the heater does not blow hot

It could be that hot coolant is not getting into the heater core or that the little door mechanism (under the dash and very hard to reach) which chooses the air source is stuck. I think either way that should set an error code but not necessarily light up the CEL. So get a decent code reader and have a look.

 

Have you already checked the coolant level in the radiator? (not just the white overflow tank)

 

Was that post meant to include a photo?

 

that might be it, or maybe the thermostat is stuck

 

Looking in the picture, I see a socket that is there, but does not have a relay plugged into it.

Have you looked up what a relay in that position is for? Has that socket always been empty?

 

Every year in Winter we get posts from people who think their heater won't work because they only drive their car short distances and it takes 15 to 20 minutes to get the heater performing at its very best when its super cold out.

 

there's a proceedure in the service manual i think. when we were kis, we used to put them in boiling water to see if they opened.

are all the hoses under the hood hot, after the engine has warmed up?

 

If the heater core sprung a leak a former owner might have chosen to bypass it rather than tear apart the dash to fix it. Trace the hoses in that region and see if they are stock. Search in these forums and you will find the diagram for what they should look like.

 

Is the coolant level IN THE RADIATOR full? Is the water pump drive belt on the engine in place?

That connector may have a relay that is missing, or your car may not need that relay. It should not affect the normal heater function.

Posted via the PriusChat mobile app.

 

Looks like you're missing a few relays there, try moving the only relay you have and see if something starts working (or fails to work).

Shouldn't there also be a larger grey relay in the box as well?

 

I'd be happier to see somebody look at a diagram of the relays that go there, and comparing to the trim level of the car and what options it has.

 

No.

Not necessarily.

For a 2007 Prius car built for sale in Europe (with model code NHW20L-AHEEBW on the certification label inside the left front door), the Electrical Wiring Diagram (more info) and Electronic Parts Catalog show that there might be only one relay in Engine Room Relay Block No. 2, just as seen in @Mehmet alb's photo: the blue RR FOG (rear fog lamp) relay, in the fifth socket from the left.

The socket on the left that’s different from the others, and the third and fourth sockets from the left, are indeed for PS HTR, PTC HTR 1, and PTC HTR 2 relays to control the electric PTC heaters, but those heaters and their relays exist only on versions of the car built for sale in the U.S. and in colder areas of Europe and Japan.

All versions of the car have a traditional heating system that circulates engine coolant. The relays for this are elsewhere on the car: the HTR (blower motor) relay is in the Driver Side Junction Block, and the AC W/P (heater water pump) relay is built in to Unit B (Integration Relay No. 1) of the Engine Room Relay Block.

For completeness, in Engine Room Relay Block No. 2, the second socket from the left is for the FR FOG (front fog lamp) relay, and the sixth socket from the left is for the CHS W/P (coolant heat storage water pump) relay—again, only if the car has these features. For all versions of the car, the relays in this block, if present, have Toyota part numbers 90987-02025, for the first socket, and 90987-02027, for the others.