The glow plug relay in my 85 300D has been intermittent ever since I acquired it. It would sometimes not supply power to the glow plugs when I turn the key to on, no click, no glow plug light, nothing. I finally took it apart a month ago and found a lot of solder flux bleeding through the conformal coating (humidity coating). I didn't have any solvent to remove the coating before resoldering it which made a mess . After I was done, the relay stayed on constantly including the glow light and would not shut off unless the the key is off. Instead of spending more time trying to fix it I decided to make it manual control. I removed the violet and the red/blk wires from the small 4 pin connector on the glow relay, solder a long wire to the red/blk wire contact and brought it in the cabin and stuck it into the cigarette lighter to glow the glow plugs till I decide where to add a push button switch.
After a month of that I got tired if it but I didn't want to drill any holes anywhere for the switch, I decided to use a reed switch and a magnet for the manual glow control.

The reed switch is under the wood in the center console by the gear selector. The red ribbon is tied to a ring magnet. I wired in a buzzer which sounds in addition to the glow light in the cluster whenever it's glowing. I wanted to be able to glow without the key so tapped into the hazard switch's red/white wire which is hot at all times.

Shot a video. How do you like it?
CLICK TO PLAY

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The red ribbon kind of clashes with the Zebrano - other than that I like it

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Current Stable

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

Fortunately, ribbon color can be easily changed.

This mod can be easily reversed back to stock by putting the 2 wires back into the connector housing and installing a good glow relay.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

That's neat!

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

You have also created a security system to make it difficult for anyone else to start your car (depending on ambient temperature, compression, coolant temp, etc.). Nicely done!

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Hopefully that feature will never get used. I am loving this manual glow. When engine is warn I just turn the key- no glow enabling magnet needed. Looks like I picked a good spot for the reed switch. I tied the magnet ribbon to the gear selector so that when I take it out of park, it pulls the magnet away and ends the glow! Think I will change to a black ribbon that stands out less.

CLICK TO PLAY!

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

NIce!

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'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter

Much to do about nothing. An used GP relay can be had for $10-20. Your sweat labor and parts is worth more than that. It doesn't add VALUE to anything. But if you want to tinker then ...

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

A fun tweak.

Something interesting to consider if you're interested in "manualizing" your car. It's my plan, for my '79. Especially since GP relays are NOT that cheap for the older cars, mainly because it's hard to find them used these days and new they are big money.

However, for the '85, I'll hang on to the auto feature. I just pick up spare relays any time I see them at the junkyard.

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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

You are missing the most important benefit of manual glow system, which is to lower their usage and thus increase their life expectancy. Considering what a PITA glow plugs are to replace, it is a very worthwhile mod. Ever since going to manual glow on my diesels, I have not had to change a glow plug yet. I can easily revert back to a stock system when it's time to sell by changing out the glow relay and putting one wire back into the 4 pin connector.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

^X2

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Current Stable

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

Love the manual glow on my conversion. Mine is much less cool, just a toggle switch with a bright orange GLOW PLUG label over it. Some artists work with musical instruments, some with canvas and paint, some with pencil, some with MBZ diesels.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Glow plugs in a 617 are hard to replace? Maybe if you have big hands. I can do all five in half an hour with just combo wrenches.

I also noticed in the video that the seat belt buzzer is still active. I unplugged mine about eight years ago and haven't missed it since.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

I cannot see how it can increase the life span of the GP. What happens if you leave it on by mistake? I am sure the relay will cut off the GP faster than you turining it off when the engine fires. You have not changed any GP does not mean you would have changed some if you had stayed with the GP relay. It is all wishful thinking. If you like it and give you peace of mind then so be it. I just do not want to explain to someone who drives it for the first time. I do not normally let anyone drive my car but there is always exception.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

That is not a seat belt buzzer. It's one I added as notification that the glow plugs are on since I can glow w/o the key.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked