MoparFins

Please login or register.

Login with username, password and session length
Advanced search  

News:

We changed servers, which is good, and lost all passwords, which is bad. See above.

Pages: [1] 2 3 4   Go Down

Author Topic: Serious Brake Circuit Problem  (Read 1947 times)

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« on: May 02, 2009, 05:06:36 AM »


Hi everyone,

Last night My friend Jon and I were working on my 1968 Sport Fury. The good news is that she now has 4 new shock absorbers. The bad news is that there is something wrong in the brake electrical circuit. We took the car around the block and every time I touched the brake pedal the headlights would flick off for a second and the dash lights would dim. The problem got worse as I headed home. It got to the point where if I put the turn signal on and hit the brakes, I'd lose the headlights completely and the blinker wouldn't even blink!!!!

Got it back to the barn and started to investigate. When I would step on the brake pedal, the dash lights would dim significantly and the ammeter needle drops from straight up to halfway to the first line on the Discharge side. I could actually hear a brief change in the motor when the pedal is pressed.

Jon disconnected all the bulkhead connectors, cleaned all the contacts as best he could and reconnected everything. Went to start the engine, it turned over a couple times and then lost everything electrical. Total absence of voltage in the car. ARRGH!

Got out the FSM (without a doubt the best money I've spent for this car) and started tracing out the electrical circuit. Working backwards from the battery, we checked the fusible link and that was OK. From there it goes to the Ammeter thru the bulkhead connector. We removed the appropriate connector and noticed that the contact for the fusible link/ammeter looked a little charred. Not a good sign.

Jon got under the dash to see what was going on there. He doesn't know what he did, but after moving some unidentified wires all of a sudden we had voltage again. We started the car and to no surprise, we had the same problems as before, except that the headlights no longer flicker when the pedal is applied. Jon started to measure voltages under the hood. The Battery remains rock steady at about 14.3V regardless of the brake pedal. However the feed side of the ballast resistor (to the battery), drops from 12.3V to about 8V when the pedal is pressed!

IMPORTANT NOTE: As I mentioned in an old post from last year, we had to modify the ignition circuit because after converting to electronic ignition, the engine wanted to die when the brake pedal was pressed. We provide +VBAT to the ECM directly from the battery using a switched relay. That solved the engine symptom, but obviously did not address the cause of the problem:Low Voltage.

Anyone have any ideas? Can the ammeter become a high-current draw itself? I'm out of ideas and I'm confident that when this problem is solved, I can return the ignition circuit to it's normal circuitry. I think the problem is going to found behind the dashboard. I'm not looking forward to removing the instrument panel, but if I have to.....

As always, any help or suggestion is sincerely appreciated.

Thank you,
Uncle Hulka
Uncle Hulka2009-05-02 10:08:22
Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Stan Paralikis

  • Hero Member
  • *****
  • Karma: +0/-0
  • Posts: 114897
    • View Profile
Serious Brake Circuit Problem
« Reply #1 on: May 02, 2009, 09:14:12 AM »

Plain & simple UncaHulk... SHORT!  And a big one.
I'm waaaay better at tracking down shorts than in trying to explain how to but.....
 
You activate brake light circuit, headlight circuit go screwey.
In's in those two circuits.  Don't go blaming anything else or you'll lose track.
I'd start by y running a new temporary brake light circuit completely independant.
If everything's hunky-dory, then that's the problem.
 
And so on...

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« Reply #2 on: May 02, 2009, 09:52:13 AM »

Copy that, Commando. And thanks for the reply!!! I figured it was a short of some kind. I just wasn't sure if this wasn't a symptom of a familiar mopar-related issue.

In trying to figure this out by reading other posts, I came across CBarge's "MAd Wiring" article about bypassing the Ammeter and bulkhead connection. Do you or anyone else have thoughts on this.

As soon as time allows, I'll try your suggestion, Commando. Thanks again!

Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« Reply #3 on: May 02, 2009, 01:47:09 PM »

*****   UPDATE   *****

Had to move the Fury a bit today and noticed that the ammeter needle now moves up to the first line towards the Charge side when the engine revs are increased (1,500 RPM approx). This is a new condition.

Could this be because we cleaned the bulkhead connections?


Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Leaburn Patey

  • Hero Member
  • *****
  • Karma: +0/-0
  • Posts: 4606
    • View Profile
Serious Brake Circuit Problem
« Reply #4 on: May 02, 2009, 03:25:04 PM »

I would suspect the headlamp switch.
Why?
Power going to the brake light switch is fed by the headlamp switch. 
Another trouble spot can be the turn signal switch.
And last spot to check is the dash light dimmer switch.Which is more common to fail and it is also fed by the headlamp switch.
Between the three of them,if there is a bad ground,juice will find a source to feed from causing a draw and short.
Double check the ground wire for the headlights.It is usually bolted to the rad core support.If it is rusty,clean 'er up.
Check ground strap at steering column.
 
Now,as for the ammeter guage,yes,after cleaning the bulkhead it now works like it should-based on your description.
Yes,the ammeter guage itself does draw a lot of power and is famous for turning drivers into pedestrians.
Do the MAd conversion or just add a wire with a fusible link between the BATT stud of the alternator to the BATT stud of the starter relay.Done in 10 minutes,cheap and no more dash meltdowns.  
Why?
CBarge2009-05-02 21:00:48
Logged
1968 Newport Custom project BOAB
1973 Satelitte wagon
1983 Dodge 400
2006 300C HEMI!!

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« Reply #5 on: May 02, 2009, 04:14:55 PM »

CBarge,
You ROCK!!!!

BTW, I loved the video clips! I'm still not clear on the entire procedure, but I'll get it.

Thank you!
Your ol' Uncle Hulka


Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Steve

  • Administrator
  • Hero Member
  • *****
  • Karma: +1/-0
  • Posts: 8653
    • View Profile
Serious Brake Circuit Problem
« Reply #6 on: May 02, 2009, 05:15:30 PM »

Woah you bunch of rocket scientists  
 
You guys missed some points.
 
Step on brake, lights go out  (Stop Lights are fused)
Headlights have a circuit breaker
Release the brake they come back on.
Jon moved wires under the dash and things changed. . .
 
It's simple.  The brake pedel is rubbing against the harness under the dash.  It's probably hitting the return wire to the battery from the ammeter.
 
Hulk. . You have a potential fire on your hands.  Disconnect the battery and get under there again and look.
Logged
Favorite Expression. . . Damned Kids.  Lots of projects.  Donations accepted

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« Reply #7 on: May 03, 2009, 02:55:42 AM »


Great advice, Polaraco, and I appreciate it! Makes perfect sense.

But......

That was actually my first thought that night. A mechanical cause to the problem. Jon looked around under there and didn't see any areas of contact. Additionally (again, if memory serves) I thought he disconnected the brake switch and the problem stopped. I could be wrong about this. We tried so many different things that night it's tough to remember.

I'll talk to Jon today (if not tomorrow at work) and rehash everything we tried and their results.

Regardless, I will disconnect the battery this morning.

Thank you all for your help and advice. CBarge, I think I am going to perform your improvements as well, but not today. The Honey-Do list is getting pretty fearsome! ;)



Uncle Hulka2009-05-03 10:53:47
Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« Reply #8 on: May 03, 2009, 05:57:52 AM »

*****   UPDATE   *****

Just got off the phone with Jon and he confirmed that when we unplugged the brake switch, the drain stopped.


Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Leaburn Patey

  • Hero Member
  • *****
  • Karma: +0/-0
  • Posts: 4606
    • View Profile
Serious Brake Circuit Problem
« Reply #9 on: May 03, 2009, 06:41:14 AM »

So,in theory the brake light switch is feeding off something else.
Look at the FSM,it shows the brake light switch is hot from the headlight switch.
BTW,just remembered..Check all the bulb sockets in the taillights.They provide ground to BOTH the brake and turn signal light bulbs. 
I do not mean to send you all over the car but I am tyring to rule out all possiblities.
 
Logged
1968 Newport Custom project BOAB
1973 Satelitte wagon
1983 Dodge 400
2006 300C HEMI!!

Steve

  • Administrator
  • Hero Member
  • *****
  • Karma: +1/-0
  • Posts: 8653
    • View Profile
Serious Brake Circuit Problem
« Reply #10 on: May 03, 2009, 06:49:19 AM »

Then there has to be a serious short in the brake lights and it's being fed after the fuse.
 
The brake lights don't get fed through the head light system.  The fuse should be blowing unless you have a monster in  there.  The fact that things improved when he moved wireing around is a clue.
 
Tell you what. . . Take the tail light bulbs out., all of them and see what happens.
Logged
Favorite Expression. . . Damned Kids.  Lots of projects.  Donations accepted

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« Reply #11 on: May 03, 2009, 08:43:24 AM »

Great insight, guys. I would've thought a drain this severe would've popped a fuse.

I will remove the bulbs one at a time and note any changes. Sadly, can't do it today.

This is a puzzler. Also why I dread electrical problems like this. You can get dragged into any place in the car to track down the cause. For me it's worse, because I don't fit under my dash too well.

I know I'll be pulling the instrument panel out soon. Hope that's not too big of a job. The FSM documents it pretty thoroughly, but you never know. A good time to replace the AM radio with a correct AM/FM I picked up last year. I have an AM/8-track, but it needs a belt and I haven't found one yet.


Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Stan Paralikis

  • Hero Member
  • *****
  • Karma: +0/-0
  • Posts: 114897
    • View Profile
Serious Brake Circuit Problem
« Reply #12 on: May 03, 2009, 08:52:43 AM »

[/QUOTE]
Large O-ring from a plumbing supply house

Steve

  • Full Member
  • ***
  • Karma: +0/-0
  • Posts: 176
    • View Profile
Serious Brake Circuit Problem
« Reply #13 on: May 03, 2009, 09:07:54 AM »


Great idea, but it's supposed to be a flat belt (there's no groove on the flywheel to keep it in place). Do you think this might still work?
Uncle Hulka2009-05-03 14:28:31
Logged
Uncle Hulka

1967 Oldsmobile 4-4-2
1968 Plymouth Sport Fury Conv w/Factory 440HP
1969 Oldsmobile Cutlass S
1969 Oldsmobile Delta 88 w/Original B07 Police Package
1970 Chevelle 396

Steve

  • Administrator
  • Hero Member
  • *****
  • Karma: +1/-0
  • Posts: 8653
    • View Profile
Serious Brake Circuit Problem
« Reply #14 on: May 03, 2009, 10:09:29 AM »

Quote from: CBarge
So,in theory the brake light switch is feeding off something else.
Look at the FSM,it shows the brake light switch is hot from the headlight switch.
BTW,just remembered..Check all the bulb sockets in the taillights.They provide ground to BOTH the brake and turn signal light bulbs. 
I do not mean to send you all over the car but I am tyring to rule out all possiblities.
 
True, but that's external of the switch.  The only other place it can be is in the turn signal switch.  But that would pop fuses.  Remember the brakes lights go through the signal switch.  But that doesn't make any sense either.  The turn signals work.  The ignition doesn't run up there and the column isn't lit by the head light switch.  It sounds like a dead short from wires rubbing more than anything.  Remember, the headlights have a cirsuit breaker so they would recover where a brakes lights would just blow a fuse.  Something is tugging on something somewhere.  It's the heavy discharge that is the kicker.  Even bad grounds won't do that.
 
 
POLARACO2009-05-03 15:10:35
Logged
Favorite Expression. . . Damned Kids.  Lots of projects.  Donations accepted
Pages: [1] 2 3 4   Go Up
 

© 2008-2014 Steve Hobby • © 2015 Allpar, LLC