Wiring experts: plz help identify short circuit

[six50joe]

I've just tested BLUE/YEL on the personal light by connecting the - to the cig lighter center pin as Rickl has advised, with a multimeter. Since I didn't know how to disconnect the blue/yellow wire plug itself (as seen in the photo), I traced the black wire it lines up with on the opposite end to a solder point, and put + there. I must admit I didn't expect this but I'm getting 12V on it! Good thing I've been following your advice instead of my own instincts.

I didn't do this same test on the dome light yet, mainly because I don't have handy a long enough wire to test with at the moment.

Does this tell us then that the problem has to be in the personal light itself- or am I misreading the results of this test?

[Rickl]

Originally Posted by six50joe

I've just tested BLUE/YEL on the personal light by connecting the - to the cig lighter center pin as Rickl has advised, with a multimeter. Since I didn't know how to disconnect the blue/yellow wire plug itself (as seen in the photo), I traced the black wire it lines up with on the opposite end to a solder point, and put + there. I must admit I didn't expect this but I'm getting 12V on it! ........................Does this tell us then that the problem has to be in the personal light itself- or am I misreading the results of this test?

If you put the - lead of your multimeter on the cigar lighter center pin,(with the ignition turned on so that you had 12v on the center pin) then your meter must have been reading negative 12v. You probably just didn't notice the negative sign.

This test shows there is a path to ground from the blue/yellow wire. If the blue/yellow wire had 12v like it should have, then your multimeter would have read 0v when connected to two points of the same potential (both points 12v in this case).

The problem is that you haven't proven if the blue/yellow wire is grounded, or if you are seeing the ground through the filaments of the dome/personal light bulbs. You will need to unplug the harness connector from all the lights at the same time, and then repeat your test connecting to just the blue/yellow wire. This connector is visible in your photo.



Depending on whether the blue/yellow wire is "open" or "grounded" will determine the best way to proceed.

[six50joe]

Actually I mis-wrote it; I had + connected to the cigarette lighter pin, and did have ignition turned on.

So then to clarify, is it necessary to disconnect the harnesses on both the dome and personal lights to test BLUE/YEL correctly?

[Rickl]

Originally Posted by six50joe

Actually I mis-wrote it; I had + connected to the cigarette lighter pin, and did have ignition turned on.

So then to clarify, is it necessary to disconnect the harnesses on both the dome and personal lights to test BLUE/YEL correctly?

What we know for sure is that your blue/yellow wire does not have 12v on it, like it should. It could be grounded, or it could be wide open. You can connect your multimeter from the blue/yellow wire to a known ground to double check your findings.

Your test with the multimeter shows that the solder point you connected to is grounded, but we don't know if the blue/yellow wire is grounded, or if the current is flowing through the bulbs filament and finding a ground through the manual off/on switch, or from a door switch. It should be easy enough to unplug the connector with the blue/yellow wire and repeat your test directly on the blue/yellow wire.

Since both of your lights are wired in parallel to the blue/yellow wire, you need to disconnect both of them at the same time when doing your tests. As long as the connectors are exposed inside both lamps, you should also check for voltage at both lamps.

[six50joe]

OK, yesterday I disconnected the wiring harnesses for both dome and interior lights. Tested cig lighter pin to each each wire, multimeter readings:

Personal light- white (middle wire) 12V, other two wires 0
Dome light- red 12V, white 0

[six50joe]

(with ignition on)

[Rickl]

Originally Posted by six50joe

OK, yesterday I disconnected the wiring harnesses for both dome and interior lights. Tested cig lighter pin to each each wire, multimeter readings:

Personal light- white (middle wire) 12V, other two wires 0
Dome light- red 12V, white 0

The most important reading was for the blue/yellow wires which should have appeared in both lamp housings. If you are saying that these both read 0 volts, then that shows that the 12v supply wire is not grounded (that's good). On your previous tests you proved that it did not have 12v on it either.

Since this is true for both lamps, it means that the connection from pins L6 and L7 of the junction box are open, while pin F10 is working normally.

It is unlikely that two wires (L6 and L7) both became broken at the same time, so it is more likely the internal connection between F10 and L7 has become broken, possibly rusted away.

It would be almost impossible to fix this, so an alternate solution would be connecting the blue/yellow wire to another constant 12v source. This could be done near the junction box, or inside one of the dome lights if you can fish a new wire up there.

Of course this assumes that the corrosion inside the junction box has stopped. If it continues and additional wires break or short out to others, then you will have big problems.

[six50joe]

To make the fix at the junction box, it sounds like I'd still need to find the harness on the box and disconnect it, correct? If the J/B is what's in the photo I attached in an earlier post, I suppose I'd have to detach it from its mounting. Which of the two solutions would you implement?

[Rickl]

Originally Posted by six50joe

To make the fix at the junction box, it sounds like I'd still need to find the harness on the box and disconnect it, correct? If the J/B is what's in the photo I attached in an earlier post, I suppose I'd have to detach it from its mounting. Which of the two solutions would you implement?

Since I drive a RAV 4.3, I cannot verify if your picture is the correct block.If you have access to the electrical manual, it should have a diagram showing the location of all the junction boxes.

The electrical diagram should also show how the pins are numbered so that you can locate pins L6 and L7 (verify by proper color as well). I expect each of the connectors plugged into the junction box is a letter of the alphabet, and then the pins are numbered within the connector.

Once you locate the proper connector, it may just have to be removed and reseated to clean off any corrosion. Spraying all the connectors with some electrical contact cleaner may also help. Be aware that some contact cleaner can melt plastic , so test before using.

If that doesn't work, then after finding the two pins, you could cut the wires, and reconnect them to another source of constant 12 volts . Perhaps splice then back to the blue/yellow wire in position I5.

Just a word of warning that this is a bit of a hack solution. If it was my RAV I would prefer to replace the damaged parts and make the RAV like new. However that solution could cost $100's. If you want to save some money then this hack is the way to go, but keep in mind that the water damage may/not continue to worsen.

[six50joe]

Rickl, DD and Carbon, I owe you my deepest thanks with all your guidance over the past month, without which I'd still be lost in troubleshooting my electrical issues. Though the fixing the problem with the stereo it was trivial, I wouldn't have thought of it myself and my wife and toddler would still be without a radio throughout the day. Though the interior lights are still not fixed, with your help the problem appears to at least have been isolated significantly.

I did find an illustration that shows the location of the 'instrument panel' (attached), but unless any of you has had specific experience accessing it in a 1st gen RAV4 I suppose it would be difficult advising me at this point. Rickl, whether I implement a 'hack' solution or the proper fix, it sounds like I'd still have to get at the area where L6 and L7 are, if I want to avoid making the hack uglier and splicing my own 12V leads somewhere along the way. In the end if there's no other choice, I'll have to consider that; i'ts been a surprise how much you appreciate your interior lights when you don't have them at night

I removed the lower panel that appears to conceal the instrument panel J/B yesterday, and took a picture of what looks like it might be the back of it (attached), but obviously I'm not sure. Unfortunately I don't have a schematic that shows the layout of this J/B which might help to identify it. You can see the "J 4" label on it but I don't recall seeing that in any of the schematics I've had access to. Looks like it could be a challenge to get at. Any further advice you might have would obviously be a big help, but as mentioned I understand that it's probably hard to help here.

Regards,
Joe