| Author |
Message |
kirk knighton
Samba Member
Joined: January 23, 2005
Posts: 282
Location: Seattle
|
 Posted: Thu Mar 04, 2021 10:04 am Post subject: Brake lights don't work when headlights are on |
 |
|
I've just noticed this. They work fine with the lights off, but with the lights on the brake lights don't turn on.
The twin-filament bulbs are in correctly; with the headlights on it is the smaller, dimmer coil engaged in each bulb. And with the lights off I see the larger brighter coils light up when the brakes are applied.
Strange!
Or is it - strange? |
|
| Back to top |
|
 |
KTPhil 
Samba Member
Joined: April 06, 2006
Posts: 34003
Location: Conejo Valley, CA
|
| Posted: Thu Mar 04, 2021 10:53 am Post subject: Re: Brake lights don't work when headlights are on |
|
|
| Check grounding of the bulb holders and the lamp assemblies. Bad grounds make current seek another path, including through other bulb filaments. |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
|
| Posted: Thu Mar 04, 2021 1:09 pm Post subject: Re: Brake lights don't work when headlights are on |
|
|
I agree.....but also...check the headlight switch function very carefully. There are a couple of 411/412 specific issues.
1. The Bakelite board in the switches of all type 3 and 4 (probably 1 and 2 as well)...gets loose when the switch runs out of lubricant internally on the detent balls.
Its initial symptom is the switch being a little more difficult to pull in and out and feels dry. When this happens...over time the balls and springs inside lever the circuit base plate away from the metal body.
As it gets loose...it can short against the metal of the dash....and this issue is very type 4 specific....and is the 2nd issue.
2. in 411/412...the switches are in deep stamped wells in the metal backing plate of the dash. This is why type 4 headlight and flasher switches have a longer "snout" on the switch end. They have to reach deep into the well in the dash backing plate to make contact with the plate...without bring the switch wires in contact with the metal plate and shorting out.
And...there is an indexing "dent" pressed into the dash metal to correspond to the notch cast into the switch body...to keep the switch from rotating.
The risk....is that if you can wiggle your switch and it feels kind of loose in the dash....the little barrel nut has gotten loose...and the switch can come out of index with that indentation or dent.....and rotate to the side.
On the 411/412....because of the deep metal well around the ends of these switches...and because the headlight switch wire harness is notoriously short....when the switch gets loose....the tension on this short wire harness caused the headlight switch to rotate to the left.
When it does so....it grounds against the side of that deep well behind the dash. At first...it can just short out other items....like maybe brake lights. When it gets loose enough....it will short out hard...and blow the main 16 amp fuse.
You will have no power to ANYTHING in the car ...including emergency flashers.
I learned this the hard way....when my light switch shorted out in 1988...in an un-lit underpass tunnel....in Oklahoma City. I got a fuse and turned on my flashers just seconds before a 20 ton, ten-wheel dumptruck came barreling into the tunnel and just missed me.
You might look at my light switch and flasher switch thread.
https://www.thesamba.com/vw/forum/viewtopic.php?t=658907&highlight=light+switch
Ray |
|
| Back to top |
|
|
kirk knighton
Samba Member
Joined: January 23, 2005
Posts: 282
Location: Seattle
|
| Posted: Thu Mar 04, 2021 6:02 pm Post subject: Re: Brake lights don't work when headlights are on |
|
|
Thanks you guys!
The grounds at the taillights look okay.
I will add that with the lights on and the ignition key turned off after the engine was running the fuel pump continues to run! It shuts off when I turn the lights off. Guessing your points about the headlight switch probably being corroded are spot-on.
Luckily I have a good spare!
Looks like a bit of an upside-down mining expedition to access that switch in the dash? I have pretty poor eyesight and wear progressive lenses in my glasses, making working in close dark tight spaces a challenge. Ah well, that's what Type 4s are all about, no? |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
|
| Posted: Thu Mar 04, 2021 7:11 pm Post subject: Re: Brake lights don't work when headlights are on |
|
|
| kirk knighton wrote: |
Thanks you guys!
The grounds at the taillights look okay.
I will add that with the lights on and the ignition key turned off after the engine was running the fuel pump continues to run! It shuts off when I turn the lights off. Guessing your points about the headlight switch probably being corroded are spot-on.
Luckily I have a good spare!
Looks like a bit of an upside-down mining expedition to access that switch in the dash? I have pretty poor eyesight and wear progressive lenses in my glasses, making working in close dark tight spaces a challenge. Ah well, that's what Type 4s are all about, no? |
Wait.....wait......so.....lights on....ignition key OFF......engine off (or does it continue to run with the key off?).....and.....key OFF....but fuel pump continues to run???
Ok.....your fuel pump relay is mounted (or should be).....on the pedal cluster....just inches from the brake master cylinder and its brake light switches.
Check carsfully down there for loose wires cross connecting. Also check to make sure that you have no brake fluid or washer fluid leaking and getting any of that area wet.....or any of the connector plugs in the steering column.
Ray |
|
| Back to top |
|
|
kirk knighton
Samba Member
Joined: January 23, 2005
Posts: 282
Location: Seattle
|
| Posted: Tue Mar 09, 2021 9:23 am Post subject: Re: Brake lights don't work when headlights are on |
|
|
| raygreenwood wrote: |
| kirk knighton wrote: |
Thanks you guys!
The grounds at the taillights look okay.
I will add that with the lights on and the ignition key turned off after the engine was running the fuel pump continues to run! It shuts off when I turn the lights off. Guessing your points about the headlight switch probably being corroded are spot-on.
Luckily I have a good spare!
Looks like a bit of an upside-down mining expedition to access that switch in the dash? I have pretty poor eyesight and wear progressive lenses in my glasses, making working in close dark tight spaces a challenge. Ah well, that's what Type 4s are all about, no? |
Wait.....wait......so.....lights on....ignition key OFF......engine off (or does it continue to run with the key off?).....and.....key OFF....but fuel pump continues to run???
Ok.....your fuel pump relay is mounted (or should be).....on the pedal cluster....just inches from the brake master cylinder and its brake light switches.
Check carsfully down there for loose wires cross connecting. Also check to make sure that you have no brake fluid or washer fluid leaking and getting any of that area wet.....or any of the connector plugs in the steering column.
Ray |
Hmmm...today I noticed when I press the brakes with the headlights off the brake lights come on AND THE FRONT PARKING LIGHTS also come on! Argh!
Yes, and with foot on brake and lights on I can turn off the engine and even remove the key and the engine continues to run - until I take my foot off the brake.
Check that fuel pump relay? What does it look like? |
|
| Back to top |
|
|
KTPhil
Samba Member
Joined: April 06, 2006
Posts: 34003
Location: Conejo Valley, CA
|
| Posted: Tue Mar 09, 2021 9:47 am Post subject: Re: Brake lights don't work when headlights are on |
|
|
| kirk knighton wrote: |
Hmmm...today I noticed when I press the brakes with the headlights off the brake lights come on AND THE FRONT PARKING LIGHTS also come on! Argh!
Yes, and with foot on brake and lights on I can turn off the engine and even remove the key and the engine continues to run - until I take my foot off the brake.
Check that fuel pump relay? What does it look like? |
Yes, based on your latest symptoms described, I am betting the ignition or headlight switch is miswired or shorted at the dash. |
|
| Back to top |
|
|
Chris Walden
Samba Member
Joined: June 03, 2010
Posts: 147
Location: Indianapolis, Indiana
|
| Posted: Tue Mar 09, 2021 9:03 pm Post subject: Re: Brake lights don't work when headlights are on |
|
|
Like, did all of this just “happen”? I know from experience that grounding issues can cause no small amount of head scratching.
Chris |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
|
| Posted: Wed Mar 10, 2021 8:18 am Post subject: Re: Brake lights don't work when headlights are on |
|
|
The trick is to think about where all of these different functions.....brake lights...head lights....ignition....etc......are actually collectively connected together.
They are not.........kind of.
One could broadly say they are connected together by the grounding system.....the chassis .....and thats true.....but thats not giving them + when the switch or key is turned off.
The point they all have in common.....is the fuze panel and the relay rack underneath it.
The 411/412 fuze panel is a common source of issues. Its why 90% of cars for sale and cars in the junkyard....have their fuse panels hanging loose by tne wires.
In its hidden away spot behind the carpet and metal panel.......the fuse panel is very susceptible to shorting just from having short wires and being crammed into its slot. And...worse.....pretty much all 411/412.....have issues with windshield leakage at the lower corners, leakage and spray through the speedo cable fender well boot and leakage from the through holes from the upper fender bolts.
On every 411/412 I have owned....it leaks down, drips right on the fuse block, corrodes wires and fills the relays up with water
Pull your fuse panel and check it. Ray |
|
| Back to top |
|
|
kirk knighton
Samba Member
Joined: January 23, 2005
Posts: 282
Location: Seattle
|
| Posted: Wed Mar 10, 2021 9:23 am Post subject: Re: Brake lights don't work when headlights are on |
|
|
| raygreenwood wrote: |
The trick is to think about where all of these different functions.....brake lights...head lights....ignition....etc......are actually collectively connected together.
They are not.........kind of.
One could broadly say they are connected together by the grounding system.....the chassis .....and thats true.....but thats not giving them + when the switch or key is turned off.
The point they all have in common.....is the fuze panel and the relay rack underneath it.
The 411/412 fuze panel is a common source of issues. Its why 90% of cars for sale and cars in the junkyard....have their fuse panels hanging loose by tne wires.
In its hidden away spot behind the carpet and metal panel.......the fuse panel is very susceptible to shorting just from having short wires and being crammed into its slot. And...worse.....pretty much all 411/412.....have issues with windshield leakage at the lower corners, leakage and spray through the speedo cable fender well boot and leakage from the through holes from the upper fender bolts.
On every 411/412 I have owned....it leaks down, drips right on the fuse block, corrodes wires and fills the relays up with water
Pull your fuse panel and check it. Ray |
Exactly! Remember I had the non-functioning turn signals issue a month or so ago? I had taken it to the shop for the final fix of my starter issue; they couldn't get to it for several days, and in those several days it sat out in the weather. Which around here is to say RAIN. Steady wet rain.
My cars are always garaged and seldom driven in the rain. Well that revealed the leak in the windshield and the rain filled up the flasher relay.
I had a hell of a time getting the fuse panel pushed up enough to get to the relay, but I did it. In the process however the wires to the relay had pulled out of the fuse panel, and they are so short I couldn't get them back in their respective slots. So I simply plugged the relay into the three wires and it worked!
But did this solution actually cause my current problem?
I haven't had a chance to dig in there yet. Is there a way to get better access to the fuse panel? Can that metal plate be removed? |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
|
| Posted: Wed Mar 10, 2021 10:15 am Post subject: Re: Brake lights don't work when headlights are on |
|
|
| kirk knighton wrote: |
| raygreenwood wrote: |
The trick is to think about where all of these different functions.....brake lights...head lights....ignition....etc......are actually collectively connected together.
They are not.........kind of.
One could broadly say they are connected together by the grounding system.....the chassis .....and thats true.....but thats not giving them + when the switch or key is turned off.
The point they all have in common.....is the fuze panel and the relay rack underneath it.
The 411/412 fuze panel is a common source of issues. Its why 90% of cars for sale and cars in the junkyard....have their fuse panels hanging loose by tne wires.
In its hidden away spot behind the carpet and metal panel.......the fuse panel is very susceptible to shorting just from having short wires and being crammed into its slot. And...worse.....pretty much all 411/412.....have issues with windshield leakage at the lower corners, leakage and spray through the speedo cable fender well boot and leakage from the through holes from the upper fender bolts.
On every 411/412 I have owned....it leaks down, drips right on the fuse block, corrodes wires and fills the relays up with water
Pull your fuse panel and check it. Ray |
Exactly! Remember I had the non-functioning turn signals issue a month or so ago? I had taken it to the shop for the final fix of my starter issue; they couldn't get to it for several days, and in those several days it sat out in the weather. Which around here is to say RAIN. Steady wet rain.
My cars are always garaged and seldom driven in the rain. Well that revealed the leak in the windshield and the rain filled up the flasher relay.
I had a hell of a time getting the fuse panel pushed up enough to get to the relay, but I did it. In the process however the wires to the relay had pulled out of the fuse panel, and they are so short I couldn't get them back in their respective slots. So I simply plugged the relay into the three wires and it worked!
But did this solution actually cause my current problem?
I haven't had a chance to dig in there yet. Is there a way to get better access to the fuse panel? Can that metal plate be removed? |
Yes.....the metal plate can,be removed.......but not without removing the windlace around the door edge which destroys it....and pulling the carpet out. And...without it there is no way to install the fuse panel. It makes more of a mess than it fixes. There are also ducts and hoses behind thst panel.
Once you start excercising the wires attached to the fuse block by taking it in and out.....it gets easier.
Whenever I am removing the fuse panel.....I disconnect the battery always.
Really you move the block vertically until the bottom of the three panel tabs clear and tben you can tilt the top towards you. That helps.
The main relay that usually causes issues with taking the fuse panel out is the flasher relay. Its long....and forces you to lift the fuse panel vertically very high to clear the sheet metal.
What I did.....is I notched the opening that fuse panel sits in.....downward.....just in front of the flasher relay and maybe the headlight relay. I left the metal clip area in the center and about 0.5" at each end so the fuse panel slots in the same way. I worked much better.
I wish it had been in the digital age and I would have pictures.
Another thought I had years ago was making just a short rack for the relays and relocating them.....and making plugs and harnesses from the bottom of the fuse panel to the relays.
Ray |
|
| Back to top |
|
|
Pepperbilly
Samba Member
Joined: April 08, 2017
Posts: 977
Location: Seattle, Wa
|
| Posted: Wed Mar 10, 2021 10:17 am Post subject: Re: Brake lights don't work when headlights are on |
|
|
Hey Kirk,
The carpet has to be pulled /peeled down to get at the fuse block. That exposes the flat metal panel that is attached by several screws. Once the panel is out you can move the fuse block... somewhat limited by the wire bundle of course. Then you will have a clear shot looking at the bottom of the windshield frame. I betcha you will discover where some water leaks are coming from...that left lower corner of the windshield.
Bill |
|
| Back to top |
|
|
|
