Keep blowing fuse 34

Hello all. My 2001 Jetta alh keeps blowing this fuse. It started and ran fine three weeks ago when the temperature was around -8c. The next day, it was -27c. I started it and it ran like crap. Got the codes associated with this fuse blowing. I parked the car until the weather warmed up.
This weekend, I replaced the starter. It was giving me problems anyway, so it wasn't a waste of time. It is still blowing the fuse. It blows when I turn the key to on, before I try to start it. I took out the battery, cleaned all the grounds I could find. No progress. I have tried both a 10amp and a 15 amp fuse.
Any suggestions on where to look next..?
Hopeful for some ideas.

Thanks, Debbie

Throw in a 30 amp fuse and look for the smoke.

JUST KIDDING!!!

Does it blow the fuse immediately or do you have to drive it for awhile? I don't have a wiring diagram in front of me but you need to find all of the things on that circuit and start unplugging them. Your best bet is a circuit breaker that you can put in place of the fuse while you do troubleshooting. Another option is a multimeter with a beep for checking continuity. Connect it to the load side of the fuse socket and ground. If it's beeping, you have a consistent short to ground. This is helpful in troubleshooting. Now wiggle wires and listen to the beeping. Hopefully you wiggle something and the beeping stops. This tells you a general location of the short. Now start isolating that area until you have it narrowed down to as small as area as possible. If you can't get the beeping to stop either you have tinitus or you need to start unplugging things on the circuit.

You also need to inspect the wiring carefully. Be warned that often the loom can look perfect but the loom has worn away the insulation on the wires.

Good luck and let us know what you find.

Haha. If I threw a 30 amp in, I would walk away and watch it burn. ����
Yes, it blows right as soon as you turn the key to on. We put a 15amp circuit breaker in and no joy. It gets really hot. I will start checking the harness towards the backside-egr. It is very oily back there from it leaking. Maybe the n239 shorted out.
Thanks for the quick reply.

Debbie

A continuity test would indicate the devices in the circuit.
If a wire was pinched, frayed or such and grounded the circuit breaker will give pulses of power and may damage the wire, possibly other wires in its harness.

A quick check it looks like the fuse powers at least the EGR solenoid, MAF sensor, ASV, N75, and cold start valve. (possibly more)
Its a yellow/black wire.
I would unplug all of those and see if the circuit still has continuity with an ohm meter.
Start looking at the wire harnesses from those controls for damage.

Great idea. I will try that. Unplug those things. Plug them back in one at a time.

Thanks, Debbie

The anti-shudder valve vacuum solenoid harness wires are very prone to getting chafed insulation. It is the last stretch in the harness that runs along the top of the firewall towards the passenger side.
Pull them out of the corrugated loom between the harness connector and where they branch off from the rest of the harness.

sportsmartcar said:

Great idea. I will try that. Unplug those things. Plug them back in one at a time.

Thanks, Debbie

Click to expand...

I'm thinking with everything unplugged you may see the short and confirm its a wire issue as JETaah indicated.

If with all those unplugged you loose the short you could wiggle the wires to see if it reappears.
If not then the components 1 at a time.
If you have an multi meter a resistance test on the components to check for low resistance. Maybe less then 20 ohms

I have a small clamp on amp meter I use to use for tracing shorts in wire harnesses. (about 3 inch (US) square.
I used an old directional light and flasher to pulse power through the circuit.
The bulb limited the power to prevent wire damage.

Almost surely a wire is shorting.

Thanks everyone I have an egr delete kit coming. I will have a look at all the wiring when I install that.

Thanks, Debbie

So upon further inspection today, I found the wires to the plug that goes to the ccv heater frayed. Is it ok to leave this unplugged until I can get one from the junkyard and splice it in?



Thanks, Debbie

This is probably the worst time of year to do so. Can you just tape it up and keep the wires apart from one another?

No kidding. Nothing ever breaks in +20c weather, right? I took it for a drive of 100km today. No issues with it unplugged. But I will seperate and wrap each wire to prevent more moisture from entering the plug. Next time I am at pick n pull, I will grab a plug.

Thanks, Debbie

Unless I missed something from my notes.

Relay 109 to:

Fuse 34 > to splice A100 (internal of the wiring harness)
A100 > to T6/5 (brown connector) to splice E29 (internal of the wiring harness)
E29 > to G70 (MAF), N75 (vac control for the Turbo Actuator), N18 (EGR vac regulator), N239 (ASV), and J370 (GP relay)
A100> to 14/6 to N108 (cold start injector [inside IP])

N79 (Positive Crankcase Ventilation Heating Element) is not associated with Fuse 34.

Uh oh. Lol. I guess I will start looking for more chafing wires.

Thanks,Debbie

I wonder whether the 109 relay be shorting internally. Anything electrical stuff added recently? (often one is poking up in that neighborhood to pull power from and that's a good opportunity to introduce a problem)

Check fuse connection on top of battery.

UhOh said:

I wonder whether the 109 relay be shorting internally. Anything electrical stuff added recently? (often one is poking up in that neighborhood to pull power from and that's a good opportunity to introduce a problem)

Check fuse connection on top of battery.

Click to expand...

Already checked and cleaned all grounds. Fuses on top of battery are good to excellent. I will pu a relay 109 in case it does it again. 400 km so far, and no trouble. I left it unplugged. I will pick up an end at the pickers and splice it on the weekend. My EGR delete kit arrived today.

Thanks, Debbie

UhOh said:

I wonder whether the 109 relay be shorting internally. Anything electrical stuff added recently? (often one is poking up in that neighborhood to pull power from and that's a good opportunity to introduce a problem)

Check fuse connection on top of battery.

Click to expand...

Would be easy to check with an ohm meter.
Unplugging all the devices might stop the fuse blowing.
If it still blows it could be wires shorted.

You say you car runs fine with fuse #34 unplugged? Are you sure? Have you checked the timing on your injection pump? If/when fuse #34 is removed or disconnected your static timing in VCDS should jump to 255 and stay there. You might want to unplug your IP and make sure that the cold start injection valve has not shorted out internally. Does this idea help?

It ran like crap with the fuse blown. It's fixed. The n239 valve shorted out because of the oil splash from the egr. Egr delete kit installed. I left it unplugged. 2 thousand km later and no problems.

Thanks for all the trouble shooting.
Debbie

sportsmartcar said:

Maybe the n239 shorted out.


Debbie

Click to expand...

You had the answer all along.

I still appreciate all the help.
Thanks, Debbie