I know this is beating a dead horse and all, but after farting around looking for a tutorial on how to properly do an afterglow system on my car I found things scattered everywhere. So In this and my ensuing posts this weekend I will, cross your fingers, take picks of my install and report back about my findings.

Thermally switched afterglow done right:

What you'll need:
Qty. 1 Five post relay similar to the Metal OEM ones in fuse box (on my 124 anyway) Terminal 30 and 87a must have connectivity un-energized.
10-15 Feet of wire in a decent gauge 14-16 most likely
Wire cutters/strippers
Zip Ties
Heat Shrink Tube
Soldering Iron
Heat Gun

Obviously this should probably be done on a cool engine with it OFF and the battery DISCONNECTED.

1. Locate the thermal switch on the front of the head near the water outlet and cut the wire running to it.
2. Take the two ends and solder and heatshrink wire leads onto it and run the wires to where ever you feel comfortable putting your relay at. (by the fuse box or someplace outside the heat shield would be preferable.
3. Connect these two wires to terminals 85 and 86 of your relay being sure to slide heat shrink over the wire FIRST to protect the terminal after you solder it.
4. Locate the violet wire for the glow plug kill and cut it.
5. Solder and heat shrink new wire on to both cut ends just as you did with the thermal switch.
6. Connect these two wires to terminals 30 and 87A of your relay being sure to slide heat shrink down the wire FIRST to protect the terminal after it is soldered.
7. Zip tie all wire away from any pinch points and hot spots trying best to follow factory routing (they knew what they were doing why mess with it?)
8. Reconnect the battery and glow the plugs once.
9. To test your relay set up disconnect the wire nearest to the thermal switch and tap it to the head of the engine while it is running. If you have done everything properly you should be able to feel the relay click as you tap it.

This setup will only work if your thermal switch is good!! You may need to check proper function of this prior to starting. Your plugs should also be rated for "Afterglow" or the plug life will decrease dramatically. Pictures to follow pending my installation this weekend. One other note, NEVER USE CRIMP TERMINALS EVER when working on the exterior of the car. They get very poor connectivity to begin with and when you add the fact they aren't weather sealed you are just inviting disaster to the party by using them, so DON'T. Best case would be to have a junk Benz harness laying around and cannibalize it by unsoldering the terminals off of it and using them for the relay. Any questions comments or concerns about this please PM me or email me at ShibbyUTman@hotmail.com

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2003 Dodge Ram 2500 Cummins - Georend fully built trans, Banks Big Hoss Bundle, Smarty Tuner, 5" turbo back exhaust. 500 HP and 1100 ft/lbs to the ground.
1979 Mercedes-Benz 300CD - Lost to a four car pile up on 275, Thank You Michigan Drivers.
1986 Mercedes-Benz 300D - Sold, Euro non-turbo car.