Heater core fix; no start

Mk4 Jetta tdi 2003


I just changed out the heater core. Fun job, but I digress. Put all connectors back, save center console outlet. Now no start or instruments.

Have power to cluster (time and mileage only)
Have radio power.
Have flashers and lights.
Have door lights inside and overhead lights.


No buzzer, instruments, or any other dash.


Checked all fuses on drivers side and above battery: all good.


Checked all connections again. Nothing unplugged or missing outlets.


Assistance please. I have an appointment tomorrow and a 500 mile trip Saturday.

Haven't done that job!

Were there any grounds / commons to disconnect in all that?
I'm picturing a bundle having a group of ground wires joined to an eyelet on a body post, which got in your way somehow.

Just a thought, but that type thing would get you a selection of things that have power but no go/light.

Sounds like connector not on squarely.

B3achbum said:

Haven't done that job!

Were there any grounds / commons to disconnect in all that?
I'm picturing a bundle having a group of ground wires joined to an eyelet on a body post, which got in your way somehow.

Just a thought, but that type thing would get you a selection of things that have power but no go/light.

Click to expand...

Cheated. Didn’t even get the main bracket out got the dash loose, but just moved everything with disconnecting only what was in the way: dash cluster, took 13 mm bolts from under steering wheel out so column would be moveable, connectors for vent lights, flashers, rear defroster, stereo out, vent controls, center vent behind stereo cluster, and connectors for the fan and vent module. I disconnected (under the hood) negative cable on battery, ac lines, and coolant lines. In the cab I shifted the dash enough on the passenger side to get to the ac/heater core box. I took out the bolts connecting the cross member to shift it up enough to get clearance for the box to come back a few inches then out through the passenger door along the footwell. Everything in reverse. Hooked up battery. Nothing. Did not take one ground wire loose in the whole ordeal.

csstevej said:

Sounds like connector not on squarely.

Click to expand...

Possible. I will have to take everything apart to see. At least I know how to get it all out now. Should only take a couple of hours.


Question I have is do I need to reset anything with the vagcom after this job?

Sounds like a ground, you didn't see it because it's stuffed up in there somewhere...
I think the one you're looking for is supposed to connect at a 13mm right at the steering column...

Sent from my moto g(7) power using Tapatalk

eddieleephd said:

Sounds like a ground, you didn't see it because it's stuffed up in there somewhere...
I think the one you're looking for is supposed to connect at a 13mm right at the steering column...

Sent from my moto g(7) power using Tapatalk

Click to expand...

That is some great insights. I’ll look there before total disassembly

obstin8 said:

Possible. I will have to take everything apart to see. At least I know how to get it all out now. Should only take a couple of hours.


Question I have is do I need to reset anything with the vagcom after this job?

Click to expand...

Took steering wheel and lower cover off. The pressure from the column dropping put stress on the key harness on the left side. Because I didn’t remove the steering wheel the cover underneath the column covered the view of the connection. Voila, it’s loose. Plugged it in, power. Thanks for the input.


Now the trim pieces go back on.