2007 isl 400

[tgohal]

Behind my 400 ISL engine is a filter with a gauge attached to the top of the filter. The gauge hasn't moved since I bought the coach. Does anyone know what the function of this filter and gauge might be. Thanks!

[BigSkyBob]

Are you referring to the air cleaner restriction indicator?

[Cruzer]

Most likely the hydraulic filter. It reads how much restriction it has and is color banded with green and red zones. It'll only display while the engine is running. If it still doesn't display, it might be a bad gauge. They are kind of cheap and most of the time theget replaced because you can't read them through the plastic gauge lens any more.

If you change your hydraulic filter annually as per the service schedule it really shouldn't be getting plugged. You also need to change the strasiner inside the hydraulic oil reservoir every other year. If they plug up you'll get excessive restriction and the gauge will indicate that. Even with good filters though your gauge should show a bit of movement when running.

[Mr_D]

I've never seen a hydraulic filter with a restriction gauge on it, but this is only our 5th motorhome and I've only been RV'ing since 1957 so I haven't seen it all.
I think it's the air filter restriction gauge, press the rubber button on the bottom and it should reset itself. I do it every time I open the compartment.

[Cruzer]

All of the Tiffin DPs that I've seen have them and so does the Entegra that I reviewed. So far I've seen them on Freightliner, Spartan, and Powerglide chassis. Can't speak for Newmar.

Hydraulic gauges are regular 1.5" diameter rotary gauges. The air filter restriction gauge is a tubular sight glass with a resetable plunger in it.