A/C Heat only on Drivers Side

welcome!

that's a stumper. i don't have a layout, but it seems to me you only have one inlet. the air comes through a radiator core, and whatever temp is set, all the air is the same.
only thing i can think is fresh air is diverting the core somehow, but that makes my head hurt.
maybe someone more knowledgable will have a good suggestion, all the best!

 

sounds like a plan, sorry i don't have a better answer!

 

Hello,

i am currenlty having the same issue with my Prius. Was there any solution found to diagnose this issue?

 

Someone suggested a blocked heater core. To backflush it.
That means removing the wiper cowling, removing both heater hoses, and connecting a 3/4” hose to the upper heater core pipe. Flush lots of high pressure water.

 

I just flushed my heater core.
It’s 67*F outside.
The heater is set on high, recirculating, high fan, windows down.
The far left (driver) vent is 150*F (using a laser thermometer)
The center/left vent is 125*F
The center/right vent is 114*F
The far right (passenger) vent is 94*F.

When I switch to “floor”:
the driver feet get 95*F
and the passenger feet gets 85*F.

Please let me know if anyone figures this out.

 

Did you fix the problem yet? Same issue here. Blend door actuator is turning, temperature controlled actuator is turning as well. Flushed heater core still same.

 

Come again on which two actuators you mean? The "blend" one is the one that controls temperature (by blending together heated and unheated air in different amounts).

 

Sorry for replying late. "Blend Actuator" is working (moving) when temperature is changed. Another actuator (i don't know the name) moves when "mode" is changed (face / floor / floor+face).

passenger vent is always Cold.

 

That other one is the air outlet actuator.

I think the structure of the heater core is one big supply header along one edge, and one big collecting header at the opposite edge, with the coolant flowing through a bunch of independent parallel channels. (That as opposed to, say, a single tube with fins that would zigzag through the whole thing.)

So I think that if some of those channels were to get clogged, you really could end up with a heater core heating on one side and not the other. I struggle to think of many other ways that symptom could be seen.

 

since my heat is not working properly, I had kept to High and I got p261b. But then i stopped car and reset error. Drove another 50mile with no problem, coolant temperature stayed around 197 to 199.

Why i got P261b.

 

For anybody with a P261{B, C, or D} or P148F, get the engine water pump and its wiring checked and/or repaired promptly. Even if you can drive a bunch more miles on a dodgy water pump, it isn't guaranteed to end well.

The way the water pump's control circuit works is described here.

 

Water pump was changed recently. Should I check wiring?

 

Definitely. You can use the signal on WPI to check the pump RPM.

Who changed the pump, and where was the replacement obtained?

 

I bought an OEM pump from the dealer and changed it myself about 1500 miles ago. Only today i got the code when i ran the heat at 85.

When i reduced the heat to at around 77, i did not see any code.

 

I started the car, turned on high heat 85 and in 10 mins i got the error for the first time. Remember heat works on driver vent only

After the code, I switched to my old pattern (1500 miles since new pump) heat at 75. Coolant runs 197-199. No code. Came home without issues.

 

Hey im new here i have a 2011 does any one have a fix for this yet I have the same problem driverside is hot pass is cold no issue with codes or my water pump

 

Same here for my 2014. Just noticed it today. Hot on the driver side, no heat in the passenger side.
Maybe a heater core flush?

 

I flushed heater core (both ways) with water hose and used slimway, reconnected coolant line - still the same issue. I have a feeling its sucking in outside air on passenger side bypassing heater core.