I was poking around the underneath of my 83 300D this morning and lo-n-behold found a very well hidden block heater plug! Well now, last winter, my first as a diesel owner, was not fun what with trying to rig up lamps for heat, crossing my fingers in the morning, and even worse, having to use my rice-burner! So needless to say, I'm happy with this find. Prior to 10 below, is there some simple method to see if this thing is pulling some current? Would a continuity test at the plug end give me some indication as to the state of the heater element itself? How much should this pull amps-wise? I'm really surprised finding this, I guess I was looking in all the wrong places last year. I had the car out front being sold since I wasn't up to another winter fight. Maybe I'll keep it for another year now.

Rmmagow,

As far as I know there is no thermostst on the block heater. Plug it in and see if you notice a spark when you make the connection. Try a couple of times since you are using AC current.

If you get a spark, it will work. If not, probably won't work. You then might check with an ommeter. Should be in neighborhood of 25 ohms if its OK. Should pull about 5 Amps or more.

These values are just an educated guess but should tell if the heater will or will not work.

P E H

Why not just plug it in for a few hours and see if the coolant warms up? Of course you'll have to do this cold...... maybe overnight and check it in the morning. I think the heater is an all or nothing type deal so it will either work fine or not at all.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

that whenever I plug in my block heater I would hear a slight hiss and sometimes a light gurgling sound as if some coolant is moving around. I would not hear these noises normally until I plug the block heater in.

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Frank
84 500SEL EURO 101K ( JUST LIKE MY 1ST WIFE. GLAD TO GET RID OF HER! )
85 300D 310K (sold)
90 350SDL 184K sold
83 300D 118K (sold)
88 300E 153k (sold)
93 400E 105K (sold)

generally i used mine if the temp overnight was going below +15
deg F. if it's not going to below 0 def F then if you have time you can plug in a couple of hours before startup. there is a remarkable difference in the warmup time when using a block heater.
you will notice it immediately.
let's not hope for winter yet though..:p

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

Last winter on my 83 when I was running the block heater I noticed a little drip of coolant, yet it won't leak just driving around. What is the deal with this? I also only use mine when below 20*F. Anyone have a heavy duty timmer? I'm thinking of getting something like that this year. Another nice thing for the motor in the winter is a semi or full synthetic oil, the difference is unbelievable in speed of turning over. Btw, I just stopped in to wally world today and picked up some Mobil 1 15w50 supersyn, 5qt jug for $18.88, it has a pour point of -49*F.

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k