Turn Signal Wiring question

[Farfegnuggin]

I am neck deep into an electrical fight that has caused me to learn WAY more about multi meters, VW relay numbers and auto wiring diagrams than I ever hoped to know. I have had great success following the wiring diagram for my Bug (1971, standard Beetle) and managed to get almost everything working. Except the turn signal 'warning' lamp. Everything works exactly as designed. Emergency flashers flash when switch is activated, turn signals work on both sides with one caveat: once the lamp in the speedo is connected, I get a quick flashing from the circuit. I have the speedo bulb wired into the relay in the same way that the diagram shows. Any thoughts?

[Cusser]

That warning light bulb is OK, right?
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Farfegnuggin]

[Matt Wilson]

It should only quick flash if one of the front or rear turn signal bulbs is missing, burned out, or not connecting.

I had similar issue with the old relay not giving good signal to the KBL terminal. Just connected the blue indicator wire to the 49a instead. As long as the bulbs are making good contact I was good.
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1972 Standard Beetle
1969 Baja Beetle

[ashman40]

What make/model flasher relay are you using? I suspect you are using the wrong flasher relay (generic relay??) or your flasher relay is going bad.


Without the speedo turn indicator lamp, the flasher relays + corner turn signals is very straight forward:

Power from the fuse box (ignition switch power or battery constant power) passes thru the E-Flasher switch and goes to the 49 (+) terminal on the flasher relay. This is how the flasher relay is powered.
Pulsing output from the 49a terminal of the flasher relay passes thru the turn signal switch before going to EITHER the L or R side corner lamp pairs.
When the E-Flasher switch is turned on the power source swaps to battery constant 12v and a path is opened from the 49a terminal of the flasher relay to BOTH the L and R side corner lamps (4-way).
The end result is pulsing power from the flasher relay passes thru two or four 21W corner lamps.

When you add in the turn indicator lamp in the speedo things get complicated. There are two concepts you need to understand:

1) Small wattage bulbs (2W indicator lamp) are very restrictive and only flow a small amount of current.
2W / 12v = 0.167A (speedo bulb)
21W / 12v = 1.75A (corner turn lamp)
If you place a small watt bulb in-line with a larger watt bulb the current flowing thru the smaller bulb will restrict the current flowing thru the larger. While the small bulb may glow brightly, the larger watt bulb may not glow at all even while the current is flowing thru. This means if power flows thru the 2W speedo bulb on the way to ground thru the corner lamps the corner bulbs will not turn ON even if current is flowing because there is insufficient current to light the larger watt bulb.

2) Most think the only way to turn a bulb OFF is to REMOVE voltage. This is just the most common way. Applying the same (or nearly the same) voltage on both sides of a bulb will reduce current flow to zero (or nearly zero).
Consider this: If you run two wires from the battery (+) post and place one wire on each side of the bulb (12v positive current on both sides of the bulb filament) the bulb will NOT light up.
This may seem obvious, but it is a key point... another way to turn OFF a bulb is to apply equal voltage (potential) on both sides of the bulb.
A bulb glows because current is FLOWING thru the bulb... not because of the presence of voltage. The bulb with two 12v+ wires HAS voltage but because the voltage level on both sides of the bulb are the same voltage potential current is NOT flowing. This means it is possible to flash a bulb by:
Maintaining 12v+ on one side of the bulb,
while alternating voltage on one side of the bulb from 1v+ (bright) ~ 12v+ (off).
When the voltage difference (potential) is high more current flows. When the voltage difference is zero... no current flow and the bulb turns OFF.

Ok, so how does this make the turn indicator lamp in the speedo flash??
When you turn the ignition switch ON, the turn indicator lamp in the speedo "sees" 12v+ on both sides of the bulb. The indicator lamp, along with the OIL and GEN lamps are powered by the ignition switch via a black wire from the fuse box.
On the other side of the turn indicator lamp is the flasher relay 49a OUTPUT terminal. While the ignition switch is ON and the E-Flasher switch is OFF there is 12v+ passing thru the flasher relay and looking for a path to ground. With the turn signal switch centered and the E-Flasher switch OFF there is no open path to the corner lamps.
There IS a path to the turn indicator lamp, but the 12v+ coming out of the flasher relay is running head on into the 12v+ coming thru the indicator lamp. No current is flowing thru the indicator lamp so the indicator bulb is OFF.

When you move the turn signal lamp to the L or R turn position:
A path to ground is now open thru the corner lamps on one side. Pulsing current is flowing out the 49a terminal to the corner bulbs. The corner bulbs turn ON. The speedo indicator lamp remains OFF because there is still 12v+ coming out of the 49a is still running into the 12v+ coming out the indicator lamp.

When the flasher relay pulses OFF... no voltage is flowing out the 49a terminal anymore. So the corner lamps turn OFF. But there is still voltage at the speedo indicator lamp. With no positive voltage coming out of 49a to prevent current flow.. current starts to flow thru the indicator lamp and grounds thru the corner lamps. The indicator lamp turns ON! But there is insufficient current flowing thru the small 2W indicator lamp to burn the filaments in the corner lamps so they remain OFF.
When the flasher relay pulses back ON, the corner lamps turn ON and the turn indicator in the speedo turns OFF. While this continues the turn indicator lamp in the speedo flashes OPPOSITE the corner lamps.

Note that when the flasher pulses OFF this is positive voltage from the speedo indicator lamp passing thru the 49a terminal of the flasher relay. This is where some "generic" flasher relays may have trouble. The simple "generic" relays are not designed to handle voltage appearing on the OUTPUT terminals.
This exactly how the VW turn signal system works. The VW compatible flasher relays must sense current flowing OUT of the 49a terminal but not "freak out" if there is current flowing in/past the 49a OUTPUT terminal.
If disconnecting the speedo turn indicator allows the corner lamps to work perfectly (turn or E-Flasher) it is a sign the flasher relay is the problem.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[vdubguru]

Greetings all,
I am running into an issue with my 68 beetle that I think fits this thread. I recently made some modifications to the front suspension and want to give full disclosure. Installed a Limebug 4" Narrowed beam. Did the work myself on the floor of my garage. Installed, driving, all is well.

Problem I now have is, my indicators began to fritz out and I was getting a buzzing/squealing noise from the blue 9 pin flasher box. The dash indicator light stays illuminated and the signals will come on but stay on and the noise happens. Eventually, the noise stopped completely and I figured I needed to replace the blue 9 pin box.

Skip to earlier this week, received the new box in the mail, installed and it still squeals. So I put a voltage tester on it and everything seems to be working except the wire feeding terminal 49a is showing 5-6 Volts. Terminals 30 and 15 both see full 12+ Volts as well as well as the Terminal KBL when ignition is switched on.

Did I get a dodgy new box or should I be looking for something else?

I'm baffled.
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"I wear a suit of armour made only of my mistakes" -unknown

[raydog]

Since you were working with the beam, I would start by making sure you didn't pinch any of the front turn signal wires up under the wheel well. The noise can be from a wire shorting either to ground or shorting to another wire and backfeeding. Eventually, the noise will stop on your new relay too if left like that. A lot of times, odd reading voltages like that are due to poor connections or cross-shorting.
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Come on, It's not rocket science. KISS

[vdubguru]

Thanks, I'll take a look again.
I didn't think anything was binding or touched, but its certainly worth another check.
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"I wear a suit of armour made only of my mistakes" -unknown

[VW_Jimbo]

What happens if you take the flasher out and test it on the battery?
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[ashman40]

My suggestion would be to disconnect the turn indicator lamp in the speedometer. Get both the corner turn signals and E-Flashers (4-way) working normally. Then, reconnect the turn indicator lamp and see if things stop working.

Test the speedometer turn indicator lamp... disconnect the blue/red wire from the KBL terminal of the flasher relay. With the ignition switch in the ON/RUN position, ground the end of the blue/red wire. The center-bottom speedometer indicator lamp should turn ON solid. This confirms the indicator lamp is powered correctly and grounding the end of the blue/red wire will illuminate the lamp.

As a possible workaround, move the blue/red turn indicator lamp wire from the KBL terminal of the flasher relay to the #49a terminal. See if this helps. This is how the later 3-prong flasher relays were wired and can be used as a workaround when the KBL circuit in the flasher relay fails.


Are you possibly running any LED bulbs in any of the corner turn signal light assemblies? VW flasher relays were designed to work with 21W corner lamps. Most modern LED bulbs only draw around 2W and do not put enough of a load on the stock flasher relay. The easiest fix is to add a 50W LED resistor into both the left and right turn signal circuits to simulate two 25W bulbs. This additional load will fool the flasher relay into thinking the proper bulbs are installed.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[vdubguru]

[ashman40]

[Andersonjoe]

Ashman,

I love how analytical you are with the electrical system. Just wanted to say that everything that you've laid out here is super informative and great notes to take for troubleshooting.
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1973 Std. Beetle- Still in restoration. But who are we kidding? When is a beetle ever fully finished?

[PuddleRainbow]