Mass Errors & Electrical Issues: Common Problems

Hello everyone,

Today, it's not a problem with my own car, but with a similar one (a Golf III, 1Z, 3-door).

Here are some of the symptoms (all are common, but not always present):
- If the ignition is off and the brake pedal is pressed, the sunroof briefly activates, the left rear turn signal dimly illuminates, the rear fog light indicator dimly illuminates, the radio briefly turns off, and sometimes the oil light and fuel gauge briefly illuminate.

- When the ignition is turned on, the left rear turn signal bulb flickers, as do the right rear brake light and the fog light indicator. When the brake pedal is pressed, the radio briefly cuts out, and the fog light control lamp glows brighter.

-The window lifters sometimes operate very sluggishly, and the radio then turns off.

- When the engine is running, it behaves the same as when the ignition is turned on. Sometimes, even when the vehicle is stationary, the speedometer flickers briefly and jumps upwards.

Several years ago, this Golf also underwent a complete conversion to the 1Z model, using parts from a car that had been in an accident (including the wiring harness and everything else that goes with it). 'Old' parts from the original car were not used.

Before I end up with gray hair, I'm hoping for a tip. Since the problems are quite varied, I cleaned the cable distribution from the battery to the wiring harness (where 6 terminals connect). This didn't improve anything.

The battery has a good charge, the engine runs smoothly, etc.

I've searched the forum, but I could hardly find anything on this topic. It might be worth checking the relay 109 in relation to this – that's what my research suggests.

Are there any specific areas that are most likely to respond to treatment? Has anyone else experienced this problem before, and if so, how was it resolved?

Best regards, Christian.

Quote:

-if the ignition is off and the brake is pressed, then there is a brief locking activity of the sunroof, the left rear turn signal light dimly glows, and the rear fog light indicator dimly glows,

It probably looks like a mass error related to the taillights at first glance.
That's where I would start my search.
Either there's a faulty ground connection to the body, or there's corrosion damage to the housing of the taillights, which is causing a grounding issue. In this case, the current flows through the remaining filaments of the light, which leads to these symptoms.

Regarding the other issues, you should first make sure that the windows are not mechanically difficult to operate. The ground connections between the dashboard and the body are located on the left (Li) and right (RE) sides of the A-pillar, approximately at the height of the upper door hinges.

Given the recurring similar issue, I suspect a poor ground connection to the chassis. Try creating a solid ground connection from the battery's negative terminal or the engine block (since the engine is running well, it should have a good ground potential) to the chassis (e.g., using a tow hook or trailer hitch). You can use a jumper cable for this, and then re-check the symptoms. (Perhaps something was left behind during the engine replacement...)

Check the ground connection on the left side of the lamp bracket.
Connect a measurement cable from the negative terminal of the battery, and insert a multimeter in between.
connect the power supply to the taillight bulbs.
Then read the value and apply the brake. The voltage drop should not exceed 0.7 volts.