High Mount Third Brake Testing Question

[Muscam1]

Howdy from Oklahoma!

I'm new to this board and have spent the last hour searching for tips on troubleshooting the high mount third brake light for a 97 Explorer. I picked up a ballast and light from my local JY and thought I could do a quick swap starting with the ballast first.

Well - no luck the JY ballast and light. They don't work either. I benched tested both the JY and the Explorer's ballast and the output seems to be around 100 millivolts which doesn't make sense. Thought it should be at least 80v to power the neon strip light...so that may be my problem.

I also tested both the JY and the Explorer's neon light strip with a meter to see if there was continuity - and there wasn't for either light. Normally that would mean there is a break in the light circuit. Would that logic also apply to this neon setup.

Thanks--Marc

PS - Great site - I could spend days here.

 

[gmanpaint]

Howdy from Oklahoma!

I'm new to this board and have spent the last hour searching for tips on troubleshooting the high mount third brake light for a 97 Explorer. I picked up a ballast and light from my local JY and thought I could do a quick swap starting with the ballast first.

Well - no luck the JY ballast and light. They don't work either. I benched tested both the JY and the Explorer's ballast and the output seems to be around 100 millivolts which doesn't make sense. Thought it should be at least 80v to power the neon strip light...so that may be my problem.

I also tested both the JY and the Explorer's neon light strip with a meter to see if there was continuity - and there wasn't for either light. Normally that would mean there is a break in the light circuit. Would that logic also apply to this neon setup.

Thanks--Marc

PS - Great site - I could spend days here.

This might help, might not.

I had the same trouble after i got my '95. I learned a little something from this forum.

Try this:
Under the rig, on drivers side, all the way in the back, in the corner of the rig. Climb under on your back, look upwards in front of the rear bumper. Look for a round gray connector. This is the trailer light connector. Unplug this, clean it out with spray contact cleaner. Let dry. Now before plugging back up, go press your brake pedal. You just might see your third light working. Now plug the connector back together, and try your brake pedal again. If all is good, your done. If third light fails to come on, unplug the connector, and leave off. If you need a trailer light connector, just hardwire into brake lights.

Hope this helps, it did for me, after hours of messing with the light.

 

[team]

I just got done converting mine to led and I only have a little over 20 dollars in parts. I got a 30 led red light strip from superbright leds, gutted the neon tube out, then hot glued the led strip in and wired it to the 12v two wire connector that went to the ballast. Very simple and it looks completely stock.

 

[96eb96]

Howdy from Oklahoma!

I'm new to this board and have spent the last hour searching for tips on troubleshooting the high mount third brake light for a 97 Explorer. I picked up a ballast and light from my local JY and thought I could do a quick swap starting with the ballast first.

Well - no luck the JY ballast and light. They don't work either. I benched tested both the JY and the Explorer's ballast and the output seems to be around 100 millivolts which doesn't make sense. Thought it should be at least 80v to power the neon strip light...so that may be my problem.

I also tested both the JY and the Explorer's neon light strip with a meter to see if there was continuity - and there wasn't for either light. Normally that would mean there is a break in the light circuit. Would that logic also apply to this neon setup.

Thanks--Marc

PS - Great site - I could spend days here.

A neon light will not have DC continuity, it is actually a plasma state device (gas between two electrodes) that begins to conduct with high voltages. The ballast has to kick start the bulb first with a very high voltage then it settles down to a lower voltage and illuminates. Be careful, you could get a nasty shock if you arent sure what you are doing. The system is actually very similar to a florescent tube or what is in an LCD TV.

It is likely the JY bulb or ballast is bad too. Once you confirm 12V at that upper connector, if a bulb/ballast combination does not work there is nothing really to trobubleshoot. I believe you need a neon tester to check the ballast.

Either go the LED route or try another junkyard one. A few years ago I found a junkyard selling them for like 5 or 10 bucks, and I bought 3. Should outlast last the life of the truck...

 

[Muscam1]

THANK YOU VERY MUCH 96eb96!

Exactly the info I was looking for.

Also...thanks to the other posters. Good tip on the trailer hitch connection and an LED bulb replacement replacement may be my next "job."

--Marc

 

[Muscam1]

Ended up being the ballast

Thanks again to everyone that helped me

--Marc

 

[gmanpaint]

Ended up being the ballast

Thanks again to everyone that helped me

--Marc

Did you find a way to test the ballast? Have a couple of them laying around, it would be nice to know if they are good or not.

 

[Muscam1]

I picked up another light and ballast from the JY. I benched tested them both together and they worked. I then replaced just the ballast on my Explorer and that fixed the problem.

While bench testing I tried to read the output of the known good ballast but for some reason I couldn't get any readings. May be that my multi-meter couldn't handle that many volts.

--Marc

 

[tnhusker]

I just got a 97 with the same problem. I have a couple questions. Where is the ballast located? And how do you remove the light?

 

[Vallince]

I know this is an old thread but can anyone here clear up what the output for the ballast to the bulb is? trying to find a brand new Ballast that even if it isn't OEM as long as the input/output specs are the same i might be able to jerry rig one in there.

 

[donalds]

I still say led conversion is your best bet
Ford fixed this problem by changing the light to LED

 

[J_C]

I know this is an old thread but can anyone here clear up what the output for the ballast to the bulb is? trying to find a brand new Ballast that even if it isn't OEM as long as the input/output specs are the same i might be able to jerry rig one in there.

I'll give you my best guess which is not based on much but vague memory, and could be wrong, then if you use this info and blow up the bulb, fry the ballast, or burn the vehicle to the ground, I don't accept responsibility.

It's a small tube and neon ballast so probably in the neighborhood of 90V (AC) and just a few tens of milliamps if that. Can't use a fluorescent tube ballast (usually, is much higher voltage), best would be getting a new tube that you know the drive specs for, in order to pick a compatible ballast, or as donalds already mentioned, convert it to LED. Keep in mind the enclosure if you get a different tube, don't want heat melting the plastic or overheating the ballast. I would have to test it to know but would guess that much over 4W, and even less than that if touching plastic, would be too high power a tube.

It also seems like it would be hard to find a compatible ballast that is not just electrically compatible (which may be the easier part) but also custom shaped to fit within the available space, receives enough cooling in that space, and weatherproof.

Unless you are trying to do an all original restoration for a high value show truck (and an Explorer is not really the best candidate to bother with for that purpose), convert it to LED. There are red LED strips dirt cheap on various sites like aliexpress or ebay, little higher on amazon, and a series current limiting resistor to factor for keeping a strip designed for 12V, at low enough current at the vehicle ~14.4V alternator output. A google search will find sites with a series LED resistor calculator to determine the best resistor value for a 12V series array of LEDs (12V forward voltage) on a 14.4V supply.

 

[Vallince]

I'll give you my best guess which is not based on much but vague memory, and could be wrong, then if you use this info and blow up the bulb, fry the ballast, or burn the vehicle to the ground, I don't accept responsibility.

It's a small tube and neon ballast so probably in the neighborhood of 90V (AC) and just a few tens of milliamps if that. Can't use a fluorescent tube ballast (usually, is much higher voltage), best would be getting a new tube that you know the drive specs for, in order to pick a compatible ballast, or as donalds already mentioned, convert it to LED. Keep in mind the enclosure if you get a different tube, don't want heat melting the plastic or overheating the ballast. I would have to test it to know but would guess that much over 4W, and even less than that if touching plastic, would be too high power a tube.

It also seems like it would be hard to find a compatible ballast that is not just electrically compatible (which may be the easier part) but also custom shaped to fit within the available space, receives enough cooling in that space, and weatherproof.

Unless you are trying to do an all original restoration for a high value show truck (and an Explorer is not really the best candidate to bother with for that purpose), convert it to LED. There are red LED strips dirt cheap on various sites like aliexpress or ebay, little higher on amazon, and a series current limiting resistor to factor for keeping a strip designed for 12V, at low enough current at the vehicle ~14.4V alternator output. A google search will find sites with a series LED resistor calculator to determine the best resistor value for a 12V series array of LEDs (12V forward voltage) on a 14.4V supply.

Thanks for the info, It seems i have an up hill battle for this restoration project. my aim is to keep it original as possible so if can keep it neon i would like to. The explorer used to be my moms and so i do cherish the heck out of it. i suppose i could convert it to led as you said but the peppered individual lights going across the bar isnt the same as a solid bar of red color.

 

[Mbrooks420]

If you want original, I’d just source a used one. Find a pick and pull truck that looks like it’s been garaged, and it’ll probably be fine. I’ve never had one of these fail, so working options should be a possibility.

 

[dudemancool1904]

There’s a dude on eBay that sells verified working original bulbs and ballasts. But you’re looking at spending $150ish.