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Posted by: tadink Aug 28 2013, 05:00 PM

Hey all -

73 1.7L FI in a 1971 tub, installed by McMark.

While driving today - I depressed the brake pedal and had the tach, gas go to zero, and the red ALT light light up. Release brake, gas / tach return to normal. Depressing the brake pedal provides NO BRAKE LIGHTS, so that is bad.

Turning on headlamps, operation normal.
Turning on turn signals - tach and gas drop to zero, no turn signals.
No Hazards - but that has been going on for some time.

Prior to this - turning on the turn signals lit up the big red light as the switch flickered, but it also did produce turn signals. Not any more.

When going over bumps - red ALT light flickers, when low RPM red light begins to glow, goes dark with higher RPMs.

Also - when driving today on the freeway after 45mins at high speed, developed a little stutter, not bad, almost un-noticable, not all the time. possibly not related - dunno.

ugh, I hate the elec shit.

where to start oh great and wise brain trust.....?????

thanks in advance....

td

Posted by: SLITS Aug 28 2013, 05:01 PM

Fuse #8 or #9 Don't remember which.

Posted by: r_towle Aug 28 2013, 05:03 PM

QUOTE(SLITS @ Aug 28 2013, 07:01 PM)

Posted by: tadink Aug 28 2013, 05:06 PM

damn, not only are you guys good, you're FAST!

I'll go look - will advise.

td

Posted by: Elliot Cannon Aug 28 2013, 06:24 PM

QUOTE(tadink @ Aug 28 2013, 04:06 PM)

Posted by: tadink Aug 28 2013, 06:43 PM

and, baddha-bim - 2 fuses WERE bad and have been replaced, providing hours of happy motoring WITH brake lights, such as they are!

thanks men - you are the best!

td

Posted by: sean_v8_914 Aug 29 2013, 07:32 AM

before i get into chasing ghosts I like to do a system clean up. this kills many common problems like voltage drop when pressing teh brake pedal

clean teh chassis ground above teh fuse panel

clean the fuses with a scotch brite pad. only rub in one direction so you dont rip the metal tab off

clean fuse panel fuse holding tabs

clean chassis ground in engine compartment next to relay board

clean relay board contacts and things that connect to it

clean chassis ground strap and attachment points on transaxle and under trunk floor

after 40 years , they all need this.

Posted by: sean_v8_914 Aug 29 2013, 07:35 AM

anyone remember where the 3rd chassis ground point is?

Posted by: 76-914 Aug 29 2013, 07:39 AM

left front under hood in front of headlight

Posted by: tadink Aug 29 2013, 07:55 PM

Hey all again -

appreciate the advice to clean up all the grounds - that may be my next task - but I need to ask - what are the AMPS for the FUSE for the BRAKE LIGHTS?

I replaced it with an 8amp fuse and immediately blew it out....which leads me to believe I might have 'other issues'.

ugh.

thoughts?

I'll do the grounding work you suggest....couldn't hurt!

cheers

td

Posted by: Spoke Aug 29 2013, 08:01 PM

QUOTE(sean_v8_914 @ Aug 29 2013, 09:32 AM)

Posted by: tadink Aug 29 2013, 08:08 PM

answering my own questions after a bit of research on this forum -

Which fuse does what?

Left to right, the fuses are numbered.

1 Left high beam

2 Right high beam

3 Left low beam

4 Right low beam

5 Left parking/running lights

6 Right parking/running lights

7 Taillights (including license plate lights)

8 Brake lights, horn, wipers, lighter

9 Power to gauges and G light (charging system), turn signals

10 Fog lights (if fitted)

11 Hazard lights

12 Headlight motors

Fuses 8 and 12 are 25A, the rest are 8A. In later years, they dropped to 16A fuses for 8 and 12, and raised 10 to 16A, too.

Posted by: tadink Sep 1 2013, 03:03 PM

WELL CRAP -

the odyssey continues -

now - I've cleaned the grounds and looked around for wires that seem out of whack or likely to short out (bare, hanging, funky) and now I've blown 2 more 25A brake fuses and managed to get the headlights half up. fuch.

so, back to the original question - what is the best way to check for a dead short? and where to start?

did I mention I hate electrical gremlins?

waaaaahhhhhhh

Posted by: r_towle Sep 1 2013, 03:23 PM

if its your headlight circuit that is the main issue, first, pull the battery and then pull the light switch out with all wires attached.

It will pull down below the dash.
Look at the back and check all the wires...they do melt there, and they can and do touch the dash when the light switch is in the wrong orientation....

If it all checks out, wrap all the way around all the wires and switch with electrical tape and look at how you can make sure it cannot touch the dash when you put it back in place...
IT needs to be turned a certain way.

From there, if its still happening, you need to isolate each circuit.
There are four circuits.
One for each motor, and that is all those circuits do.
Light are a bit more complicated...
High and low beam have there own circuit.
Some of that is shared with parking lights both front and rear, but each circuit is for left and right side of the car....

Typical places to look for issues that I have found.

Headlight motor grounds...near headlight motors.

A pinch in the wiring going to the headlight motors at one of the metal clips that hold the harness to the body.

Side marker lights under the fender.
exposed wires, loose wires under the fender, wires pinched under light housing.

Blinkers.
Same as above.

The list keeps going for all the rear lights also.

BUT
Sounds like you have an issue raising and lowering the lights..
That is a simple circuit from the headlight switch to the motor relays to the motors...
Check it all.

Rich