Home Up


Sunpass Repair

MVC-686L.JPG (44635 bytes)  I know many of you likely have Sunpass transponders in your vehicles.  This applies to the active ones with the display. If you don't have that model, none of this applies. (click on the images to see them full size.)

This is what happens if you don't change your batteries.   They leak.  Think about the environment they're in.  Florida sun and heat will kill any battery fast.

MVC-688L.JPG (27056 bytes) 

 Duracell used to guarantee that if batteries leaked in a device they would repair or replace it for free. Not any more. Now they only guarantee not to leak IF the leak happens before the date code on the battery. While I thought that date code was a marketing trick to show how long they're last, it was actually a way to get out of paying off for leaks.  The batteries in a SunPass WILL leak. 


MVC-675L.JPG (43353 bytes) MVC-677L.JPG (31410 bytes) MVC-676L.JPG (44147 bytes)  If you catch it right when the leak starts, you might be able to clean the terminals. I wasn't so lucky. Here's the damage. The batteries are at the top and the damage goes down. Nice design. The end that connects the two batteries totally failed.   The plastic even broke off.  This case will never hold another battery.   

It didn't seem like much had seeped into the case. Once it gets on the PC board, get a new transponder.  So I decided to give it a new battery pack.  Normally you would open the case to work on the PC board inside.   But I was worried that there would be a booby trap of some sort that would permanently disable the Sunpass for security reasons.  So the rest of the operation was done from the outside.  Or minimally invasive if you prefer.  

MVC-687L.JPG (52282 bytes)  Here are the parts.  The battery case is from Radio Shack, part number 270-414.  Could I have gone with the AA to upgrade?  Yes, and they would last longer.  But I sort of want them to run down more often to force me to replace them.  The tabs on the right are the battery contacts that were removed.  Note that they're chromed, so you can't solder directly onto them.


MVC-679L.JPG (46889 bytes) MVC-678L.JPG (52419 bytes) 

MVC-684L.JPG (48754 bytes) MVC-680L.JPG (45924 bytes)  


Here are some shots that show as much of the inside as I can.  It's hard to see, but I basically removed the + and - terminals from the top side.  That leaves two slots to insert the wires from the battery pack.  There is another board below this one separated with some foam tape.  You have to make sure you don't let the new wires protrude below the PC board any more than the tabs did.   None of this is surface mount, so it's not hard to solder.  The tricky thing is the plastic case.  You'll need to trim some of it out to remove the tabs.  You could do it right with a Dremel tool, but I just used a sharp knife, soldering iron and a pair of tiny cutters to trim the plastic.  I put a notch in the battery cover for the wires.  Yes, with a little more time and patience, you could do a much neater job than I did.   I just wanted to do a quick proof of concept that a Sunpass could be saved.  Although the battery case sort of looks like a 9 volt battery, it's not.  Don't even try it.  You need 3 volts (1.5 AAA x 2 batteries)

I loaded the batteries and it powered up just fine.  It even remembered my balance.  When I put it all together I tywrapped the battery to the bottom of the case.  Again, not pretty, but if it leaks again, it will drip to the dash, not the inside of the Sunpass.  The proof was the drive through the toll booth.  Perfect beep.  Now that my AAA's are external, the next repair will be easy and only cost me $1.59

Do yourself a favor, get a couple brand new AAA batteries, change out the batteries right now, need it or not. Put a reminder in your calendar to change them again before they expire.


Except for portions owned by others, Copyright: Ray Vaughan, 2008