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Heater Matrix Hoses - check correct flow


Tom777
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Hi All,

I’m looking for help from someone who can confirm that my hoses are connected correctly from engine bay to heater matrix. Please see picture for reference. This is a UK model Lexus Is250 2007.

I have issues with heat in cabin and want to rule out incorrect hose connections from previous ownership/services. If someone could compare against their own IS250 that would be great. Looking at the picture is it correct that the blue line lower hose from engine should be connected to the inlet on the left inlet passenger sid. So blue lower hose goes to left inlet and upper red hose goes to right side inlet ?

Best thing is if someone actually could check against their own car. I don’t need help with other things explaining my heat in cabin issue. I am aware of all the other things it could be but want to rule out this factor also. 
Im basically getting less heat on passenger side/nearly cold air while driver side is normal with heat.  Want to rule out incorrect hose connections. See picture.

thanks  

26BA9A70-7FD5-4557-837C-9FB978B17679.jpeg

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As you can see on picture from Uk heater matrix the left inlet from engine bay runs into top of heater matrix and right side outlet in engine bay is from bottom of heater matrix. I’m wondering if it matters what way the flow goes. I could think that the top red hose from engine bay should run into left inlet to flow to top of heater matrix. And then the outlet from heater matrix should be the right outlet flowing into the blue lower hose back into engine. Not sure what the logic/physics should be for the flow. 

39A43A72-74F2-44E0-BAE8-CBF1B0981C27.png

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1 hour ago, Alfalfa said:

Hi, some pictures of my car and 2 pictures of my oil catchcan installation.

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Thanks looks like you are in a left hand drive car. I’m in a right hand drive car and not sure if the heater matrix is turned the same way in yours - meaning the blue line is running to the the bottom inlet of the matrix. 

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Thanks looks like you are in a left hand drive car. I’m in a right hand drive car and not sure if the heater matrix is turned the same way in yours - meaning the blue line is running to the the bottom inlet of the matrix. 

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Nah. The matrix seems to have the same flow and design no mater if it’s LHD or RHD so that doesn’t seem to be the problem. Need to take the matrix for a flush to see if this will resolve the issue with low heat on passenger side. It’s not the actuators etc as this is all spinning nicely. 
very frustrating issue to have with a luxury brand car. 

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59 minutes ago, ColinBarber said:

Here is the flow diagram

image.thumb.png.d01467703c3cfe44051d7e7a2738bb4e.png

image.thumb.png.47f4ea4ecccb8319e9cc3eca808d9e81.png

Yes this also confirm what I read. The radiator has flow top down while heater has flow bottom up. Thanks. My culprit is not wrongly connected hoses. Just wanted to make sure.

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  • 11 months later...

No I have basically given up. I am still to take it to a specialist to flush the heater core as I live in flat and don’t have the equipment to give it a try myself. But a heater flush would probably also mean I have to get coolant refilled again - topped up to avoid air bubbles and what have you not. This issue is a real pain and a weakness in the IS250. My issue has nothing to do with the flaps and all that in the cabin in case anyone jumps on here and starts talking about that again. It’s very annoying. I am sure I bought the car with that fault. seller aware but did not mention as I only checked the air condition which works great but heating is the issue. Who would expect that. Always check the air condition and heating in detail when looking at an IS250. I will update if a flush helps but probably won’t do that before next year. I can still keep the car warm with just the right side heating but the problem is that front passenger gets cold with the cool air blowing etc so have to close the air outlets on left side completely during winter driving. It’s ****** ☹️

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  • 9 months later...

2 years I have studied my issue with not getting any heat on passenger side on a UK car. I am very proud to have solved the issue myself. Look what I created (fire: movie: Cast Away).

I had to put the Techstream software on it to perform: INITIALIZE SERVOMOTOR. This is a utility/function provided by the Toyota Techstream software - used as per MANUAL when Battery has been replaced or disconnected or servomotors (blend doors for USA) have been replaced. Imagine, some advice on the web is to disconnect Battery when you have this issue with not getting hot air on one side or uneven temperature between the two sides. The exact reason why you might get this issue in the first place. It’s bloody fixed-  It needed actual recalibration, not bleed air, not heater flush, not new actuators/servomotors, not new sensors, not advise “have you tried to adjust dual temperature settings”, lol… and this and that…. 

It was a calibration functionality for AirCon in Techstream that fixed it. I win and me and only me found the solution, not my local mechanic, not some redneck, but me.  I’m joking friends. But it’s fixed now, and I hope this helps anyone in the future who is about to give up life and their Lexus. Never give up on a Lexus!

NOTE. Not all toyotas and Lexus have this Techstream option: “Initialize Servomotor” option, but my IS250 2007 did. Do your own research regarding models. I spend £150 before I found the solution. Don’t spend £700 on a heater core replacement with your local mechanic before this step as per Lexus manual has been implemented. Your local mechanic might know nothing of it but your Lexus Dealer might do - hopefully. Initialize Servomotor

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