How To: Dash Blend Door Actuator Replacement 05-09 Mustang

Thanks Dino. Changing out the center upper (1870) as soon as it comes in. Thank god it wasn't the driver's side.

Gray write up! Guess it’s my turn to tackle this job and I think I’ll just change all four. Started out with the “clicking” when switching from defrost to vents but now the driver side doesn’t blow cool at all. Figure I can’t get it wrong if I change them all. Now that we’re approaching the misery that is gulf coast warm weather, it’s time.

"13. Use a pair of needle nose pliers to remove the two 5A fuses as indicated by the arrows (fuses no.10 & 12 in diagram). These control the HVAC system and the fuses need to be left out for at least one minute to reset it properly.

To ensure correct operation of the new actuator, the HVAC system needs to be reset. This step is VERY important so don't skip it."

Dino, if I remove battery power does it take care of this step or must power be present and the fuses removed to accomplish the step?

white95 said:

Gray write up! Guess it’s my turn to tackle this job and I think I’ll just change all four. Started out with the “clicking” when switching from defrost to vents but now the driver side doesn’t blow cool at all. Figure I can’t get it wrong if I change them all. Now that we’re approaching the misery that is gulf coast warm weather, it’s time.

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*great

DieHarder said:

Dino, if I remove battery power does it take care of this step or must power be present and the fuses removed to accomplish the step?

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Disconnecting the battery should also do the job but since this will also reset the main ECU, you'd also need to perform the idle relearn procedure as per the instructions in the owner's manual.

Dino Dino Bambino said:

Disconnecting the battery should also do the job but since this will also reset the main ECU, you'd also need to perform the idle relearn procedure as per the instructions in the owner's manual.

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Dino, not sure what that is. Never have had to perform it. I have a DOB setup w/a Lito tune. Been running great for a couple of years now. I regularly disconnect the battery due to a EO/KO current drain that I haven't quite identified the cause though I suspect it has to do with LEDs that I added for map lights. Takes a couple of weeks to completely drain and has destroyed two batteries so far. So if I'm going to have it sit for more than a week (winter comes to mind) I disconnect the negative lead and put it on a smart charger. Been like that for over a year now. Thinking of changing out the LEDs for standard incandescent to see if that changes anything.

DieHarder said:

I suspect it has to do with LEDs that I added for map lights.

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What makes you suspect the LEDs?

Since they are diodes, they only allow current to flow in one direction. If current is passing through them constantly, I would expect them to glow.

If they work properly when energized, and go dark when switched off. I can’t see that being the problem.

Just thinking aloud here…

Anyway, sorry for my off-topic reply Dino.

Mine are cheap. Likely "leaky". It's one of the few circuits that's also tied into the door sensors and controlled electronically whenever a door is opened. Everything else that I have LEDs on (front halo's; headlights; rear markers; USB power ports) are controlled by physical switches that must be operated by hand before power is sent to them. Only other thing I can think of that's on all of the time is the security system which is a possibility though it's a Ford dealer upgrade but I don't believe it's the issue because I never had to worry about the current drain prior to replacing the map lights w/LED's.

Changed the “Temperature blend door actuator” in hopes that it would blow cold on both sides again but no such luck.

Looks like I’ll be changing all of them.

Fought the one behind the instrument cluster today and…


…no change!

At least the last two are easier to reach!

Me again..

Changed all four at this point and it’s still not cooperating. It does blow a helluva lot harder than before and the chattering/clicking when switching from defrost to panel is gone. Worth noting the compressor cycles on/off roughly every 8-10 seconds. It does get a little cooler with engine speed.

When we swapped cams earlier this year, we changed the line with the high pressure port because the valve was slowly leaking by. Pulled it under a vacuum for a hour or so and it held fine. Do not recall how much Freon we used but I want to say 32ish Oz. Read in another thread that these cars don’t take that much. Fml.

If your compressor is cycling that quickly you might have an issue (I.e., low Freon or an obstruction).

Put A/C gauges in and see where your Low and High side are at…

white95 said:

Me again..

Changed all four at this point and it’s still not cooperating. It does blow a helluva lot harder than before and the chattering/clicking when switching from defrost to panel is gone. Worth noting the compressor cycles on/off roughly every 8-10 seconds. It does get a little cooler with engine speed.

When we swapped cams earlier this year, we changed the line with the high pressure port because the valve was slowly leaking by. Pulled it under a vacuum for a hour or so and it held fine. Do not recall how much Freon we used but I want to say 32ish Oz. Read in another thread that these cars don’t take that much. Fml.

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Does the fan cycle with the compressor? Is your radiator fan running constantly while the AC is on? If not your low speed fan resistor is blown and you only have high speed available. Without the fan on the AC compressor will overload and turn on the high speed fan to cool it and cycle like you described.

Robert Larimer said:

Does the fan cycle with the compressor? Is your radiator fan running constantly while the AC is on? If not your low speed fan resistor is blown and you only have high speed available. Without the fan on the AC compressor will overload and turn on the high speed fan to cool it and cycle like you described.

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I will check this and report back.

JC SSP said:

If your compressor is cycling that quickly you might have an issue (I.e., low Freon or an obstruction).

Put A/C gauges in and see where your Low and High side are at…

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After this, I put 18 Oz of Freon in and it blows cold again. Definitely has a leak.

Is A/C compressor still cycling erratically?

JC SSP said:

Is A/C compressor still cycling erratically?

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No, it’s functioning properly. If/When it begins to act up again, I plan to UV/dye check for leaks. We had it apart last April and it started blowing warm by late fall. Should only be a matter of time.

white95 said:

No, it’s functioning properly. If/When it begins to act up again, I plan to UV/dye check for leaks. We had it apart last April and it started blowing warm by late fall. Should only be a matter of time.

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Ford uses UV dye in the gas for all its cars AFAIK. My 2012 had a leak in a line coming out of the compressor that I found with a UV light. I replaced that line and have been good ever since and that was over 8 years ago. Ide get a light and start looking you may be lucky like I was.