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Heater only blowing hot air when temp set to 'hi'

Phg

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Northampton
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Honda Accord 2.2 Ex
Hi,

I have a 2006 Accord exec (diesel) which only blows out hot air when the temp is set to 'HI', even if I reduce the temp to 28 it starts blowing out cold air. This issue has only started happening after my mechanic replaced the top steering pipe. Could the two be connected?

I have spoken to the mechanic who states that it may need 'bleeding out'....Having done a bit of research, im not completely convinced this will resolve the issue. Has anyone else had this problem, if so how did you resolve it?

Thanks
 
He may have dislodged the cable to the valve on the heater matrix, which is now probably stuck in the off position.

I'll dig out some pictures .....
 
With target temperature set to HI the valve should be as in the picture below (it's on the bulkhead at the back of the engine, note that this pic is from a 7th gen petrol Accord)

IMAG0555__zps0f8598e7.jpg


With target temperature set to LO the valve should be as in the picture below
IMAG0556__zpsffadb3f7.jpg


If that valve is not moving, that is why the heater is cold (***uming airflow is not blocked and engine is at operating temperature)
 
btw, try getting an ***istant to move the temperature setting between HI and 28 while you are looking at the valve, if it stays in the open position get the ***istant to keep ramping the temperature setting down until the valve shuts, then ramp back up until it opens, and make a note of the temperature setting when the valve changes position.
 
When the target temp is set to Lo or Hi the valve is in the position as the photos above. However when the target temp is set to anything other than Lo or Hi the valve simply stays in the position of Hi. The valve changes position from Lo to 16.

Would this suggest this suggest the cable has been dislodged and stuck in the off position?
 
Do you mean like this ?

Hi - valve open (top photo)
28 - valve open (top photo)
27 - valve open (top photo)
26 - valve open (top photo)
25 - valve open (top photo)
24 - valve open (top photo)
23 - valve open (top photo)
22 - valve open (top photo)
21 - valve open (top photo)
20 - valve open (top photo)
19 - valve open (top photo)
18 - valve open (top photo)
17 - valve open (top photo)
16 - valve open (top photo)
Lo - valve closed (bottom photo)

If so, then the heater matrix might be blocked, or, it might be low on water (check the engine water level when the engine is cold), or, the engine might be running cold (faulty engine thermostat)
 
You can look at the engine temperature (and other things) by using the built-in diagnostic (click on the image to enlarge)


SEA3E50K71100000000BBAT00_4.jpg



The only "difficulty" ergonomically speaking is that, when in diagnostic mode, you can't see the "target" temperatures in the upper display. This is because the upper display shows the value from the selected sensor instead.

Best thing is to practice "blind" setting the target temperatures when in normal mode i.e. start with the target in LO then count how many presses of the red "up arrow" it takes to get to HI, so that you can set any desired target temperature "blind" by counting the up/down presses from LO. Then set the target temperature to LO, switch off the engine, follow the instruction in the image above, then set the temperature by counting the presses of the "up arrow".

You can drive the car while the system is in diagnostic mode and look at any sensor.

In particular, look at the temperature sensor readings (sensors 1, 2, 4) and see if they are "reasonable". Sensor 4 (engine temperature) should reach about 80 C.

For "sensors" 6 and 7, as you change the "target temperature" (blind) you should see the flap % change. This is important because the flap % indicates the mix of hot and cold air that the controller is trying to achieve.

Sensor 5 should be about 5 C with the aircon ON. With aircon OFF it should settle at ambient.

Sensor 9 is strange, I think it is "virtual", and is a function of "target temperature" minus "in-car temperature"
 
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