Problem with Gauges and Brake Pedal

[robphelan]

OK... the generator light on my '74 2.0L has been coming on and off regularly. When it was lit, I noticed that my rear driver's side blinker would not work.

I figured it came on because my battery needed to be replaced badly - i had to jump it everytime I wanted to take it out.

So, after some weeks, I decided to replace my battery. Now, my generator light is still on, but when I press on my brake pedal, my Tach and Gas Gauge stop working! They just slam back to 0.

When I let up from the pedal, the gauges work properly.

I can't verify that the generator light has been constant just AFTER I replaced the battery though.

Any ideas?

Thanks,
rob phelan

[efeinsmith]

Verify for ALL grounds at the front and rear lights. If a ground is missing or defective, then you will get real strange symptoms, including flaky guage indications (I had that after some body work where they forgot to reconnect the ground on the front right directional indicator).

Eric

[rockaria]

Check your fuses. This happens with a certain blown fuse, Can't remember which at the time, but there are only a few.

[philinjax]

You likely have a bad voltage regulator or alternator. Your brake lights pull just enough amperage to lower the battery voltage sufficiently to cut out your tach and gas gauge.
I would exchange the voltage regulator first. Your battery is not getting charged.
Phil

[HarveyH]

The problem wuth the gauges happened to me a few weeks ago. It's Fuse 9. Doesn't have to be blown, just corroded enough to give a high resistance contact. Clean the contacts (Probably all of them need it) and clean or replace the fuse.
Harvey

[philinjax]

I think Harvey may be correct. If not, change the voltage regulator.
Phil

[robphelan]

Yikes! HarveyH was exactly right! I pulled #9 fuse even though it looked fine (actually better than a couple of others) and replaced. the tach stayed level when I applied the brake.

Thanks a bunch.. i would have spent a lot of time tracing grounds otherwise.