123 Chassis Early 240D 4 Cyl Glow Relay Manual Override Kit w/ Upgrade Plugs

Fits 1977 to 1979 4 Cylinder 240D with series glow plugs - with PDF Digital Instructions!


123 Chassis Early 240D 4 Cyl Glow Relay Manual Override Kit w/ Upgrade Plugs
Free Add-Ons Included:

Fast Glow Plug and Push-Button Relay Upgrade 1961 to 1979 Installation Instructions by Kent Bergsma - Download

Product Details

If you are tired of glow plug problems on your old diesel, then this kit is made for you. How would you like to start your early 123 240D diesel in 10 to 15 seconds? How would you like to be able to still start your car with one or two glow plugs burned out? How would you like to be able to control when and how long your glow plugs stay on?

Maybe you have had the experience of glow-cycling your engine two or three times on those cold winter mornings or worse yet, maybe you have had the misfortune on 123 models of having your glow relay staying and not shutting off. If that happens you will have a dead battery for sure and maybe burn out your glow plugs too. When installed, our kit will give the advantage of modern pencil style fast glow plugs and total manual control of your glow ignition system.

The key to the conversion is replacing your fragile series loop style glow plugs with pencil parallel (upgraded) large thread plugs and installing a manual control relay to light these new plugs (powered by a dash mounted switch). Your glow plug sensor will not work with the conversion kit and is left disconnected. You DO NOT use a ground wire with the fast glow plugs or you will burn them out. When you push this switch with your left hand the glow plugs will come on. When you release the switch the glow plugs will turn off. YOU decide how long to glow cycle depending on outside temperature and temperature of the engine. You can even hold the button down for 20 to 30 seconds after the engine fires up for smoother starts and less smoke.

The complete conversion kit includes the following

  •  Heavy Duty Manual Relay
  • Quality push button hole mount switch
  • Mercedes factory 80 amp fuse holder
  •  2 - 80 amp strip fuses
  •  Correct size and length of wire needed
  •  All terminal connectors required
  • 4 Upgraded Pencil type Fast Glow Plugs
  •  Three New Glow Plug Wires
  •  Complete step-by-step PDF downloadable instructions 

ALREADY HAVE THE GLOW PLUGS? If you already have the fast pencil glow plugs and connecting wires you can order the installation kit with instructions by itself. Please see related products below:


How to view the PDF digital instructions:

Once you complete the purchase of this product you will be able to download the digital instructions immediately when you are logged in and on your personal account page (click on My Account). Any PDFs will show up under My PDF Manuals. You will be allowed three downloads, so please save the file on your machine for backup.


If your diesel engine is getting a little tired, this kit can help keep it going for a while longer. You know that if you can just get it started it will go forever.. For you who are running waste vegetable oil, these plugs and relay setup will help start your engine in the morning if you did not fully purge the injection pump of grease the night before.

Remember: you will lose the automatic function on the 123 chassis and your glow light will not work properly You will have to think and count (seconds in your mind) when you start your engine. But I believe the benefits far outweigh the inconvenience of having the push the button on the dash. You will love how fast your diesel will start in the morning.

INSTALLATION NOTES: This kit can be installed with your average hand tools. There is one tool you may not have. You will be working with #8 gauge automotive wire (now that is thick wire!). You will need a crimping tool that can handle that size wire like the one shown below. Most standard crimping tools only handle terminals down to # 10 wire. We offer an inexpensive crimping just for this kit. Look below to order.

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