How do I increase amperage so that both reverse lights turn on?

[cjvanderah]

I have a 2002 Ford Taurus Wagon. The reverse lights will not come on so I did the usual troubleshoot step by step. Checked the fuse...working. Checked the bulbs...filament intact but replaced both to be safe. Next I googled and saw that it may be the Digital Transmission Range (DTR) Sensor. So I went and bought one from NAPA...42 bucks...replaced the part and figured that was that. Ended up not solving the problem...

So then just by pure luck I took out one of the reverse light bulbs while the car was in reverse...and then noticed that the other reverse light then came on! I plugged the one I had in my hand back in and then the other light turned off! I replicated the experiment with the other bulb and same thing happened. As soon as one was unplugged, the other light turned on. Didn't matter left/right.

So it seems the issue is now a matter of having enough "juice" getting to the bulbs so that they both turn on when the bulbs are in. I'm a DIY kinda guy, but this is beyond my knowledge.

Solutions/suggestions are welcome and thank you so much in advance for the help. I have to get the car through inspection and there's no way that's happening when the reverse lights don't kick on.

[pawpaw]

Welcome to TCCA

Good trouble shooting, maybe a voltage drop problem, look for a bad ground for those lamps, or maybe a B+ feed problem, like corroded pin/socket connection, or splice to the rear lamps, such that both lamps load cause the battery voltage to drop across the faulty connection.

If you have a multimeter, perform some voltage drop tests, to determine if you have some bad connections. If you've not done voltage drop testing, there are instructions in the "Battery Tutorial" sticky atop this forums index page.

If you don't have a multimeter, you could rig a ground test jumper lead, one end to a good clean unpainted body spot, the other end as a test probe to provide a parallel ground connection to each lamp & maybe able to narrow down the faulty ground question, as your probe would cause both to light up if you have a faulty wiring ground.

You could do the same with a fused jumper for the B+ feed, if you come to suspect it.

Let us know how your trouble shoot goes.

[behlinla]

The way to increase amperage is to reduce the resistance of the circuit. In this case it sounds like you have bad connections causing the high resistance and low current.

I would start with checking the grounds. You can follow pawpaw's tips. Check the voltage on each side of the bulb in reverse. One side should have battery voltage and the other side should have close to zero volts. If you have a bad ground you will see a high voltage on the ground side. Bad connection on the supply side will cause lower volts to get to the bulb.

[WJC]

Ground for that circuit is at the base of the left A pillar, behind the kick panel. First check the wiring loom running through the tailgate, very common on Ford wagons for the copper conductor to break up where it bends. Black wire/pink stripe.

[cjvanderah]

Pawpaw, behlinla, WJC - Very much appreciate the suggestions. It was dark by the time I wrote the post, but I'm out taking a crack at it again today. I've taken much of the interior plastic off the tailgate and poked around to see if I could find any exposed wiring, but it's tough to see anything since it's all pretty much taped. I think I've found out where the ground is, but I don't see anything out of the norm. I'll do some voltage drop tests and see how that goes. I'll keep you updated on progress. Thanks again for the suggestions and if you think of anything else please don't hesitate to post. Super rookie when it comes to electrical work on a vehicle. Thanks.

[lcjones]

CJ,

Any update on your reverse light issue? I have an '03 wagon with no reverse lights as well.

Chap