Honeywell 4074EHG
Honeywell FC37 Series Collector Cell Contact Board

Honeywell 4074EHG contact board repair kit for FC37A Cell. Includes terminal board, 2 clips, 4 pop rivets and cell handle 137266. Overall board size 4½ wide by 4¼ high.

If your cell has the contact tab burnt in to the plate edges then the new contact board should be installed on the opposite cell end. The other end is identical but without the burnt edges.

The cell will now side in with correct air flow, but the old plastic handle will be at the wrong end. The new handle is provided so it can be installed on what is now the front-end.

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.

Cell Contains 3 Contacts but Only 2 Used

You may have noticed there are 3 contacts on the cell pad but only two contacts at the power box. This allows the F50-F300 to be installed with either right or left air flow. The cell can be rotated allowing an installation with opposite air flow.

Only two contacts are used, the center contact and one end contact. Photo animation shows when the cell is rotated, the contacts maintain the correct connections.

The center contact powers the ionizing wires. The two outside contacts are connected and power the collector plates.

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