Air Filter Minder maxed out all the time

[Tony Lee]

During our first four month trip after buying the MH I noticed the filter minder was right on maximum so decided I''d better change the filter even though I had paperwork that showed it had been changed at great expense (to the previous owners) by a proper workshop.

They did a really classy job on it to the extent that the air intake tube (that collects the dusty air from just above and behind the rear wheel - thanks airstream, Really smart design) wasn't even clamped to the air filter inlet tube - and we had done a lot of miles on dirt roads.

Aha I said to myself. That's the reason. Slack mechanics!!

So in a carpark somewhere in some town - where I do all my maintenance - I struggled mightily to get at the mountings and clamps and finally managed to swap the filter for a new one and got the air intake firmly clamped and added a few wraps of duct tape for good measure.

I was mightily annoyed to find after a burn around the block that the filter minder was much higher than I would expect for a brand new filter.
Anyway, it is all back together and I sure as heck wasn't about to take it all apart again to investigate.
Put it down to a faulty filter minder and drove on. Next year we went to Alaska and back and this year down to southern Mexico and back. Performance hasn't varied and fuel consumption hasn''t changed either. Reset the minder and next day it is at max again. Must be faulty. MUST be!!!

Anyway - today I bought some 1/4" tubing and a tee and checked the calibration by sucking water up out of a bucket - and lo and behold, when the water column is 25" high, the minder hits the stops.

So the minder is accurate to half an inch of water, the MH runs OK and supposedly the filter is blocked solid.

What is going on?????