had a tiny spot of weld splatter that eventually rubbed through a wire under the center console in a Cougar and that wire hadn’t been moved since the car was built. I have no idea why it picked that particular moment to act up.
You need to update what you have found for us to go any farther with troubleshooting this. We have to eliminate some variables.
No that problem was solved, thanks to you and others who helped, bad switch. I posted 2 NEW problems, one asking about the differences btw a left and right toggle switch, WCCC sent me a right toggle map switch, and I ordered a left map toggle switch, the wiring diagrams seems to show that the left and right are identical, perhaps that’s why I was sent a right side, called on Fri., have to call back Monday to talk to the “electric” pro.
Part 2 is steering wheel problem, on my post of " help, help, help"
Got it. If it plugs in it will work.
If we’re talking '69 (did not see a mention of the year anywhere), there are two places (two prong connectors) to plug the map light (or is it clock?) on the PS above the glove box. If you plug into the wrong one, you will have the problem you have described.