No heat

Hi- 2005 with no heat. I’ve verified mechanical thermostat, so now working on heater core circuit, specifically the electric aux. pump. I’m not clear which fuse controls that pump, however none are blown. Can anyone tell me which fuse? I’d like to jumper the pump to see if it’s running.

 

Thank you very much. It seems there is no or very low flow of hot coolant into the pump, as the hose remains cool, even though the input hose to 3-way valve is hot. I’m going to pull the wiper assembly tray and verify heater core is not plugged, as well as the pump and 3-way valve. In my case the problem seems to be coolant flow related. I’m not getting hot coolant through the core

 

Yes, thanks…. It has worked well for many years, and the valve was replaced a couple years ago…simply due to a code which occasionally would come up. heat just recently has become an issue. I suspect a blockage at electric pump or in the core.

 

I’m preparing to flush the heating system and storage container. I suspect there may be problems with heater pump. Can anyone tell me where the relay is for the HEATER pump? I’ve found the canister pump relay… is the heater pump relay in the same relay box on the wiper tray?
2005 Prius
Thanx

 

Well, yes… I found the wiring diagram. But I’m not able to figure out where the actual relay is physically located. It’s clearly listed in the wiring diagram as AC WP relay. But I apparently am not smart enough to tell from the diagram where to actually find it. I will go look at all the relays in various locations to see if I can find one labeled AC W/P

 

Yes, I’m quite convinced it is a coolant flow restriction. The hose going from 3-way to heater pump stays cool to Luke warm, even when heat is on max. Airflow is great. I replaced the 3-way last year.. it was occasionally throwing 1121 code. My plan is to flush everything in the engine/heater system and possibly replace the pump if it is bad or plugged.

 

I believe so…. It is the one which is routed around inverter and back toward firewall.

 

Ok- I understand….. yes, that’s how the relay is listed, on the inner circuit diagram. I think I can locate it now
Thanx

 

I’m preparing to tear into this heating issue and have some information to share. I found a good used heater pump, to use in the event mine is bad. It seems this is not a positive displacement type pump, so coolant passes through easily, even when pump is not turning. I did not realize this; for some reason I thought the pump runs whenever heat is turned on. So even if the pump dies, this should not prevent coolant from passing. This must mean there’s an actual block somewhere….or the valve is stuck. I’m going to start the investigation by pulling off the hose on valve which feeds the pump and blow thru it with radiator cap off to see if there’s a blockage….. just thought I’d share in the event anyone else is facing this mystery

 

Thanks everyone for your input- here’s an update: I pulled the hose from coolant control valve which goes to heater core.. I’m able to easily push air through with radiator cap off… so nothing blocked thru core. The problem is the 3-way valve, which I replaced last year due to a code … but no issue with heat. Now I have no heat and the valve is stuck. Stupid me… bought non-Toyota Dorman brand and it apparently only lasted a year. I bench tested the valve and it sounds bad/ sticks occasionally. This time I have Toyota OEM valve and will be flushing the entire ICE coolant system and doing the air purge dance, etc. hopefully this will get me back in shape..

 

I now have heat