Improving cab air in a John Deere 6620 combine

I was reading earlier in the week on some other forum (old post) that a guy recommended taping or plugging a cab filter in the John Deere 6620 combine cab to improve the cab air quality. He said if you did this the cab air would be as good as the 9400 / 9500 / 9600. I assume it would restrict "new dusty" air from coming in and just continually filter the existing cab air. Can someone tell me what this guy was saying to do and how to do it???? I have a new cab filter and the tray/seals seem good. Just interested in what this guy said. Thanks.

IMHO, without a continuous inflow of filtered outside air the keep a positive pressure in the cab it will get darned dirty from dirt filtering in through every little crack and control opening.

Probably ok with 100% recirculation as there will be plenty of air leaks for fresh air .

(quoted from post at 07:50:36 09/30/17) I assume it would restrict "new dusty" air from coming in and just continually filter the existing cab air. .

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I have never heard that idea. I would say if you are getting dusty air coming in then your cab filter is not doing it's job. They stop dust but if you drag a lot of dirt and chaff in on your boots it will dry up and re-circulate around the whole cab. Keep that outside air coming in through the filter and it helps pressurize the cab. Unless you have some major holes in the cab. (or a window open which defeats the whole purpose of a cab fan and filter anyway).

Back in the 70's we had a Massey 510. The cab air filter would plug up quickly. Dad cut a hole in the left front corner of the cab in the top. He made an adapter and installed a engine precleaner to the cab. He covered the old air intake with duct tape.

The cab air then went through the precleaner then the filter. It made a real difference.

You need the outside air to pressurize the cab. This is what keep more dust out of the cab.

If your getting lots of dust in a 20 series cab then you have some thing wrong:

1) First remove the plate on top of the cab. This covers the evaporator and heater cores. Clean everything up real well with compressed air and vacuum cleaner. Then make sure all of the hoses are sealed where they come into the box that has all of the AC/HEAT components in it. Then make sure the gasket is good between the cover and housing.

2) Door seal condition and fit. It they are rock hard they will not seal. If the door latch is not adjusted right the door will not fit the opening correctly.

3) Pull the dash out and make sure all the grommets and sealing material around the wiring harnesses are good.

4) Inspect the gear shifter boot. They stick down in side and they seem to attract mouse holes.

5) Look at the rubber seals around the tilt steering column. They get stiff with age and do not flex into place like they should.

6) Check the fit and condition of the power shaft cover that your setting on. LOL The rubber seals around it often get damaged when working under the seat. Also seem to attract mice.

IF you do this your cab will be as clean as any JD cab out there. The trouble is the newest JD 20 series cab is 28 years old. Lots of little leaks mean the cabs get dust in them.

I have a JD 1989 6620 Side hill combine. It is one of the last twenty ever built. It has 2200 hours on it. Several years ago I spent 2-3 days doing what I just explained to you. The cab stays clean now.

P.S. Make sure the fan motors are running at full speed and that the blower wheels have all there fins. IF either of these two things are not right you will not have the pressurization you should and you will have a dusty cab.

Yep, after I posted my question this morning I realized that it would take outside air to pressurize the cab. I will take the cover off of the evaporator and heater core tomorrow. Also need to get in there to check if the evaporator is filled with chaff as I am not getting as much cold air as normal. Might need a charge on the air conditioner.