Honeywell 137980A
Test Button Mounts in Door of F50A F50E F50F F300

Test button assembly, mounts in the F50 F58 F300 door 203306AB and 203305AB. Also used in the F300E door 32007528-002 and 32007528-003.

Note F300 models built 2000 through 2005 came with a plastic door. These plastic doors do not support a test button 32004876-003 and 32004876-004.

Power Supply Bench Test

Here is our procedure to test the power supply. Warning high voltage shock can cause death.

The power supply has the option to disable the air flow sensor (see bypass AFS section). The AFS can be temporary disabled for testing by borrowing jumper from J8 to connection J3 position marked "bypass AFS". This power supply does not require the air flow sensor to operate. The photo below shows an older power supply that just needs 120v to power a cell.

Connect 120 vac to terminals P1 and P2. Check the following outputs with respect to chassis ground.

Terminal P3 will output 8.2k vdc
Terminal P4 will be 4.2k vdc
Terminal for the neon lamp outputs 100 vdc

Since high voltage meters are not common, Honeywell provides the neon lamp as reliable voltage indicator. If the high voltage output falls below spec the neon lamp voltage will drop out.

Shorting P3 or P4 to ground has the same effect as the test button. The short will temporarily cause the neon indicator to go out. By tapping P4 to ground you should be able to draw an arc 1/32". Tapping P3 to ground can produce a larger arc near 3/16". These tests are with out the cells connected, the arc will be twice the length with cells connected.

Honeywell power suply bench test

Fixing Cell Arcing

determining cell sparking areaIf a cell is sparking, determine the sparking area and removed cell to inspect closer. To see the sparking, you may need to look in through the blower compartment or cut an inspection hole in the duct. An inspection window can also be used to see if cells need to be cleaned.

A cell that is sparking randomly throughout is uncommon but could be caused by a film left behind from washing. If tobacco is not cleaned from a cell it can build up and cause random sparking. Diesel fumes can cause problems and are not easily cleaned. High altitude can make the air cleaner more susceptible to sparking. The collector plates should be cleaned to the bare shiny metal (stained is okay).

Major cell sparking can be the result of power box wires getting crossed. The cell is powered by two voltages. The ionizing wires receive 8kv and the plates get 4kv. If these voltages get crossed, then the cell will spark all over and much louder than normal.

If a cell is shorted and keeps the neon lamp from coming on, then inspect for damage. The most common short is from the aluminum dividers in between the ionizing wires. These dividers can get pushed in to the collector plates, they should not touch the plates. A dent across several plates causing them to touch would be a simple short to find. A dandling ionizing wire can cause a short.determining cell sparking area

Continuous Cell Arcing

continuous arcing by tabs contact with edge of every other platesThe 4074EHG tabs make contact with the edge of every other cell plate. Photo right shows the edges of the plates burnt down far enough, that the contact shorts against every plate and not every other.

Honeywell cells can last for decades, but continuous sparking can cause damage. A cell may spark continuous if collector plate spacing gets too close. The spacing can become uneven when a cell gets pushed out of square, twisted, a dent, etc.

One common problem is a loose plate that has lost the press fit with its horizontal rods. The loose plate likely had continuous sparking that created surges of current through the press fit. The current surges resulted in sparks that brunt away the press fit. This cell would not be repairable.

When one cell has been subject to excessive sparking, then both cells will be burnt under the contact pad. This is because a spark in one cell will cause a current surge that is drawn from both cells.

Check the contact pad to determine the condition of the cell. If your cells have badly burnt contacts as in the photo above, then it is best to replace the cells.

When a cell has been subjected to excessive sparking, the press fit of all the plates will first be weakened. The sparking at these connections causes corrosion from ozone. The aluminum around the press fit becomes corroded and no longer conducts as well.

The cell contacts operate at high voltage and are not a sensitive connection. The contact does not require cleaning. The contact is tin coated copper. Sandpaper will remove the tin coating.

The photo below shows arcing under the contact pad.

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