electrical issue on the way to work-no turn signal/speedo light

[b15605]

All,

On my way to work this morning (73SB) I remember turning on my turn signals and changing roads. As I was traveling down the road all of a sudden my gas gauge dropped out like it had no power...at that point I thought the gas gauge had failed. A few miles down the road I realized my turn signals no longer work.

When I got to work to do a little looking around I also figured out the generator and oil pressure lights don't come on with the key on/engine off. There are no fuses blown so no help there in tracing it down.

Last clue - the hazard lights work just fine as my initial thoughts were flasher relay.

I am at work with limited troubleshooting tools - is there an easy 'aha' that any of yall would be able to throw out there. Would prefer not to drive home without blinker lights.

[ashman40]

Realize that there is one fuse (#8 ) that powers the E-Flasher (4-way) circuit and a different fuse (#12) for the turn signals... but both circuits power the same single flasher relay. Which fuse ends up powering the flasher relay depends on the E-Flasher switch position. When the E-Flasher switch is OFF, the turn signal fuse (#12) powers the flasher relay. When the E-Flasher switch is ON, the E-Flasher fuse (#8 ) powers the flasher relay. Because of this arrangement, the E-Flasher may work fine while the turn signals do not.

The #12 fuse powers all of the following devices:

Turn signals
Fuel gauge
Three (3) indicator lamps at the bottom of the speedometer
Brake Warning lamp
Seat Belt Warning lamp

These are all the things that stopped working on your car. This suggests your #12 fuse is not powering them. I’m guessing you “looked” at the #12 fuse without removing it. Pull the fuse from the fuse box. Swap it with a known good 8A fuse and retest the things that stopped working. While you have the fuse OUT, take some sandpaper to the contacts at the ends of the fuse as well as the clips that hold it in place. If you want to use a wire brush to clean the contacts I recommend you disconnect the battery and clean all the fuse box contacts as well as the ends of all the fuses to make sure you have good electrical contact.
_________________
AshMan40
---------------------------
'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!}

[b15605]

Spot on as always Ashman...the #12 fuse was indeed blown upon closer observation. I installed a new fuse and it blew immediately so I guess I have a dead short somewhere that I will have to track down...good odds something came loose behind the speedo.

There used to be a good diagram on here showing the speedo wiring and I have a copy of it printed out at home, but can't seem to find it via search this morning...once I have that in hand I should be able to track it down.

Any other short term troubleshooting I can do at lunchtime I am all ears?

[VW_Jimbo]

Remove all of the output side wires from the affected fuse. Then one by one reinstall them. When you hear the “SNAP”, that the wire you need to chase!

Good luck! Hope it is an easy fix!
_________________
Jimbo

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

[Dark Earth]

[ashman40]

When I have a fuse that constantly blows as soon as power is applied... it suggests a direct short to ground that flows more current than the fuse can support. Test the fuse output wires for direct shorts to ground.

Use your digital MM to test each of the fuse OUTPUT wires individually. Set you meter to read resistance and ground one of the probes. Use the other probe to test the wires that were connected to the fuse. Disconnect the wire from the fuse box one at a time and place the probe on the end of the wire. This tests if there is a path to ground on that wire.
Now realize that all circuits eventually go to ground, but very low resistance paths to ground will blow the fuse. An 8A fuse needs at least 1.7ohms of resistance on the circuit. Resistance any lower and the current flow will exceed 8A and the fuse blows. So if you measure any single wire with a resistance to ground lower than 1.7oms, it means the fuse will blow. This tells you that something along that circuit is creating a low resistance path to ground.


Some will argue that you cannot test a circuit while devices (bulbs or motors) are connected. Ideally I see why this is. But sometimes there is a direct short to ground (zero resistance) or a problem that can be measured. Zero resistance to ground should never be the case. So if you test the wires and find one has zero resistance, investigate what is down that path and why you are seeing such a low resistance.
Or look at comparing the resistance down similar paths. For example, measure the resistance to ground for each of the corner turn signal lamp wires where there should be a 21W bulb. If you get three resistance readings of 3.0ohms and one path with 1.8ohms resistance to ground. That may not be enough to right away say there is a short, but why does the one path have much lower resistance... investigate it. We found the wrong bulb installed on a buddy's car by testing the different turn signal lamp paths.
_________________
AshMan40
---------------------------
'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!}

[b15605]

I definitely have a short. There are two wires on the output side of the #12 fuse...a smaller black one and a connector with two green wires going somewhere (? - I assume to the speedo - the wiring diagram shows a green wire going to the emergency flasher switch from #12...does power pass through the flasher switch so that if the switch is off blinker lights work and if flashers on it sources power elsewhere?).

I determined I have a short by blowing a few spare fuses (per VW-Jimbo) as I don't have a VOM here at work...so yep, got it nailed down a circuit, just have to get it home to do the deeper troubleshooting.

Unless anyone else has a magic bullet, I think my best bet is just to drive it home carefully without turn signals and then dive in over the weekend.

[ashman40]

[Starbucket]

You were driving down the road when this happened so look for a spade connector that came off and is grounding, a careful look with a bright light at all the switches, etc.. When you find it give it a good squeeze and reinstall.

[VW_Jimbo]

[b15605]

Wanted to give a followup post for anyone that might read this in the future and wonder about resolution.

First off, wanted to say thanks to all who replied and pointed me in the right direction.

I basically managed to drive home Friday afternoon without blinker lights...not a big deal and traffic was light so got by with it.

Yesterday I decided to take a look into the issue. The first thing I did was trace one of the green wires from #12 fuse and saw it goes to the emergency flasher switch which has already been alluded to by several of the gurus responding to this post. I pulled this green wire off and then installed a new fuse, turned on the key and suddenly no blown fuse, yet the generator and oil light lit up...so here was a scooby clue we were on the right path.

On a hunch I then reinstalled the green wire onto the switch and no blow fuse - the gas gauge came back alive and blinker lights worked, etc. Essentially, things are back to functional. I took it out for a couple of drives and everything worked flawlessly.

That being said, I am not sure if there is something going bad in the hazard light switch and I should begin sourcing a new one? Anything else that could cause this?

Again, thanks to all who replied on Friday and any insight as to the real root cause I would love to hear it as I am sure it may do the same thing again sometime - at least this time I will know where to look first.