What I found in my 1986 244 back-up light problem.

It was the connector on the left tail light. Yes, you have to pull the spare to get the cover off.

The wire route is:

Black from the harness (from the shifter switch). It it connected to one of the thingies (scientific name?) in that connector that pinches onto the circuit board foil.

That bit of foil is double wide. There is another black wire pinching thingie right next to the first one, and that one picks up the voltage and carries it over to the right side back-up light.

[Note that the rear fog lights on the 1986-88 (which have two lights, not one) use the same system.]

The foil under the first connector gets oxidized and pitted, and contact gets lost. Thus - no back-up lights.

Quick fix: Remove the two pinching thingies from the connector and trade their positions. That will put the incoming voltage on a good spot on the foil, the thingie for the right side will be on the bad spot.

You should get the left back-up light to work, and maybe sometimes the right side. One will get you going, right?

Good Luck,

Bob

:>)