77 308-blinker/reverse light prob. revisited..

First thing to do in that situation is to fix all the grounds to the rear lights.

 

Greg -- Have you made any functional measurements to check Brian's suggestion or just a visual inspection? For example, if you measure the voltage between the ground terminal at the turn signal light socket and a good chassis/engine ground (while the bulb is flashing), it should remain ~0V. If the voltage "jumps up" to something like a few volts or more when the bulb goes "on", then the grounding is actually not so good.

 

Correct -- you've got the right picture (and, as I've said before, the most important tool to DIY on a Ferrari = multimeter ).

This kind of thing isn't a "crossed connection" as much as it's a poor connection somewhere -- like at the crimp between a wire and a terminal or between a terminal and a threaded stud. Might not be your problem, but it's a likely thing to check first and rule in or out -- hence Brian's suggestion.

Do you have any aftermarket mods that are seriously hacked into the wiring (alarm that flashes the ext. lights, etc.)?

 

They do ground thru the harness, the black wire makes up to the base plate on the assembly I'm looking at....blue to the brake lights, red/blk stripe to reverse.

 

Where the turnsignal AND the back-up light are flashing at the same time makes me think that there is a reverse polarity problem.

In other words, both lights are getting voltage through a common ground wire, voltage running backwards so-to-speak. This can be caused by a short in the system supplying power to the chassis, taking the path of least resistance back through the ground.

If the lights are grounded back through the harness then another possibility could be a short in the turnsignal switch itself.

It sounds odd but I have seen numerous times.

 

i once had a tr3 that when i stepped on the brakes the brake lites lit and one headlight. never could find out why. in addition to the multi meter you might get this thingie, not sure what it's called, but it put it's own current in the line. good for checking complete circuits. like starting at the taillight and working back to the fuse block.good luck. perserverence furthers. also in the old days we used hand signals for turns. if all else fails.

 

When you have an insufficient ground in the lighting system, turning on the flashing lights (or the brake lights for that matter), an "articial" ground is created through one of the other bulbs.
This bulb will then light up as it is now in series with the "original" bulb. Both bulbs will be light up, but weaker.
You often see this on older italian cars. FIAT from the seventies and teh eighties were especially prone to this.
Find the grounding points in connection with the rear lights, clean them up and I'm sure your problem is solved.

 

Greg -- Are the reverse lights themselves working OK? -- i.e., when you select reverse (with the key "on"), do the reverse lamps, and only the reverse lamps come "on", or do you get a more "colorful" display?

 

Audi was notorius for this also.

 

it might fix itself. i haven't had windscreen wipers since, like aug. started the car up today and the wipers came on. why? i dunno.