Golf TDI Glow Plugs: 1994 Model

Hello, I'm new here and find the forum very well done and very informative. Now, I have a small question: Is it possible to check if the glow plugs are functioning correctly? By measuring the current or resistance? Or should I definitely replace them at 180,000 km? I just built a VAG-Com adapter with an RS232 (MAX232) receiver. If anyone is interested, please feel free to contact me. It works very well with my '94 Golf using the VAG demo software. Thank you in advance for any answers.

Regards,
Maik Engelberth.

Hi,

The glow plugs in TDI engines are not critical! So, only replace them if they are defective.

You can measure them with any multimeter or even with a test lamp.

Measuring the total current is certainly the most complex method!

Hi,
Thank you for the quick response. So, am I correct in understanding that the glow plug either has continuity (I'm guessing less than 5 ohms) or no continuity, and if it doesn't have continuity, it's defective?

Regards,
Maik Engelberth.

Correct it's that simple (usually).

maik Engelberth wrote:

I just built a VAG-Com adapter with an RS232 (MAX232) receiver. If anyone is interested, feel free to contact me. It works very well with my '94 Golf and the VAG demo software.

Hi Maik,

If you could email Rainer the schematic diagram of your adapter, he might (perhaps?) include it in the VAGCOM technical article with your permission.

Then, any interested party could refer to it.

Could someone please post the resistance value of a new light bulb?

Preferably, from the long glow sticks of AFN?

Hi,

Varianti wrote:

Could someone please post the resistance value of a new glow plug? Preferably, from the long glow sticks of AFN?

It's not a useful criterion in my opinion because it's unreliable.
Simply use a standard 55W incandescent light bulb for a continuity test, and you're done.

Best regards, Rainer.

Rainer K. wrote:

... It's not a useful criterion in my opinion because it's unreliable. Simply use a standard 55W incandescent light bulb for a continuity test, and you're done. ...

Sure, here is the translation of the text from German to English:

"Hi varianti,"

This phrase is a greeting in German. It can be translated as "Hello varianti" or "Hi varianti."

I think Rainer is right, but you can easily calculate that yourself.

The light bulbs are rated at a power of 150W each. This means approximately 12A at 12V (which is actually 144W!).

So, R = U/I = 12V / 12A = 1 Ohm.

Hi,
It's not quite that simple: The resistance, and therefore the current draw, of the glow plugs depends on the temperature of the heating element. Nowadays, a combination of a heating element and a control element is used to safely limit the temperature. The control element consists of a material with an exceptionally high temperature coefficient.
The power rating of 150W likely does not refer to the cold state, but rather to the power output after a few seconds of warming up.
The resistance would then be less than 1 ohm.

Best regards, Christian.

Hi,
The cold resistance of four Beru 0 100 221 165 11V spark plugs (freshly unpacked) is between 0.55 and 0.58 ohms.

Best regards, Rudi.

christians wrote:

... The power rating of 150W likely does not refer to the cold state, but rather to the power output after a few seconds of warming up. The resistance would then be less than 1 ohm. ...

"...that's correct, which is why I also don't think it makes sense to specify a resistance value."

Hi,


...that is correct, therefore I also don't think it makes sense to specify a resistance value.

I completely agree. That value is only useful for testing the glow plug for a short circuit.
The values cannot be easily measured with a standard multimeter because they are in the range of the contact resistances of the measurement cables. I increased the voltage on a laboratory power supply until 1A was flowing and simultaneously measured the voltage across the resistor.

Best regards, Rudi.

The easiest and safest way is with a test lamp (with a 55W headlight bulb, about 5A will flow). You can immediately see what's happening! If the light illuminates, everything is okay; otherwise, .

joergs wrote:

The easiest and safest way is with a test lamp (with a 55W headlight bulb, about 5A will flow). You can immediately see what's happening! If the light comes on, everything is okay. Otherwise,

Hi.

This measurement does not guarantee that the candle is intact.
If there is a partial defect in some (admittedly rare) component, for example with a resistance of 3 ohms, the test lamp will light up as usual, but the heater will only provide a fraction of its normal heating power.

When placed in series with a standard headlight bulb, a resistance of 3 ohms is clearly noticeable --> the bulb only glows weakly.

Sorry, I think I was unclear! By 'prüflampe' or 'lämplein,' I meant a genuine, fully-grown headlight bulb! Okay?

joergs wrote:

Sorry, I think I was unclear! I meant a genuine, fully-grown headlight bulb! Okay?

Okay.

The "Lämplein" looked like a test light again...