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#2797959 - 11/09/12 06:05 PM How do you test a block heater with a multimeter?
Carnoobie Offline


Registered: 06/21/11
Posts: 661
Loc: Canada
Theres a thing called Plug alive that is easier but its $20 and for a one time thing i really didnt want to waste $20 if I can do this test with my multimeter. Do I connect the prongs from the MM to the plug end of the Block heater? Even though my plug is 3 prongs.

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#2797972 - 11/09/12 06:22 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
RiceCake Offline


Registered: 09/22/12
Posts: 1044
Loc: Coldtown, Canada
Connect the multimeter to both prongs of the AC cord with it set for Ohms, resistance measuring.

It should measure something between 25 and 8 ohms which equates to between 500 and 1500 watts. If its less then 8, its probably a dead short and will blow a fuse. If its more then 25 your block heater is less then 500 watts, so, I'd be curious if its still working, most block heaters are at least 500 watts.

If you get an open circuit, you've got an issue.

The rounded third prong of all electrical cords are ground, they're there to divert power to keep it from electrocuting people and otherwise generally serve no active role in powering anything. The two blades are what you should measure from.


Edited by RiceCake (11/09/12 06:24 PM)

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#2797973 - 11/09/12 06:24 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
Dave Sherman Offline


Registered: 01/03/06
Posts: 978
Loc: Ohio
Set it to measure resistance, and measure between the two flat blades. I'm guessing a block heater is between 100-500 watts, so you should be getting a resistance of between 30-150 ohms. If it reads overflow or extremely high, then you've got a problem.
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#2797975 - 11/09/12 06:26 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
Dave Sherman Offline


Registered: 01/03/06
Posts: 978
Loc: Ohio
My mistake RiceCake, I thought the block heater on our old GMC 6.2 diesel was only 300 watts, so I was guessing on the wattage.
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#2797976 - 11/09/12 06:26 PM Re: How do you test a block heater with a multimeter? [Re: RiceCake]
Carnoobie Offline


Registered: 06/21/11
Posts: 661
Loc: Canada
Originally Posted By: RiceCake
Connect the multimeter to both prongs of the AC cord with it set for Ohms, resistance measuring.

It should measure something between 25 and 8 ohms which equates to between 500 and 1500 watts. If its less then 8, its probably a dead short and will blow a fuse. If its more then 25 your block heater is less then 500 watts, so, I'd be curious if its still working, most block heaters are at least 500 watts.

If you get an open circuit, you've got an issue.

The rounded third prong of all electrical cords are ground, they're there to divert power to keep it from electrocuting people and otherwise generally serve no active role in powering anything. The two blades are what you should measure from.


Thanks.

When i touch the MM prongs to the prongs on the cord plug, should i have them just touching parellel to the cord prongs (like touch them side to side) or just the tip of MM prongs?

Does it matter if i do it with the car hot or cold? Gonna do it tonight.

Is this test a sure test like with the plug alive $20 tool?

And finally, so 25 or just under is technically the # im wanting?


Edited by Carnoobie (11/09/12 06:30 PM)

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#2797980 - 11/09/12 06:28 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
Dave Sherman Offline


Registered: 01/03/06
Posts: 978
Loc: Ohio
Originally Posted By: Carnoobie
Originally Posted By: RiceCake
Connect the multimeter to both prongs of the AC cord with it set for Ohms, resistance measuring.

It should measure something between 25 and 8 ohms which equates to between 500 and 1500 watts. If its less then 8, its probably a dead short and will blow a fuse. If its more then 25 your block heater is less then 500 watts, so, I'd be curious if its still working, most block heaters are at least 500 watts.

If you get an open circuit, you've got an issue.

The rounded third prong of all electrical cords are ground, they're there to divert power to keep it from electrocuting people and otherwise generally serve no active role in powering anything. The two blades are what you should measure from.


Thanks.

Does it matter which black or white prongs from the MM goes to which prongs on the cord plug?

Does it matter if i do it with the car hot or cold? Gonna do it tonight.

Is this test a sure test like with the plug alive $20 tool?


No, when measuring resistance it does not matter which lead goes to which blade.
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#2797983 - 11/09/12 06:33 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
RiceCake Offline


Registered: 09/22/12
Posts: 1044
Loc: Coldtown, Canada
^

You're measuring a big giant resistor, polarity is irrelevant.

And no, doesn't matter hot or cold. The block heater is like a giant toaster that's always on, it doesn't specifically do anything when hot or cold.

And yeah basically. If you get resistance anywhere from 8 to about 50 you're fine. Make sure the prongs for the block heater aren't covered in crud, that will show an increased resistance.


Edited by RiceCake (11/09/12 06:34 PM)

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#2797984 - 11/09/12 06:33 PM Re: How do you test a block heater with a multimeter? [Re: Dave Sherman]
Carnoobie Offline


Registered: 06/21/11
Posts: 661
Loc: Canada
Originally Posted By: Dave Sherman
Originally Posted By: Carnoobie
Originally Posted By: RiceCake
Connect the multimeter to both prongs of the AC cord with it set for Ohms, resistance measuring.

It should measure something between 25 and 8 ohms which equates to between 500 and 1500 watts. If its less then 8, its probably a dead short and will blow a fuse. If its more then 25 your block heater is less then 500 watts, so, I'd be curious if its still working, most block heaters are at least 500 watts.

If you get an open circuit, you've got an issue.

The rounded third prong of all electrical cords are ground, they're there to divert power to keep it from electrocuting people and otherwise generally serve no active role in powering anything. The two blades are what you should measure from.


Thanks.

Does it matter which black or white prongs from the MM goes to which prongs on the cord plug?

Does it matter if i do it with the car hot or cold? Gonna do it tonight.

Is this test a sure test like with the plug alive $20 tool?


No, when measuring resistance it does not matter which lead goes to which blade.


On my MM i dont have a 0 resistance setting. I have 20K, 200K, 2000K, 200, 2000 and 20M. What the [censored]?

Before i test it, should i not figure out how many Watts my block heater is? I dont even know how to find out cause i dont know the specs or brand.


Edited by Carnoobie (11/09/12 06:35 PM)

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#2797987 - 11/09/12 06:35 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
RiceCake Offline


Registered: 09/22/12
Posts: 1044
Loc: Coldtown, Canada
Set it to 200. Its because most resistances you'll measure on electronics are in kilo-ohms (Ie: 200K).

The "200" setting will measure up to 200 ohms (0-200 ohms).

And, no, don't worry about it. You can calculate the wattage after if you want but its not that important. Block heaters either fail or work, so it won't be "out of spec".

Its a giant toaster, if its bad, it'll just show infinite resistance (open circuit).


Edited by RiceCake (11/09/12 06:36 PM)

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#2797988 - 11/09/12 06:35 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
bullwinkle Online   confused


Registered: 10/09/04
Posts: 6777
Loc: Cincinnati, OH, USA
Set it on 2000, let us know the number. I would bet the cord is the problem if the resistance is too high.
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#2797991 - 11/09/12 06:41 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
Carnoobie Offline


Registered: 06/21/11
Posts: 661
Loc: Canada
ok gonna test it right now on 200 setting and again on 2000 setting.

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#2798001 - 11/09/12 06:51 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
Carnoobie Offline


Registered: 06/21/11
Posts: 661
Loc: Canada
No reading.

I turned my MM to 200 setting then 2000 and it just showed "1" and touched hte prongs to inner sides of the plugs prongs (even tried through the holes of the plug prongs) and nothing.

I had to change out this plug few weeks ago cause i accidentally busted my old one and this has been a major nousense ever since.


Edited by Carnoobie (11/09/12 06:52 PM)

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#2798016 - 11/09/12 07:07 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
Carnoobie Offline


Registered: 06/21/11
Posts: 661
Loc: Canada
ok i just notice one thing, the ext cord that ive been plugging into is dead! So I switched out another ext cord, plugged in my hair dryer to that to make sure it works and it does. And plugged in my car to the new cord. Gonna see if this works now.

But either my MM is acting finicky or the resistance is messed up cause it wouldnt even measure.

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#2798024 - 11/09/12 07:14 PM Re: How do you test a block heater with a multimeter? [Re: Carnoobie]
bmwtechguy Offline


Registered: 06/15/04
Posts: 2584
Loc: South Carolina
Hey, set meter to 200 ohms resistance and touch the two leads together on your meter to see if it is working. When touched together, it should show something less than 1 ohm....maybe like .2 or .4 or less. It it shows infinity or OL for over limit (open circuit), then you may have a meter problem or one of the leads is bad. Hopefully just your extension cord was the real culprit.

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#2798029 - 11/09/12 07:17 PM Re: How do you test a block heater with a multimeter? [Re: bmwtechguy]
Carnoobie Offline


Registered: 06/21/11
Posts: 661
Loc: Canada
Originally Posted By: bmwtechguy
Hey, set meter to 200 ohms resistance and touch the two leads together on your meter to see if it is working. When touched together, it should show something less than 1 ohm....maybe like .2 or .4 or less. It it shows infinity or OL for over limit (open circuit), then you may have a meter problem or one of the leads is bad. Hopefully just your extension cord was the real culprit.


I did that, got 0.2/0.3 when i touch the two prongs of the MM together.

This is the plug i put on my block heater cord, is it not the right specs? Can you guys check it out and tell me if it is?

http://www.homedepot.ca/product/3-wire-cap-plug-ebony/903844

I tell you, if i can find out that the heater is working, im gonna switch out this plug cause its the biggest POS ever. Its super tight to get in and out, ive never dealt with a ridiculously tight plug to put in a socket before. I made sure all the prongs are straight and line up with the ext cord socket and it does but cant figure out why its so tight, [censored]?



Edited by Carnoobie (11/09/12 07:22 PM)

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