What The Filter Does
This is a panel-style cabin air filter built from pleated filter media. It sits ahead of the blower in the fresh-air intake path and catches dust, pollen, road soot and insect debris before that load reaches the evaporator core and the cab. It is not an engine air filter and it does nothing for oil or fuel side filtration.
The pleats matter. Pleating gives you more media surface in the same frame footprint, so the filter holds more dirt before restriction climbs. That keeps blower output where it should be. A flat, low-surface panel loads up faster and starts choking airflow long before it looks dirty to the eye.
Symptoms of a spent filter are predictable. Blower speeds feel weak on high, defrost takes longer to clear glass, and the cab smells dusty or musty when the fan first kicks on. Drivers on gravel yards, feedlots and construction sites will load one of these far faster than a highway truck running paved lanes.
Why These Numbers Cross
AF26235, P609422, P-CF6654, 91559, BO91559 and the Alliance numbers ABP N10G 91559, N10G 91559 and N10G 91560 all describe the same physical panel: same media type, same frame envelope, same orientation in the Freightliner HVAC housing. Different sellers and different catalogues index the identical filter under their own house numbering, which is why one part shows up under eight strings.
The prefix and suffix noise on the Alliance side is the usual cause of confusion. ABP N10G 91559 and N10G 91559 are the same core number with and without the branch prefix, and 91559 versus BO91559 is the same story from another catalogue. Strip the prefixes and you are looking at one filter, not four.
Donaldson P609422 and the P-CF6654 reference are filtration-house catalogue numbers for the same panel. Cross-reference gets you to the right family fast, but it is a starting point, not a fitment guarantee. Confirm against the number printed on the frame of the filter you pulled out, or verify by VIN, before you commit to a case quantity.
Check Before You Order
Pull the old panel and read the frame. Most cabin filters carry a legible number on the cardboard or plastic edge, and that number is the most reliable thing you have. If the frame is soaked or shredded, measure length, width and depth before ordering, and note which way the airflow arrow points so the replacement goes back in the same orientation.
Watch for previous repairs. Trucks in this family have been in service across a wide model span, and it is common to find a trimmed filter, a doubled-up panel, or a housing with a cracked retaining tab from a past service. A damaged housing will let unfiltered air bypass the media no matter which filter you fit.
AF26235 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to AF26235. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cross-Reference | P-CF6654, 91559, BO91559 |
| Alliance | ABP N10G 91559, N10G 91559, N10G 91560 |
| Donaldson | P609422 |
Frequently asked questions
Is AF26235 the same filter as Donaldson P609422?
They cross to the same panel filter in our catalogue. The numbers come from different cataloguing systems for what is functionally the same pleated cabin air filter. Verify against the number on the filter you removed, or by VIN, before ordering in quantity. We list other manufacturers' numbers for identification only.
What is the difference between ABP N10G 91559 and 91559?
Nothing on the part itself. ABP N10G 91559 carries a catalogue prefix that the shorter 91559 listing drops. BO91559 and N10G 91559 are further variants of the same core string. All of them point back to the same cabin air filter panel.
How often should this cabin filter be replaced?
Service interval depends entirely on the environment the truck works in. Highway trucks on paved lanes go considerably longer than units running gravel yards, feedlots or construction sites. Inspect it at every PM, hold it up to a light, and replace it when the pleats are packed or blower output has dropped noticeably.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.