radiator fan relays 1 and 3 keep blowing

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Dusty rug, Apr 20, 2020.

  1. Dusty rug

    Dusty rug Member

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    i have anti freeze boiling out of its reservoir (engine coolent) with the over heating temp signal going off, only when i drive more then 30 miles on one go. ive changed the temp sensor above the engine and changed the thermostat and it still does the same thing. when i changed the relays the problem when away and i drove 100 miles on one go (went to Wyoming from Denver) on my way back so 150 miles the problem came back and i pulled the relays and both of those were blown. i looked at the wiring but i know next to nothing about how to fix this issie, but im pretty sure it might be a short to ground, i jsut dont even know where to begin to find it.

    does anyone know how i should go about fixing this issue?
     
  2. rjparker

    rjparker Tu Humilde Sirviente

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    Its pretty simple from a circuit standpoint. What is odd is its blowing relays. Usually you blow fuses. So you have to be reasonably good with a multimeter and first determine if the coil or the contacts on the relays are burning out. The contacts are the switching power part of the relay and the coil is part of the control. Next one might measure the current being drawn with a dc amp clamp (a more specialized meter).

    I would speculate that one of the fans is drawing excessive power but not enough to blow the 30 amp fuses that feed each relay. Or the 30 amp fuses have been replaced with significantly higher rated fuses by mistake. In any case, excessive current can burn out relays but from the sounds of it your problem would have to draw less than 30 amps but much higher than normal for the fan. My guess would be one of the fans is partially or intermittently shorted.

    By the way relay 2 will cause the fans to run at reduced speed and current so there is an outside chance a failure with it may cause an over current when it changes position.

    Bottom line: This is a simple enough circuit that any halfway decent mechanic should be able to diagnose it quickly. Given you are risking your engine I would get someone to find the problem.

    cooling fans.jpg
     
  3. ChapmanF

    ChapmanF Senior Member

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    It would be great to know what you mean by the relays being "blown". Are the coils burned out? Or has something happened to the contacts, or they failed mechanically.

    Something happening to the coils would be downright weird. Excessive fan draw wouldn't explain it.
     
  4. rjparker

    rjparker Tu Humilde Sirviente

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    A possibility is one of fans has a bad bearing and when #2 and #3 relay energize there is not enough voltage to start the fan. An electric motor that is stalled will draw a large current. If the fuses are oversized its possible the relay contacts may burn.

    Another scenario is an intermittent frequently cycling coil which forces the contacts to see starting surge currents almost continously combined with excessive arcing of the contacts. The first scenario would probably point to fan #1 where the second scenario might be a result of an intermittent break in the common battery power to this circuit.

    The third and most likely scenario is bad assumptions or an inaccurate description of the problem. For example it may be assumed the relays are bad because installing new ones "fixed" it. But it could be a wiring fault that was jiggled in the process. An inaccurate description could be the fuses are blowing rather than the relays.
     
    #4 rjparker, Apr 22, 2020
    Last edited: Apr 22, 2020
  5. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Relays and fuses are side-by-side in the underhood box. Perhaps a component identification error is included in the OP's presentation of the problem?
     
  6. rjparker

    rjparker Tu Humilde Sirviente

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    I think we have a failure to communicate.
     
    #6 rjparker, Apr 22, 2020
    Last edited: Apr 22, 2020
  7. Dusty rug

    Dusty rug Member

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    sorry for being late with replying life an all, i wasnt aware there are fuses that power the radiator fans, does anyone know where those are located on the car?

    about my problem it all started when i was coming back from an 3000 mile road trip, everything was fine then out of no where when i was pushing it harder then i should have i got an check engine code for the temp senor then not long after that my coolant boiling out start. i only think the relays went bad since i tried hooking them to an 12 volt battery and didn't hear any clicking.

    both my fans work when i got the ac on, i did notice that they dont turn on when i put my prius into maintenance mode but thats with the same relays that i think might be bad.

    the ball bearing for the fan sounds like its plausible, what kinda tests can i preform to narrow down the Couse of my issue, i have an multimeter that i just got from amazon a
    KAIWEETS Digital Multimeter TRMS 6000
    , i am trying to learn how to use it since ive never dealt with this kinda issue, any tips would be very grateful.
     
    #7 Dusty rug, Apr 22, 2020
    Last edited: Apr 22, 2020
  8. rjparker

    rjparker Tu Humilde Sirviente

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    The fuses are in back right of the engine compartment. But if the fans both run with the AC then the fuses and the relays are 99% sure to be ok. Plus the fans are not even necessary at speed since enough air flows through the radiator.

    Idle, slow speed and stopped is when fans become energized. You probably have a cooling system problem like a water pump, thermostat or even a head gasket. If you value your vehicle take it somewhere and have it diagnosed.

    By the way, if you pulled out the first relays and tried to operate them using a 12v battery you could easily smoke the normally closed contacts through a wrong connection. Again, if the fans run in AC mode, the fuses and relays are ok.
     
    #8 rjparker, Apr 22, 2020
    Last edited: Apr 22, 2020
  9. Dusty rug

    Dusty rug Member

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    its true when i hook up my obd2 scan tool, the temps stay around the 200F mark but anytime i try to go up hill the temps shoot up to 300F and the temp sign turns on and i slow down so it cools back down and the light turns off. i was thinking it was an coolent system issue too, ive replaced the thermostat an im not sure how to test the water pump to see if its at fault. but with the head gasket, wouldnt there be more symptoms then over heating under heavy loads? i thought my main issue was that the fast speed for the fan wasnt kicking on, an head gasket is alot more scary to me then most other things
     
  10. rjparker

    rjparker Tu Humilde Sirviente

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    With a good scan tool you can turn on and off the fans and verify when they are running. Same should be possible on the water pump. Realize it has two water pumps, one fo the engine and another for the inverter. There are coolant water tests for head gasket problems. Sometimes you will get white smoke (water vapor) out of the tailpipe when you have a bad head gasket. It would also use water to the point where their was not enough.
     
  11. Dusty rug

    Dusty rug Member

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    thanks for the advise im going to get an combustion leak test kit tomorrow and see if its the head gasket, fingers crossed its not.
    i got an medium grade scan tool that can data steam, but i would be interested in knowing what tool can turn off and on the parts in the prius. i was thinking it over and i did explain the problem wrongly, my coolent isnt boiling infact everytime i take a peak when the temp is high its not boiling at all, it is hot tho. whats really happening is its spraying out of the reservoir from the pressure relief valve under the cap, see the pic i took this moring after i got home from work, about an 10 mile drive. thanks for your quick response, hopefully i can get this fixed so i can enjoy my prius, i love this car so much

    the white residue is coolent that was sprayed out
     

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  12. rjparker

    rjparker Tu Humilde Sirviente

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    Techstream is the scanner from Toyota but its expensive. The “car scanner” app can see most of the data and works with a bluetooth obd2 reader. Some data:
    B6D4CBCA-BB3C-4029-8173-DE7C29D8BD32.jpeg
     
    #12 rjparker, Apr 23, 2020
    Last edited: Apr 23, 2020
  13. rjparker

    rjparker Tu Humilde Sirviente

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    Take a picture of the area of the fuse box were you replaced the relays and try to identify the relays changed. There are three involved. It is possible both fans would run in low but not high in some failure modes. Relay 1 and 2 of the above diagram have to work to go to high. The green wire LG enables high while the blue wire L is low.
     
  14. Ronald Doles

    Ronald Doles Active Member

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    "Whats really happening is its spraying out of the reservoir from the pressure relief valve under the cap"

    You may have a blown head gasket that is leaking cylinder combustion pressure into the cooling system. That combustion pressure would exceed the 15 psi rating of the radiator pressure cap and be vented through the cap and possibly into the overflow container. You might check the coolant level in the radiator overflow container.
     
  15. Dusty rug

    Dusty rug Member

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    alright ive highlighted the relays that i replaced and what seemed to make my coolent issue go away for an long drive, just for it to rear its head back when i was going up a pretty steep hill on the highway, i determined that it was an bad relay from the process of elimination. mind you it only sprays out coolent when i have to keep the throttle in power for expended periods. i dont have any issues when driving on level ground. ive read on other fourms that it might be an blockage in the system too or like what you guys have said an failing water pump or head gasket.
     

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  16. rjparker

    rjparker Tu Humilde Sirviente

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    I guess we should take your findings at face value that somehow your relays failed (maybe by putting a 12v battery directly across the contacts) and replacing two seemingly “fixed” it. The thing is there are three relays used to run two fans. As it turns out, number one fan relay could be burned and you could still have low speed on both fans. When it tried to go high, one fan could then stop. A long shot but you probably need to check (or maybe just replace) the fan relay you did not change. See pics of fuse box and of the current flow highlighted in yellow for low and high fan speeds.

    You can test relays with your meter on ohms only, no power applied by checking for continuity across the coil as one step and continuity across the normally closed contacts. Then you could power it with 12v on the coil only, listen for the click and check for continuity across the normally open with the coil energized. If this does not make sense then find somebody who does. Or just shotgun it (eg change parts and fuses).
     

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  17. Dusty rug

    Dusty rug Member

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    good news i replaced all of the fuses and it does seem to be working better now, tho i am kinda worried when i was on the highway going 70 mpr i would see my temps go from 190 to 230 like straight shoot up in temps then back down, it would linger on the high side then the lower. do you think a weak or failing water pump could be the root of all my problems with this? what can i do besides take it to a shop to get tested?

    this virus really has me working very long hours so i haven't been able to check up often
     
  18. rjparker

    rjparker Tu Humilde Sirviente

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    Can't say that I have ever watched the behavior of the temperature at high speeds but I would expect it to hold steady. First, fans have nothing to do with air flow through the radiator at 70 mph. There is plenty of air flow already. Fans are for slow speed and idle conditions.

    What happened on the combustion leak (head gasket) test? This is important.

    I might wonder about that thermostat you changed. Perhaps its sticking closed too long? Maybe 230F occasionally is ok. I suppose it could be an intermittent water pump but that would likely make it overheat at any speed or even idle at times. So I would think that is not the issue.
     
  19. Dusty rug

    Dusty rug Member

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    the combustion leak tested negative for any CO2 in the coolant lines, i would have thought this was an non issue too but itll still over heat and spray coolent all over my engine even at outside temps of 10F.

    AISIN THT-017 Thermostat with Housing is what i used off amazon, maybe i should have looked for an OEM part thats higher quality if thats the case here. after doing an long drive this morning i was starting to think if there was enough coolent flow so prevent this from happaning
     
  20. rjparker

    rjparker Tu Humilde Sirviente

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    Have you changed the radiator cap?
     
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