You are a god walking among men.

The reason for my shameless buttsmooching is the next question: any any chance are you planning to build and sell a few of these?

I just picked up a generic 12v solenoid, with plans to convert my 300d over, but this is way more elegant than my underhood wiring skills (as seen on my CD, which I converted a couple of years ago).

Thx

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Here's another option that uses the GP Relay as a fuse and pass through for stock wiring to the engine. In this scenario I use a Ford relay and a switch in the dash.

380SL Diesel Conversion Project

Yours is a little more elegant

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

I actually bought a Ford relay and was going to make a setup like the guy that has all the youtube videos from the NW but didn't want to hack up my wiring harness or build another one right now so i went back to modifying the old relay again.

i like the encapsulation of the parts and the fact that you did the same and used the mfg wiring harness. Did you then mount the Ford relay under your "new" part?

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"NEW" 1984 300D TD needs some love

No it's actually located up next to the firewall on the passenger's side. It's out of the way and because it's mounted directly to the chassis, I get audio confirmation that the solenoid is engaging as well as the LED in my momentary switch.

Attached Thumbnails

 

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

that's funny they bent over backward to make these things quiet and one of the things i like about this now is i can hear the OE relay click because i hit it before i put the key in the ignition.

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"NEW" 1984 300D TD needs some love

Hadn't thought about building any... shoot then i would have to get myself a gray coat with a Mercedes emblem and start making youtube videos, not that there is anything wrong with that.

why are you planning on converting yours over? just reliability?

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"NEW" 1984 300D TD needs some love

Signs on the walls of the garage. Don't forget the signs.

I did the coupe because it had the old loop plugs with the $$$$$$ early style controller, which died as soon as I got the car.

As I seem to be having problems with all the used preglow relays I buy for the 300d -- one last winter would not activate at under -8 F, the one I replaced it with worked great rest of last winter, then started staying on this winter when it got that cold, and fried my glowplugs -- I would rather just go manual or semi-controllable and not spend the $190 on a new Bosch box or $100 on a Korean one.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I had thought about putting a light on the dash that would show when power was going to the glow plugs, had kind of thought about dropping that but it could save a battery and the glow plugs if they stick shut like yours did.

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"NEW" 1984 300D TD needs some love

That was the beauty of the old Gorilla Knob system. The GP's were only on while you pulled the knob out, and there were extra points for positive engine shut-off when you pushed it all the way back in !!
No electronic relays, vacuum games or parts....

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

Why add a light on the dash when there is one in the cluster?
I simply rewired the glow controller so the light is connected to the glow plugs. I had one wire coming out of the controller to a toggle switch to +12v for manual control. Added a chime warning that sounds with power to the plugs. Loved it. First thing opening the door was to flip the glow toggle switch, chime sounds and cluster glow light goes on. Put key in ign and flip glow toggle switch to off before starting engine. Glow plugs were heating up while I sit and put key in ignition with ding dong ding dong in the background. Loved it.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked