Glow Plug Light: Troubleshooting & Repair

"I'm having an electrical problem with my Passat 35i, 1.9 TDI 1Z. The battery keeps draining. I've noticed that the yellow preheating lamp doesn't turn off completely; it stays on dimly in the background. You can almost only see it in the dark, but it's there."

Also, apparently all four glow plugs burned out recently.

Okay, so here's the question: Has anyone ever experienced something like this before? And can it be traced back to a specific cable? It sounds almost like a short circuit or leakage current to ground.

hello

It's best to start by using an ammeter and pulling out each fuse one by one, observing when the current draw drops to near zero. Glow plugs can sometimes fail, especially with high mileage (including all of them). Personally, I suspect you have a grounding issue. Have fun troubleshooting!

Best regards.

'hb'

If the preheating time for the vehicle is still controlled by a relay, I would replace it.
I had a similar problem with my Polo. The relay got 'stuck' due to wear and tear, causing the glow plugs to be constantly energized. As a result, the glow plugs wore out and the battery drained.

Tip: Don't buy the relay from VW (they overcharge), but from an auto parts store, for example, a Bosch service center. It will only cost about half as much there, and you might even be able to choose between different bulb lengths.

Hi Derby,

I'm sorry, but what you're writing isn't entirely correct.

The glow plug and the spark plugs are controlled by the engine control unit (ECU).
Sure, the candles are switched on by a relay, but the lamp is definitely NOT powered by a relay, but directly by the engine control unit. So, nothing can get stuck.
Therefore, the lamp can also blink during the "initial setup," and it does so even in emergency mode!

However, your description matches the old swirl chamber diesel engines.

m;