Rochester Fuel gauge 'conversion capsule' quit

23coastal

Seaman Apprentice
Joined
May 31, 2008
Messages
37
A bit wordy but descriptive.. 1996 Wellcraft Excel (Coastal 23) Electric gauge at the console shows empty, but the mechanical gauge at the tank is accurate. I have a swingarm mechanical type of sending unit in a 99 gal gas tank. The unit has an electronic 'capsule' that shows the fuel level at the tank and the electric console mounted gauge. I crossed the wires at the tank and the console gauge pegged. Zero ohms or an open was metered between the spade terminals on the conversion capsule. So at this point I am convinced the problem is the conversion capsule. I brought the sending unit to a local marine shop where we installed a replacement conversion capsule. The conversion capsule read a half a tank when the swingarm float was at its lowest point. The conversion capsule read full when the float was at its highest point. Now im guessing that the new conversion capsule may not be compatible with the sending unit or the new conversion capsule is broken out of the box. Both capsules are made by Rochester. There are a few differences between the new and original conversion capsules. The new capsule has red and black wires connected to spade terminals. The spade terminals are directly attached to the original capsule. Also the underside of the new capsule has two small round metal pieces. The underside of the original capsule has a what looks like a black washer looking disk. See pic of original capsule (before it was cleaned up and metered). Any clues?
 

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NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
Re: Rochester Fuel gauge 'conversion capsule' quit

Never heard of a "conversion capsule" nor seen a setup with a gauge on the tank like that, so I can't help you there. But I don't see a ground wire going to a sending unit mounting screw, which your dash gauge needs if the system functions the way regular ones do.
 

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Rochester Fuel gauge 'conversion capsule' quit

The Conversion Capsule should read from 33 to 240 ohms.
Not ZERO or OPEN!

Red wire goes to original Wire to dash.
Black wire goes to ground.
Your tank looks to be metal so that was the original ground for the original capsule.
 

23coastal

Seaman Apprentice
Joined
May 31, 2008
Messages
37
Re: Rochester Fuel gauge 'conversion capsule' quit

Thanks for the feedback. Agreed, the conversion capsule needs to be replaced. When I placed a new conversion capsule in the keyed sending unit the gauge on the capsule read about half when the float was at the lowest point (should have read empty) and read full when the float was at the highest point. I found only one type of Rochester replacement conversion capsule. Does it sound like the replacement capsule is not compatible with the mechanical sending unit or is the replacement capsule defective? The store had only one in stock.
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: Rochester Fuel gauge 'conversion capsule' quit

For my 23' Wellcraft (122 gallon tank) I called the tank manufacturer as indicated on the data plate next to the sending unit and ordered the factory replacemant.
 
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