I took my '74 2.0 out for a spin yesterday and immediately noticed that something was wrong. The gas light was constantly lit even though I just filled up the tank. Whenever I depressed the brake pedal, the fuel gauge would move to empty. The voltage is reading low (central console). When driving the car, the tach is about half what it should be. The turn signals don't work (or click). However, the car drives just fine. Could this be a fuse or something more serious?

Damn, this happened to me once too...I can't remember what the fix was...still thinking.

Check the blinker fluid

NO no no! Its the muffler bearings.

Don't use the brakes.

Nice suggestions so far ...

A fuse would just blow...not usually the cause of wonky stuff like that...is your GEN light on? Otherwise could be voltage regulator?

Ok, so I checked my blinker fluid, muffler bearings and, for the life of me, couldn't find the trans ground strap. All no-go. Thanks for all the wonderful and helpful feedback though, gotta love these boards

What is the GEN light? The only light that is on all of the time is the gas light. I'll check the fuses tonight...

You have a ground problem. I would start with the battery ground to body check/contacts clean. Then move to the ground behind the fuse panel. You may need to undo the panel screws. Make sure the battery is disconnected before taking the panel off.

Now I can't tell who is kidding and who is not! This sounds like good advice - Thanks Valy. I will check the grounds.

the trans ground strap was not a joke and also my first thought.

It is above the tranny and ties the engine to the body.
It is usually torn loose the first time the engine is removed by a newb.
It also corrodes and gives a poor ground to the engine electricals.

Stu

Check the connection for the reverse lights on the drives side of the trans. Check all fuses, and roll them in their holders. Check the connections on coil too. Make sure the coil is properly mounted too

No jokes here.

Starting with mine the responses are legit although I don't think I was correct. The GEN light is the generator/alternator light. It's a red light in your combo gauge. Was wondering if it was going bad. When the car gets low on juice it does act very strangely...

The grounding issue is probably it. There IS a transmission ground strap which is about a foot long or so and is a flexible piece of flat mesh-like metal about an inch wide. It's attached to the rear of your trans, then to the underside of the rear trunk. As stugray said it gets ripped off commonly because it looks like someone added it after the fact. If you can't find it, well, that's your problem.

Check the ground strap fuse.

Is it normal here for a newbie to be treated this way? Obviously, this new member is looking for some electrical help and some of us are treating him like you would a freshman in college. It is obvious the brake pedal needs adjustment as it is hitting the gas tank.

Don't think it's possible for the brake pedal to get anywhere near the gas tank and that would not cause the gauges to go nutty and the other issues. It's most likely a grounding problem or a short. If the grounds are OK you'll want to check for a cut in the wiring harness. Voltage regulator is still a possibility but not as likely.

Do the electrical issues only occur when the brakes are applied? Have the turn signals stopped working permanently? When my battery was dying I got a bunch of odd electrical gremlins temporarily. It was a combination of that and the fact that my generator was not quite strong enough to support the needs of the car.

Ok here you go. .What was the last thing that happened just before you noticed the issues. . . did you change anything ??? You said your volt meter reads low. . . . 1st make sure you have a good battery. . 12.5 -13 volts at the battery with the ignition off. . . then check again with the car running. . don't rely on the factory dash voltmeter. .

Easiest way to describe the grounding circuit is to visualize the entire steel body and a huge brown {Ground} wire. . . It ties all the ground circuits together and back to the negative side of the battery. . . Clean the main ground points, but disconnect the battery before starting. . . . they are the battery grd, the trans grd and the ground under the dash above the fuse tray. . there is another ground point above the engine relay panel behind the drivers seat. . . also look at all the connections on the top of the fuse tray at the connection posts , see anything crossed ????

Also above the fuse tray is the main 12 volt common connection, take a look at it but remember it is always hot so it's an absolute must to disconnect the battery unless you want a big flash and fire. . .

Sounds like what is happening is one component has a poor ground, and the voltage for that unit is looking for the best ground it can find back to the battery. . . Because it's designed ground has resistance [poor connection], the voltage is back feeding through other circuits and causing those components to appear they are operating / lighting up with the wandering voltage. .

If that doesn't do it, you might want to do a visual check of the main wiring harness where it runs above the pedal assembly and enters the front of the inside body tunnel. .
I remember a car that the owner drilled down through the panel between the seats to put in a sheet metal screw and went into the wiring harness. . hard to find that issue. .

Does this happen when you first press on the brake? In other words, does the gauge stop working when the brake light comes on or when you press hard on the brake?

First things first. Look at the battery connections. Both of them. Clean them till they are nice and shiny in the holes of the cables and around the terminals. While the cables are off check the battery condition with a battery checker that checks amperage by applying a drain to the battery. Harbor freight has a cheap one that works. With old cars you will need one anyway. Next check the output of the alternator while the motor is running across the battery. It should be around 13.8 to 14 volts. If all this is good then start checking the grounds starting under the car where the ground strap connects to the tranny. Actually like the others said all the grounds need to be cleaned to avoid any more surprises. But also the 12 v connections should also be replugged and checked for looseness or over heating. Old stuff needs a checkup at least every few years especially the parts under the car that are usually neglected. Your car will teach you how to be a better mechanic or encourage you get a better paying job so someone else can deal with it.

The last couple responses are absolutely correct.
One more thing though, o you know which is your warning lamp for charging ? With the ignition on,(engine not running) you should have warning lamps lit for oil pressure, charging and hand brake ( if it's on ) If you don't see the charging light you need to remedy that first.

Thank you everyone for the advice. Last night, I removed and cleaned all of the fuses in the box, then turned the ignition - everything fixed! I guess there was just a weird connection or some corrosion happening.

However, really good advice on checking/taking care of all the grounds. This weekend, I will do this to prevent further complications.

Thanks again!

In addition to the fuses and fuse holder clips, all the ends of the wires going in and out of the fuse box should be attended to.

It's a PITA to do all the under dash stuff (especially if one has a bad back), but well worth the effort.

One of these days I need to swap the OEM fuse box with my Engman fuse box ... I'll clean up all the connectors and wire ends with 'Tarn-X' before making the final connections, then hit them with clear 'Liquid Tape' when I'm done.

Dude you will be amazed by the difference with the Engman kit. 25% brighter interior lights at least. My old one must have been dirty. Or it was out of blinker fluid... (too soon?)

Chris, the above was a joke. Glad he got it fixed.

Ah! See I'm slow... hey we're Laguna Blue brothers I think.

Sorry for the jokes above confusing you.

When you do something that pulls a lot of current (starter, headlights or Brake lights) and something else goes wonky, it is because the circuit that is pulling more current (starter, headlights or brake lights) disturbs the voltage levels that are being measured by other things like fuel level, oil pressure, temps.

I would try to explain, but unless you care about circuit diagrams it would not be worth the effort.
Clean ALL grounds (the one above the tranny is key) and things usually get better.

I spent half my day (at work, on spacecraft) tracking a problem that turned out to be "larger than expected voltage drop in heater power primary" - Pretty much "GROUND PATH CHANGED" since last configuration....
That usually runs about $10,000 per hour of troubleshooting.....;-)

Stu

Thanks Stu. I like a good joke myself, so definitely not a problem I'll be checking all grounds this weekend.

Sometimes.

It give us a better feel for their mechanical/electrical capabilities as well as their general demeanor.

I don't know where to buy muffler bearings these days ...

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but Blinker Fluid is available at JWest Engineering

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