Ignition Control Unit

I took my mother's car to a specialized workshop today because it's not preheating properly, which means it's very difficult or impossible to start in low temperatures!
The technician there, after a lengthy period of testing, suggested that it might be the glow plug control unit that is installed in the center console.
After speaking with the gentleman, I didn't find him to be very knowledgeable, so I thought I'd ask if anyone here knows anything about it.
The preheating relays activate when supplied with power, all the fuses are working correctly, and the glow plugs themselves are in good condition, but there is no power reaching the glow plugs.
Car data:
Mitsubishi Galant 2.0 TD, manufactured in 1992.

Thank you very much in advance!!!

To me, it sounds like a broken cable. However, since you're using the plural ("the relays"), it would have to be a double break, which seems unlikely.

Since I can't completely follow where there's still voltage and where there isn't, please measure the voltage against ground at the following points while artificially activating the relays:
- Voltage before and after the fuse.
- Voltage before and after the relay (measure and post the readings for all four contacts if possible).
- Voltage at the terminals (as I understand it, 0V).

Regards,
Guste.

Thank you for your quick response.
The cables from the glow plug control unit to the relays are in good condition (they have been measured), and the relays switch when manually energized, but they do not pass any current to the glow plugs (0V). The fuses should be okay. The technician said that the relays are not being activated by this control unit. Unfortunately, I can't say more about it because I'm not familiar enough with the system.

So, does voltage appear across all the glow plugs when you manually apply voltage to the wire between the glow plug control unit and the glow relay?

Then the fault must be located in the glow plug control unit, the temperature sensor, or the wiring associated with them.

At VW, disconnecting the temperature sensor can help with diagnosis. This will cause the system to recognize -40°C and initiate maximum preheating. You could try testing this. However, I don't know if Mitsubishi behaves the same way.

Unfortunately, it's impossible to say anything more specific from a distance without measurements. Also, I'm not aware of any common issues with Mitsubishi vehicles.

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

"Guste" is a German word that means "gust" or "gust of wind." It can also be used as a verb, meaning "to gust" or "to blow."

Here are some examples of how the word "guste" can be used:

* "Der Wind gustete stark." (The wind was gusting strongly.)
* "Ich konnte den Guste spüren." (I could feel the gust of wind.)
* "Der Wind gustete durch die Bäume." (The wind gusted through the trees.)

I hope this helps!