99 EX All lights randomly turn off while driving. Much help needed.

[Twdeleeuw]

Hello All,

I am brand new to posting to this forum, but have garnered a ton of help from you all in the past, to which I am very grateful. My newest problem....

I have a 99 EX Limited 5.0L. While driving at night with the lights on auto, at random times, all of the lights, exterior and interior (dash lights, etc) turn off. I also notice that the green auto indicator light on the rear view mirror also turns off. If I tap the mirror, everything turns back on. Sometimes they turn back off on their own. Sometimes I tap the mirror again and they turn back off. Sometimes they stay on and I have no more issues. If they shut off and I turn the light switch to ON, everything is well. With the lights in ON, I can sometimes see the green auto light indicator flashing on and off, but the lights remain constant. While that green indicator turns on and off, I hear clicking in the cabin, similar to a relay clicking. From what I have read, you all recomend changing the MFS. I have done that fun an unrelated issue, and no change to the interior/exterior shutting off problem.

ALSO, If I turn the dimmer switch for the interior lights, all the interior lights go wild as I turn it, flashing on and off with the same clicking noise as they flash. Not sure if this is related.

I have no idea where to start. Any help is greatly appreciated. Thank you.

 

[J_C]

Dimmer switch, take it off, clean off the tracks and metal rollers after degreasing it, then apply a fresh, thin coat of dielectric grease.

If tapping the mirror gets it working again then you probably have a similar problem with the mirror resistive slider mechanism, but i do not know if that can be disassembled, so I would try spraying contact cleaner in the slot and move the slider back and forth several times, but be very careful not to get any up behind the glass. I don't know what would happen to the glass coating or the electronics to auto-dim. You can buy that mirror on ebay and elsewhere but it is not cheap, $100-something dollars for new aftermarket brand, IIRC. A junkyard would definitely be a cheaper alternative though no idea how well those weather if exposed to the elements. One brand and model # is Gentex GNTX-156, at least that works on my '98 XLT with the slider, photocell and auto-dimming, don't know if '99/Limiteds had any changes to the mirror.

 

[fast_dave]

What JC Said - Dimmer Switch ^^^^^

Here's a link to a write up I did on refurbishing it - it's built like a tank and takes well to refurbishing

LINK: How to refurbish a 1998 Dimmer Switch

Hope that helps!

 

[Twdeleeuw]

Dimmer switch, take it off, clean off the tracks and metal rollers after degreasing it, then apply a fresh, thin coat of dielectric grease.

If tapping the mirror gets it working again then you probably have a similar problem with the mirror resistive slider mechanism, but i do not know if that can be disassembled, so I would try spraying contact cleaner in the slot and move the slider back and forth several times, but be very careful not to get any up behind the glass. I don't know what would happen to the glass coating or the electronics to auto-dim. You can buy that mirror on ebay and elsewhere but it is not cheap, $100-something dollars for new aftermarket brand, IIRC. A junkyard would definitely be a cheaper alternative though no idea how well those weather if exposed to the elements.

Thanks J_C. I was unaware that the resistive slider in the mirror had any control over the exterior lighting while the car was on. The auto light photocell is also in the mirror. Could that be related? Perhaps a bad relay triggered by the photocell?

 

[J_C]

Since tapping it helps, I doubt it has anything to do with the photocell, unless it has a broken solder joint but it would seem odd to me that it worked this long before failing since a photocell does not create heat like other parts more commonly ending up with bad solder joints.

The resistive slider can completely turn the exterior lights off when set all the way to the left, or sliding right, how long they stay on after the ignition is off. You might not even need contact cleaner, just sliding the slider back and forth several times, though it probably has little metal spring contacts and if they are loose, there may be nothing that helps besides opening it and trying to bend a little more tension in them. Again I do not know if the mirror assembly can be non-destructively opened. I've never tried nor have I seen anyone else, but you might find more info with a forum search. It is essentially a linear potentiometer except that at the left end of its travel it completely disconnects the circuit.

Relay seems unrelated if manipulating the mirror changes anything because the relay is remotely located in a box under the dash

 

[mic98xlt]

Just disconnect the wire harness or connector on the back of the mirror. The headlights will should work normally without any interference from the switch on the mirror. Once you have proven that your problem to the mirror the JY would be my next stop. GL.

 

[Twdeleeuw]

Just disconnect the wire harness or connector on the back of the mirror. The headlights will should work normally without any interference from the switch on the mirror. Once you have proven that your problem to the mirror the JY would be my next stop. GL.

Thanks. What do you mean by JY?

 

[mic98xlt]

Junk yard.

 

[Twdeleeuw]

Thank you all for the help. Now that it's dark, I went out and fussed with the slider on the mirror, and behold, the problem was replicated. Turns out, the slider was already in the off position, so that's some serious contact issue. I'll check it out and report back with the results. Again, thank you.

 

[mic98xlt]

In the "Off" position the auto mirror switch really goes "Bonkers" when the mirror switch is bad. The junk yard's that let you pull your own parts had so many, I got several mirrors years ago to ensure I had picked a good one.

 

[Gary Crist]

Them Cali guys do not know "JY" just "Pick A Part! Then they know...

he he he

 

[masospaghetti]

My departed 96 XLT had the autolamp switch, and caused me to lose all lights a few times driving at night. It certainly wasn't my favorite feature after that....

 

[mic98xlt]

Them Cali guys do not know "JY" just "Pick A Part! Then they know...

he he he

Lol, an education for me.