Add mine to the surge of cold weather starting threads!

On the '81 300D, my glow light isn't coming on and the car is extremely hard to start. I'm going through the list of usual procedures and I've found something that seems a little strange. My relay is shows 12.5v at the pins during the glow period, but after it clicks (approx 60 sec) I'm still reading 2.8v at the pins. Is this normal, or should the relay be cutting the voltage to 0?

Plug/wire 5 is reading infinite so I know I've got more testing to do (can't wait to pull the plugs, it's like 12F degrees out there right now), but I figure if this voltage at my relay is abnormal and the relay needs to be replaced anyway, I'd just order one of those kits with the duraterm plugs and the after-glow relay. In other news, Fastlane doesn't show that kit as being available for my car, anyone suggest another source?

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1981 300D - {172,000}
1971 220D {Sold to TomJ}

Give them a call and see if they can source the relay, I have a post-glow in my 300D and it does seem to make a difference after cold starts.

Didn't have time to call them today but I was hoping to verify that this is abnormal before I start buying parts. Anybody know if there should still be some voltage at the pins when the relay is off? Or perhaps point me in the direction of a schematic that might show the proper function? I've searched and can't seem to find anything.

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1981 300D - {172,000}
1971 220D {Sold to TomJ}

I've only checked for voltage at the strip fuse. Check resistance on all the pins to verify the relay/cables are good or bad. Chances are that you have a bad plug.

Dieselgiant has a good DIY on this subject.

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)

Yeah, I do have a bad plug and I intend to order a new set to replace the lot. I have followed DieselGiant's procedures to get to this conclusion . . . but my concern is that voltage at the pins on the relay after the click. I haven't been able to find anything that states whether or not the voltage to the plugs is supposed to be cut to 0, or if that 2.8 that I'm reading is indicative of a relay failure . . . in which case I'm ordering a relay as well as the plugs. Maybe I should just take it apart and looks for some corroded contacts that are hung up or something.

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1981 300D - {172,000}
1971 220D {Sold to TomJ}

I don't work much with DC, but here's an AC phenomenon. 'Ghost Voltage' is a reading that meters sometimes pick up from the magnetic waves of the current in nearby wiring. Sometimes is as high as 10 or 12 volts in 240v circuits. Inexpensive meters tend to pick it up a bit more than more expensive meters or those with shielded leads. It would seem to me that, given the nature of AC and DC, the problem would be much less likely to present itself on a DC circuit ---- but it is a consideration. Please keep us posted.

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

There should not be 2.8 volts at the glow plug relay pins (ones that go to the glow plugs) after the relay clicks off. Verify the measurement with another meter, prefereably an analog DC meter.

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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

Check the voltage at the glow plugs with the harness plugged in at the relay,i would be surprised if you still see the 2.8V.I dont know what sort of meter you are using but as John said its not out of the ordinary to see these sort of voltages on an open circuit,on my Fluke meter they are usally in the millivolt range. Don

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Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles

You mean my $15 Radio Shack special meter might be off?

I checked the voltage at the plug end of the wire, and indeed it is zero. Might be something to that interference idea . . . or my meter is only worth the $15 I paid for it.

Called Lee today, the after-glow kit has been backordered since December. Expected availability is late next week, so I guess I have a few days to decide if I want to upgrade or just replace the plugs.

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1981 300D - {172,000}
1971 220D {Sold to TomJ}