1. Offline

    briantompo New Member

    Member Since:
    Sep 28, 2006
    Posts:
    10
    Likes Received:
    0
    Location:
    Florida
    Your Vehicle Year:
    2005 Prius
    Hello,
    My Toyota engine block heater just started tripping the garage GFI outlet where it worked previously. I've tried different outlets on different circuits as well as different extension cords...all with the same result. The block heater has been flawless in the Prius for about 5 years, and tests OK as far as I can tell. Resistance at 70F is 35 Ohms, open between both prongs and ground, and the ground prong has zero resistance to the chassis. Plug is still like new and nothing changes if I move the plug around or bend the cord. I can't find a short anywhere and the prongs are clean and free of corrosion. A 500W halogen lamp and a circular saw both work in the same outlets, same extension cords without tripping the GFI.

    Can anyone offer any additional troubleshooting suggestions or similar experience with their block heater? I'm out of ideas.

    Thank you, Brian
  2. Online

    bisco cookie crumbler

    Member Since:
    May 11, 2005
    Posts:
    17,371
    Likes Received:
    2,732
    Location:
    boston
    Your Vehicle Year:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    try a hairdryer? maybe there is some moisture somewhere.
  3. Offline

    Dark_matter_doesn't Prius Tinkerer

    Member Since:
    Aug 8, 2009
    Posts:
    641
    Likes Received:
    123
    Location:
    Seattle, WA
    Your Vehicle Year:
    2010 Prius
    Model:
    IV
    Does the GFI pop immediately or after the heater gets hot?
  4. Offline

    frodoz737 The Mechanic

    Member Since:
    Aug 26, 2010
    Posts:
    1,479
    Likes Received:
    360
    Location:
    TX
    Your Vehicle Year:
    2010 Prius
    Model:
    II
    Your heater element or cord is shorting or burned out. Check the plug, cord and terminals first for wear, security and corrosion. Contact cleaner is your friend. Removing the element/cord assy will make inspection easier if no obvious damage is found. Wiring can be repaired. Ring the wiring and element seperatly. If all looks good, go to dealer parts counter and ask to ring out a new one off the shelf to verify. If they do not have one, ask someone in service if they will print out the resistance checks for you off the manual. Please and thank you sometimes still works. If not, someone here might give you their resistance readings for a comparison.
  5. Offline

    briantompo New Member

    Member Since:
    Sep 28, 2006
    Posts:
    10
    Likes Received:
    0
    Location:
    Florida
    Your Vehicle Year:
    2005 Prius
    Thanks, so far for the suggestions. D Matter- the GFI pops right away.
    Would someone with a Toyota block heater measure the resistance across theirs and report back? I measured 35 Ohms on mine. The math seems correct for 400ish Watts.
    Thanks, Brian
  6. Offline

    Chuck41 New Member

    Member Since:
    May 21, 2008
    Posts:
    38
    Likes Received:
    0
    Location:
    Midwest
    Your Vehicle Year:
    2008 Prius
    Hi
    I measured the resistance of my EBH and it was ~ 35 ohms.
  7. Offline

    frodoz737 The Mechanic

    Member Since:
    Aug 26, 2010
    Posts:
    1,479
    Likes Received:
    360
    Location:
    TX
    Your Vehicle Year:
    2010 Prius
    Model:
    II
    "I've tried different outlets on different circuits as well as different extension cords...all with the same result."



    Your drawing more amps than your GFI limits while plugged in. My recommendations stand. It is a dedicated system. Worst case it's only $59 and a little time to fix. Best wishes.
  8. Offline

    jpadc Type before I think too often

    Member Since:
    Sep 9, 2008
    Posts:
    334
    Likes Received:
    27
    Location:
    Indianapolis and Northern Wisconsin
    Your Vehicle Year:
    2008 Prius
    Model:
    N/A
    Brian:

    While you had the ohm meter out did you check the resistance in the cord? Likely you will find that it is bad / shorted. A few of us have found the problem at the 3 prong end due to wear of plugging and unplugging it in an extension cord. With that, of course, you can just cut plug off and replace it. For most of us, unfortunately, the problem is at the connector to the heating element and for that, you just have to replace the entire thing.

    Bob
  9. Offline
    • Moderator

    efusco Troll Slayer

    Member Since:
    Nov 26, 2003
    Posts:
    19,842
    Likes Received:
    1,062
    Location:
    Nixa, MO
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    I third the suggestion that it's the cord...they're known to wear out, usually just back of the reinforced area behind the plug. You can cut that off and splice on a new plug or replace the whole EBH and cord set (you can't just replace the cord, usually, b/c getting it off of the EBH is impossible as the whole thing just crumbles.

    I've done both, the spliced fix worked fine if you do a good job. I would, however, suggest you use a small extension on the end of whatever cord you decide to go with. they make some that are about 8" long--let that take the wear/use and wear out, then all you ahve to do is replace the 8" extension instead of fiddling with the main cord.
  10. Offline

    ursle Gas miser

    Member Since:
    Jun 28, 2006
    Posts:
    902
    Likes Received:
    167
    Location:
    NH
    Your Vehicle Year:
    2011 Prius
    Model:
    Four
    I'd pull the heater out of the car and check the chord, if it isn't the three prong plug shorting it could be that the wire was rubbing somewhere and shorted, lots of motion where electricity is concerned, lots of motion where cars are concerned.
  11. Offline

    kornkob New Member

    Member Since:
    Dec 20, 2011
    Posts:
    128
    Likes Received:
    12
    Location:
    Wisconsin
    Your Vehicle Year:
    2009 Prius
    Model:
    ----USA ONLY----
    It is my understanding that GFIs can get more touchy as they age and as they see more use. You might consider changing the GFI itself.
  12. Offline

    briantompo New Member

    Member Since:
    Sep 28, 2006
    Posts:
    10
    Likes Received:
    0
    Location:
    Florida
    Your Vehicle Year:
    2005 Prius
    Thanks, everyone for the suggestions. I'll update when I find the problem and repair or replace. I was hoping to avoid removing the heater to troubleshoot but I've exhausted the easy approach. I'm confident the fault is in the heater and NOT the house and unfortunately, it's not the plug or strain relief. Thanks again, Brian
  13. Offline

    Mendel Leisk Senior Member

    Member Since:
    Oct 17, 2010
    Posts:
    3,720
    Likes Received:
    620
    Location:
    Greater Vancouver, BC, Canada
    Your Vehicle Year:
    2010 Prius
    Model:
    N/A
    If resistance across block heater prongs is (normal) 35 ohms: maybe a problem with your extension cord.
  14. Online

    bisco cookie crumbler

    Member Since:
    May 11, 2005
    Posts:
    17,371
    Likes Received:
    2,732
    Location:
    boston
    Your Vehicle Year:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    i have replaced a few for this reason.
  15. Offline

    ngc4565 Member

    Member Since:
    Nov 28, 2011
    Posts:
    155
    Likes Received:
    16
    Location:
    Pennsylvania
    Your Vehicle Year:
    2010 Prius
    Model:
    IV
    In that case you have a short between the neutral and ground wires. The purpose of a GFI is to detect this very situation. Try replacing the plug first.
  16. Offline

    fuzzy1 Senior Member

    Member Since:
    Feb 26, 2009
    Posts:
    6,529
    Likes Received:
    1,581
    Location:
    Western Washington
    Your Vehicle Year:
    2012 Prius
    Model:
    Three
    No, he has an open between neutral (i.e. one of the prongs) and ground.

    I do hope he used a digital meter, or adjusted the range of his analog meter, to verify that 'open' exceeded something like 100kohms. On an analog meter without a range change, leakage strong enough to trip the GFCI could still register as 'open'.
  17. Offline

    Patrick Wong DIY Enthusiast

    Member Since:
    Mar 8, 2008
    Posts:
    12,357
    Likes Received:
    2,930
    Location:
    Green Valley, AZ
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A
    Since the OP tested the GFI and extension cord with other devices that require substantial power, my guess is that the power cord to the block heater has an intermittent problem which did not manifest itself during the ohmmeter testing.
  18. Offline

    ngc4565 Member

    Member Since:
    Nov 28, 2011
    Posts:
    155
    Likes Received:
    16
    Location:
    Pennsylvania
    Your Vehicle Year:
    2010 Prius
    Model:
    IV
    No, I beg to differ. The neutral and safety ground should be isolated (i.e. open) at the load. The entire purpose of a GFI is to detect an imbalance of current between the hot and neutral wires. The fact that he sees the same resistance between the hot terminal and the neutral and ground proves that there is a short.
  19. Offline

    fuzzy1 Senior Member

    Member Since:
    Feb 26, 2009
    Posts:
    6,529
    Likes Received:
    1,581
    Location:
    Western Washington
    Your Vehicle Year:
    2012 Prius
    Model:
    Three
    Are we reading the same OP?

    I read it as:
    35 ohms hot to neutral (prongs);
    Open hot (prong) to ground;
    Open neutral (other prong) to ground;
    Short ground to chassis.
  20. Offline

    ngc4565 Member

    Member Since:
    Nov 28, 2011
    Posts:
    155
    Likes Received:
    16
    Location:
    Pennsylvania
    Your Vehicle Year:
    2010 Prius
    Model:
    IV
    My apologies - I clearly misread the original post.

    Peace on Earth and happy holidays.

Share This Page