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Discussion Starter · #1 ·
Hello this is my first post so if it is in the wrong area I am sorry, The problem I am having is I replaced my power brake booster and no matter how much I adjust the cylinder screw that connects to the actual break pedal the brake lights do not go off - They are constantly on - and to top that off my gas gauge goes below the empty line and the turn signals on the dash light up when I turn the ignition on?? All of this started after I changed the power brake booster and reconnected the battery - It was fine before..in addition when I hold the key in a position right before ignition actually takes place(pre starter crank or turn over) the turn signal lights go off and the gas gauge reads correctly....I am very confused - I restored my chevelle years ago but never encountered anything like this and do not really have any one to contact about this - Thank you very much in advance - Aaron
 

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First of all, WELCOME to the BEST site on the net.
Are you sure you didn't pinch some wires during the booster change?
 

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Discussion Starter · #3 ·
Hello and thanks for the welcome - I have looked for any wire that could have been pinched but I cannot find anything - The only thing near the booster is the steel hose that carries the brake fluid and windshield wiper wires - Underneath the dash there are a host of wires but nothing near the hole where the rod of the booster comes through to connect to the brake pedal - Thanks for the response - Aaron
 

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Aaron,
Welcome. You'd get more specific help if you would state what year vehicle you are working on. Why not fix your profile or post to reflect that information (i.e. vehicle type) and let us help you. If it works, consider becoming a member.

Absent of that detail, all I can offer is that you definitely have a short, bad turn signal switch or bad or mis-adjusted brake light switch. The gas gauge problem is indicative of a severe lack of supply to the gauge due to a voltage drain. A fuel gauge is actually a volt meter that displays the votage drop (actuall current flow) in the supply line to the sending unit. If it isn't supplied with the correct voltage it will not indicate properly. That's what I suspect is happening. SOmething is significantly affecting the supply voltage to the gauges in the dash. You are just able to see the indication of this in the fuel gauge. Have you measured the supply voltage in the dash. I'll bet it is real low.

On some vehicles, parts of the dash supply (voltage/current) circuit (especially the Accessory circuit supply)is disconnected when the key is moved from the run to the start position. You may notice the radio goes silent when the key is in the Start position on some vehicles. This assures maximum flow of the battery supply to the starter. That's perhaps why things change when you move the key. You are between the run and starter contacts of the ignition switch and disconnecting what ever part of the system that is "dragging" the supply voltage down, thereby allowing the fuel gauge to get the full 12 volts and read normal. Again, this would indicate an abnormal current drain when in the "run" position. That's why we suspect shorted wires or a bad turn signal or brake light switch. (Also, if your car has a BRAKE idiot light, unplug the sensor wire from the switch under the hood to eliminate that as a cause.)

Disconnect the brake light switch wires from the switch. Do the brake lights stay on? If so, look for a shorted wire(s)in the turn signal harness or a bad turn signal switch. The brake and turn signals use the same circuit and bulb filaments. A bad turn signal switch, flashers or harness could actually light both brake light bulbs leading you to think the brake switch is the cause when if fact it's the turn signal circuit that's bad. You may be working in the wrong area of problem. by disconnecting the brake light switch wires, the brake pedal is no longer a factor no matter how it is adjusted. If the problem remains, stop adjusting the brake pedal.

Did you do anything else to car at that time or around when you did this job?
 

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Discussion Starter · #5 ·
Hello Herb -
First off my car is a 1972 Chevelle Malibu Coupe 350 V8 - During the time I was swapping out my Power Brake Booster I did not change anything else - It was just sitting in my garage for a couple weeks and earlier in the day I started it and moved it outside to clean my garage floor - I disconnected the battery because I figured the brake lights would come on while I was changing the booster - when I finished installing the new booster I hooked the battery up and tried adjusting the pedal - No luck and when I tried starting it to see if I at least foxed the brakes I noticed all the lights acting fishy - I will check everything you suggested, ugh I hope it works - many thanks to all responses - Aaron
 

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Discussion Starter · #6 ·
Just an update - the brake light prob was fixed - I had a bad brake switch but the gas gauge still does not read correctly and the turn signal lights in the car along with all the other lights on the dash stay lit up - ??? Anyway thanks to all for the help - Aaron
 

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Discussion Starter · #8 ·
Hello -
Yes I have all the bulbs are good (work) - when you say emergency brake flasher do you mean the hazard light flasher or the emergency brake light on the dash? Thanks again to everyones help - Aaron
 

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I would check or replace the flasher(s). Don't remember if there are on or two on that year. If one or both are shorted or the contacts are welded together by now, that could cause the problem with the indicator lights. Glad you found the switch problem.

Again, I think the gas gauge problem is an idication of a voltage drain or other problem. First and foremost, make sure the flasher(s) is good. What is the answer to the following:

- Are the dash turn signal indicator lights lit when the key is off? This would indicate a bad hazard flasher or circuit (possibly a switch).

- Is the battery fully charged?

- Do the lights go out after the car is started?

- What happens when the hazard flashers are activated? Can you hear the flasher clicking under the dash? Do the tail lights flash.

- Do the turn signals work (flash independently of each other)?

Sure sounds like a bad flasher device or switch.

Let us know the answers and we'll go from there.
 

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Discussion Starter · #10 ·
Herb,

The dash indicator lights are off when the key is in the off position,

The battery is only a month old and good,

The dash lights stay on after the car is started and running and when I turn on the interior light everything goes to normal....

I saw a guy on Ebay who has a color copy and color key of the wiring diagram, I may buy that from him for 19.95 buy it now and start checking wires - Thanks Again Aaron
 

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Man Aaron, that's a wierd one. You are definitely getting a voltage back-fed to the dash light system.

I'm not familiar enough with the spicific wiring of the 72 to help much withtout a diagram, meter and the car in front of me. However, keep a couple of things in mind as you go through this process:

- Don't ASSUME!!!! just because your battery is new doesn't mean it's good. Or, just because you think the bulbs or flashers are good, doesn't mean they are. Check everything!!!!!!

- There's nothing to say a mouse didn't climb up inside the dash and eat through some insulation causing a short. Sounds crazy, but that actually happens. I parked a car in the driveway one evening, next morning things didn't work right. Mice are a major hazard after collision and rust to cars. Again, don't assume this didn't happen, verify things are still "in one piece".

- Try pulling fuses, with the key on, to try to determine which circuit could be causing the problem. Don't stop after the first time you pull a fuse and the symptoms change. Replace that fuse and continue pulling others to see if more than one circuit is effected.

Keep us posted on what you are doing and the results. We all want to learn from this one, I'm sure.

P.S. Consider moving future postings to the electrical part fo this site.

 

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I'm doing brake work on the '67 right now, and have come to the part where I'm adding the booster. It made me realize there are a LOT of wires running around in that area. Have you checked the wiring under the hood to make sure that two haven't shorted together?

I had a very odd voltage leak problem once and it turned out one of the wires in the firewall block had overheated and melted the connector, so that two wires were touching, feeding power to the right side turn signal. I would look at your fuses and connections around the fuse block.

Get the car running with its electrical wackiness doing its thing. Then pull fuses (like dash lights or whatever) one at a time and see if they affect anything. If it changes or stops that will give you an idea of where the problem may be in the circuit.
 
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