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Delanair MkIII issue, initial pulse of air then nothing
Hello, sorry for the lengthy post but I tried to include recent history and fixes I’ve tried so far.
I'm looking for some help with an issue that's started with my Delanair MkIII hvac system in my series 3 V12. When I turn the mode control switch (the one with choice of off, low, normal, high, defrost) from off to any speed, I'm getting an initial pulse of air from each side (both blowers) for about a second before the system stops doing anything. At that point there is no fan operation or air movement at any speed including defrost, in either manual or auto setting, and regardless of the temperature setting. The a/c compressor clutch does engage when I turn it from off to any speed. I currently have the temp control at the cold end of the range - it's still pretty warm her in Ga.
If I turn the mode switch to off again, and then to any speed, the same thing happens again, a pulse of air from each side and then nothing. I thought I recalled seeing a post on this particular issue in the past but couldn't find it after a search.
I checked all of the fuses in each footwell including the 50 amp (or 35 amp?) blower fuses and those were good. The MkIII written materials I have also mention an inline 3 amp fuse at the “right hand footwell outlet’”. I checked the only fuse I could find in that area - see my photo - but no joy. Anyone know of this is the ecm fuse? Does the fact I'm getting that pulse of air and the compressor clutch is engaging indicate this isn't a fuse problem?
Some additional recent history: I removed both blower motors and had them rebuilt and then I reinstalled them recently. At the same time I swapped in a used but known to be working (recently at least) ECM that matched the old one in model number. I drove the car a few times and everything worked as it should and the rebuilt blowers were moving a lot of air. This issue developed on the 3rd drive. I did notice that when I turned the system on I would get that initial pulse of air and then the blower fans would slowly come up to the fan speed it was set on.
The reason I had installed the replacement/used ecm was because with the old one I was only getting high speed fan action regardless of the settings, even after the blowers were rebuilt.
I tried swapping in the original ecm again and with that one I’m not getting the initial pulse of air or anything.
So do I need to just start going through testing the 45 pins and the checklist? Any other ideas? Thanks ver much.
09-23-2022, 04:25 PM
Delanair MkIII issue, initial pulse of air then nothing
