My neighbor's '80 300SD has an interesting electrical problem. When he goes to start the car, the glowplug light comes on as normal, he starts the car without a problem. While driving though, sometimes the glowplug light will start flashing then go out. We checked all the wires going to the glowplugs and they were tight. Also, the glowplugs are only about 2 months old. I know from experience with my SD, that a loose glowplug wire caused the light to flash, so that's why we checked for that. Does anyone have any ideas?

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Just because the glow plugs a new, doesn't mean that are good. Why would anyone replace glow plugs (GP) until they burn out. They are like a light bulb, they either work or don't work.

Check the resistance with a digital ohm-meter at the connector of the glow plug cable where it plugs into the GP controller. Pull the cable out of the controller and check in the 5 holes of the connector that connect to the GP. You have to use a digital ohm-meter because the resistance is very low, less than 1 ohm, so a meter type ohm-meter will show 0 ohms on all plugs unless they are open. Replace any plug that shows a difference from the others.

It could also be a intermittent problem in the connector. Plug and unplug the cable several times. This might wipe off any oxide that might between the contacts of the connector halfs.

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