Heater not heating but no air lock?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Frijjj, Oct 22, 2019.

  1. Frijjj

    Frijjj Junior Member

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    So I've replaced the thermostat and the water pump. I've got rid of the air using the Lisle spill free funnel and running the car. No gurgling behind the dash.
    With the heaters on max I did after about an hour get slightly warm air during the bleeding.

    It's a UK car so no "thermos" but now no warm air at all.

    Could this be a clogged heater matrix?
    Does the A/C compressor also move coolant? One pipe is very hot going into the compressor, the other doesn't.

    The lower pipe from the radiator to the thermostat is getting hot. The radiator fan is coming on. The return to the radiator is also getting hot so water is moving and returning to the radiator for cooling, just not the cabin.

    I don't know if the heaters ever worked as it was summer so I was using the a/c that wasn't very cold, I assumed it needed re-gassed and haven't done that yet.

    Any ideas welcome as I'm stumped. And cold and it's not even winter yet :(

    UK Gen2 281,000 miles
     
  2. bisco

    bisco cookie crumbler

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    no connection with the a/c system. i suspect your heater core is shot, but i forget if there is a 3 way diverter valve on gen2, that would be worth looking into, although, i thought it threw a trouble light
     
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  3. Frijjj

    Frijjj Junior Member

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    Looking at this other thread, is it possible that the core pump has failed in my case? I've replaced the mechanical water pump and the invertor water pump. I don't have the thermos so no 3-way valve.

    If I was to disconnect the electric core pump and flush the disconnected electric core pump hoses would that go directly to the core and enable me to flush the core using a hosepipe to the house water main?
     
  4. sam spade 2

    sam spade 2 Senior Member

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    It is also possible.....and maybe likely even......that your wild guesses are in entirely the WRONG area.

    You NEED to find the hoses serving the heater core.
    If those are both hot after the engine warms up, then it is likely that you have an air flow problem and the dampers that direct air through the heater core are not working right.
     
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  5. Frijjj

    Frijjj Junior Member

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    I hadn't considered that. I will do some more investigations. I do have power to the fans and air blows from the vents. The windscreen will demist but it's cold air. Is there a fuse for the dampers?
     
  6. sam spade 2

    sam spade 2 Senior Member

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    Sorry, I don't know.
    In older designs, they were vacuum operated. I don't know if they are electric now or not.
     
  7. ChapmanF

    ChapmanF Senior Member

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    They're electric. That doesn't mean the reflex association of "electric" with "fuse" leads anywhere useful. You can watch their motions, though, while changing the heater settings (or even go into the heater test mode described in the repair manual, which will put them all in a range of programmed positions).

    Sometimes they need some cleaning, as covered here. In Gen 2 (at least in the US) there's a screw that's extra hard to reach because of an ECU that's in the way; yitznewton found a tidy way around that.
     
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  8. Frijjj

    Frijjj Junior Member

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    So just to update everyone in case someone else has this issue it is now resolved.
    I took it to an independent garage after I was unable to flush out the core. One pipe was warm and the other totally cold so it was a blocked core in this case. The garage was able to use pressure to flush the core and said a gel like substance came out. They suspect that two types of coolent were used at some point and they reacted causing the blockage.
    The heaters now work and all is good... so far!
    Thanks to everyone for the help and ideas
     
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