On my 85 300D I have a block heater that was installed by the previous owner. He told me it worked fine, but that he only used it a couple of times. He always stored his vehicle in an attached heated garage. Lately up here in Michigan we have had rather cold weather and when I went to use the block heater it seemed that it really didn't help. someone told me that if I had the block heater plugged in all night, that when I turned the ignition on my temp gauge should read at least 60. Also I was told that when I first plug the block heater in, I should hear a kinda' hissing sound like a coffee pot kinda' makes. Either way I don't have either symptom. Is there a way that I could test to make sure the block heater is in fact workin'?

Thanks, fellas.

(still cryin' in my beer about my '84 500SEL)
FrankieZ

[Edited by fz500sel on 12-30-2000 at 11:46 AM]

Hello fellow Michigander!

Plug the heater in. Let the engine cool down, like overnight.

Take off one glove long enough to place your hand on the block near the heater. If it's working you should have a warm, and oily, hand . If the heater isn't working, you will probably have a cold, oily hand

It's really cold here, but the oil should keep your hand from freezing to the block if the heater isn't working. :D

BCingU, Jim

A more definitive test is to measure the "current draw". Since a regular-duty engine block heater is typically rated around 550 watts, you should read between 4-5 amps. Between 3-4 amps you have either excessive resistance or a lighter-duty heater. If you read less than 3 amps your heater isn't doing much and should be replaced.

Barrie

Thanks, Barrie. Where should I check for this current draw at?

Another way to feel the heat without the oil mess, is to place your hand on the radiator. Since the blockheater is plugged into the waterjackets in the block, the water will heat up and start circulating on it's own. Depending on how cold it is, plugging my heater in usually gets the temp. a little above 40C.

Current draw can be measured with a multi-meter anywhere in series with the load (in this case, the heater). You can make a simple cable that's useful for measuring the draw of any AC appliance from an old extension cord . Cut one of the cord conductors and install a pair of insulated end connectors that will plug into your meter. The standard male bullet connector fits most meters. A word of caution: label the cord and keep it in your toolbox so that someone doesn't try to use it as a normal extension cord.

For more safety, I installed a current transformer in place of the bullet connectors. Either way, you have a handy little device with which you can run around the house measuring the power draw of all your appliances, as well as for basic troubleshooting.

Barrie

Re. comments on block temperature.
A block heater will not raise the coolant temperature to any particular (absolute) level. Your coolant temperature will be a function of the ambient temperature.

Think of putting a small space heater in an uninsulated garage on a cold winter day. Garage (internal) air temperature will rise and eventually stabilize at an equilibrium between the external temperature and the heater source. The lower the external temperature, the lower will be the internal temperature.

In short - think in terms of RELATIVE temperature INCREASE above ambient. For a given engine block, this will be a function of the heat-rise capability of the heater (i.e. heater power in watts).

Barrie

Happy new year to all. I was attempting humor, and agree it's better to feel around radiator, hoses, etc. Diesels aren't really oily, are they? ;)

Barrie, good point that measuring current draw will be definitive. I'd suggest that using current transformers is safer, at least to your multimeter. If you pick the wrong meter scale or unit setting... :eek:

Here is an interesting tool for measuring voltage and current which does not require you to break the circuit.

http://www.amprobe.com/amp_catalog_kwikie.html

We have one at work, and it is a good tool for approximations. It won't give laboratory-accuracy but it will quickly tell you if circuit is hot and drawing current.

BCingU, Jim

Easiest way to see if they are working is to use an ohmmeter. An open circuit could be due to a burnt-out element or the connector plug and wire are defective or not connected.

Somebody should build and market a male socket house current head that has an LED that comes on when the circuit is complete. This would take care of the guessing.

No hissing sound, but a soft "snap" instead
 

When I plug mine in, I can hear a soft electrical "snapping" sound when the contact is made. It's a quiet enough sound that I only hear it if there is no traffic on our street. It is about 400 watts, so imagine the sound of plugging in a 400 watt light bulb while it's turned on. I agree it would be nice to see the actual voltage at the block heater's AC input, as well as the current draw. I know I have 122 volts AC at my breaker box, but after 100' of 16/3 wire, who knows? Especially with all the salt and grime on the plug.