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Fuel Gauge Reads Half Full

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kiitos
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Fuel Gauge Reads Half Full

Post by kiitos » Sun May 22, 2016 6:06 am

The boat is a 1948 U22. The fuel gauge reads only half full with the tank filled. The fuel tank sending unit is new. Actually I have tried two new senders made by two manufacturers. The senders are 33 ohm - 240 ohm, 12 volt. The sender has full motion in the tank. The fuel gauge was restored two years ago by Dale Kocian and changed to 12 volt although I do not know how to test the gauge to make certain it was swithed to 12 volt. The boat was completely rewired last year. Any ideas?
Mike
'78 Chris Craft 30' Sportsman
'49 Chris Craft 25' Sportsman - Twin "K"s

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drrot
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Re: Fuel Gauge Reads Half Full

Post by drrot » Sun May 22, 2016 7:10 am

Dale usually marked them on the back.
Make sure you have a good ground.
Jim Staib
www.finewoodboats.com


1947 Penn Yan 12' Cartopper WXH474611
1950 Chris-Craft 22' Sportsman U-22-1532
1957 Chris-Craft 26' Sea Skiff SK-26-515
1968 Century 17' Resorter FG-68-174

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mbigpops
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Re: Fuel Gauge Reads Half Full

Post by mbigpops » Sun May 22, 2016 8:13 pm

Since fuel gauges read current it would make sense that the voltage will impact the gauge reading.

Using V=IR then I (current) = V (voltage) / R (resistance)

In your case with 12V, I=12/33 ohms = 0.36 Amps. If you were 6V then I=6/33 = 0.18 Amps

I am thinking that if your gauge was setup for 6V you would see the opposite problem - since it is sending a higher current reading it would read full when it is really half full.

Sounds like you have another issue - maybe the wrong sensor type ?

Mark
1953 CC Rocket Runabout "Rocket Man"

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Re: Fuel Gauge Reads Half Full

Post by sproat3 » Sun May 22, 2016 9:32 pm

Mike-
The 33-240 ohm sender you have is standard today, but the sender units in the older boats had different resistance ranges so your fuel gauge may be calibrated for a different resistance range.
Search under Electrical for Riviera Fuel gauge resistance for a thread on this topic from a couple years ago. I had a similar problem on my 1960 Capri and I described there how I fixed it.
Ward
1960 Chris Craft Capri (Tahoe Heidi)

kiitos
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Re: Fuel Gauge Reads Half Full

Post by kiitos » Mon May 23, 2016 5:43 am

Ward, Mark & Jim:

Thanks for your input. The first new sender I purchased was from Rayco Tanks. Under the former ownership of Rayco I had a tank built for the '47 17' Deluxe Runabout that I was restoring. The fuel gauge had been rebuilt by Dale K. Everything worked perfectly.

This boat is a '48 22' Utility. The boat's electrical system had been upgraded to 12v but the fuel sender was still 6v. So I went back to Rayco which had been sold to a restoration company in Kentucky and bought a new 12v sender. They assured me that the sender was the same brand sender that the Rayco Company had used for years. Rayco was very willing to help me solve this problem. They sent a new sending unit that I checked against the one I had purchased and I tested both with an ohm meter. Both senders tested identically with the ohm range of 33-240.

My next step is to put the gauge on the bench and use a potentiometer to test the gauge. I will post how I eventually fix the problem.

Thanks.
Mike
'78 Chris Craft 30' Sportsman
'49 Chris Craft 25' Sportsman - Twin "K"s

Tightline5
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Re: Fuel Gauge Reads Half Full

Post by Tightline5 » Mon May 23, 2016 6:52 am

I had the same problem with my gauge from Kocian's this year????????? I called Clawson after much frustration. Here is how you check the gauge and tank. First check the OHM reading between the sending unit (resistance) from the gauge with a full tank. Is it 240 OHM or 33, a full tank will have the lowest OHM. Then with the ground, sending wire, and power wire disconnected from the gauge check OHM reading on each stud. The sum of two stud readings should be the sum of the third. I later- found that after having my gauge re- repaired by Kocian's, the guy who installed the gauge in my tank installed it backwards, and that is why the repaired gauge is reading 1/2 full on mine.
ALL ELSE FAILS CALL Clawson Instruments, but sounds like the sending unit to me.
Phil Jones

1948 US Plywood Executive Runabout Hull #1 "WeldWood"
1954 Racing Runabout R-496
1957 Deluxe Runabout D-17-2062
"MISBEHAVIN"

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Re: Fuel Gauge Reads Half Full

Post by jim g » Mon May 23, 2016 4:54 pm

Clawson has the correct sending units to much the old gauges. Ward is correct. The senders for the old boat gauges are a different resistance range.

kiitos
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Re: Fuel Gauge Reads Half Full

Post by kiitos » Wed May 25, 2016 5:59 am

Sending Unit is the culprit. It was Mark Clawson to the rescue. I was very impressed with his response. He answered my inquiry in just a couple hours with a very indepth analysis on how the system works and what it takes to resolve the problem. The sending unit that my Chris Craft gauges use requires a different ohm spread than the 33-240 than the sender I was sold by Rayco last year. Thanks to everyone that replied.
Mike
'78 Chris Craft 30' Sportsman
'49 Chris Craft 25' Sportsman - Twin "K"s

kiitos
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Re: Fuel Gauge Reads Half Full

Post by kiitos » Wed Jun 15, 2016 6:24 am

Sending Unit was not the culprit afterall. Mark Clawson sent me a new sending unit that I fortunately tested before going through the headache of installing in the tank. The gauge then read 3/8 at empty to full. The opposite of the original problem. Mark offered to let me return the sender for credit and asked me to send the gauge and he would check The gauge calibration. I mentioned to Mark that the gauge had been refurbished by a very reputible restorer two years previous but he mentioned that it is not uncommon to have a problem even though the gauge had been restored. I sent him the gauge and he reported back that the gauge had already been set up to accept 12 volts and also to match with a 33 - 240 ohm sender which was I already had in the tank but the gauge was very much out of adjustment. Mark spent a considerable amount of time calibrating the gauge and sent it back to me only one day after receiving it. Now the fuel gauge reads as it should, problem solved. Kudos to Mark Clawson at Clawson Classic Instruments in Anacortes, WA!
'78 Chris Craft 30' Sportsman
'49 Chris Craft 25' Sportsman - Twin "K"s

Tightline5
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Re: Fuel Gauge Reads Half Full

Post by Tightline5 » Wed Jun 15, 2016 7:01 am

I to had the same problem with that "well known" gauge restorer, and Clawson came to the rescue. Clawson will get any work I have in the future.
Phil Jones

1948 US Plywood Executive Runabout Hull #1 "WeldWood"
1954 Racing Runabout R-496
1957 Deluxe Runabout D-17-2062
"MISBEHAVIN"

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Jim Godlewski
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Re: Fuel Gauge Reads Half Full

Post by Jim Godlewski » Sun Jun 19, 2016 6:45 am

I was disappointed when Dale moved on.... I'm currently in the market for three fishscale gauges.
Glad to hear you got it squared away.
1956 17 Sportsman CC-17-2310
1930 Model 100 7152
https://1956chriscraftsportsman.shutterfly.com/

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