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karmannghias.org Blog for the Alken D2 and Sonett 3


Day 52 – Monday April 6

Posted in Sonett III by Administrator on the April 10th, 2009

We spent some time on the fuel sender today. After some emails back and forth with Palo Alto speedometer we decided to simlutae the resistance value of the sender to make sure the gauge would display correctly. Here are some notes on what we found.

Fuel sending unit uses three wires:
black for ground – tank to body
brown for low level light – W terminal
gray for the level – terminal G

Gas Guage test:
Pull gray wire, leave it open, and turn on key, gauge should show full
Ground gray wire and turn on key, guage should show empty
Pull and ground brown wire, turn on key and red low fuel light come on

Hook 1K, 10 turn resistor between gray wire and ground. At 10 ohms the gas guage should just start to move, turn it up to 200 ohms it should peg at full.

Sender test:
Pull gray wire from G terminal on sender and leave open
Empty tank should read about 10 ohms, meter connected to ground and “G”
Full tank should read about 200 ohms, meter connected to ground and “G”
Level in between should be 10 to 200 ohms

Palo Alto couldn’t easily determine the ohms from the level sender data punched into the top of it. This is why Adam and I used the resistor to tell them the actual values. They believe a 10-180 ohm unit will work. The manual listed two part number so maybe some gauges are different.

LATER WE FOUND IT TO BE 12-178 OHMS IS A STANDARD UNIT. 12 ohms put our needle about 1/2 of the way up the red, and 178 ohms just reached the full. We told them to go ahead with the rebuild.

It looks like the low level warning is some type of contact switch to that when the level is low the brown wire grounds which in turn lights the red low level light.

The cost of the rebuild since our reistor was open will be about $200.

Here is a resource from on-line that is a good explanation of how the gauge works.

Sending Unit

In the drawing below, we simply put the 1 K resistor in the cirucuit in place of the fuel sender. When you want to measure the resistance fo the pot, you have to take it out of the circuit (remove the at least one wire) and measure across it to know the reading. We did this to confirm that the standard 12-178 ohm sending unit resistor would work.

We took some measures for the fuel sender and sent them over to Paso Speed Shop

Hi Hartmut,
Here is what Adam and I found, see if this seem right
10 ohm – Just moving
22 ohm – Top of Reserve
75 ohm – 1/2 Tank
215 ohm – Full Tank (slightly above)
Shorting the Reserve light turns it on.
Does this seem right? I saw other talk indicating 10-90 ohms? I didn’t have a real sensitive pot but it at least took about 2 turns on my 1 k pot.
Jeff

— On Mon, 4/6/09, Hartmut Mees <hartmut@paspeedo.com> wrote:

From: Hartmut Mees <hartmut@paspeedo.com>
Subject: RE: Lipnichan Fuel Sender for Sonett III
To: “Jeff Lipnichan” <lipnichanj@yahoo.com>
Date: Monday, April 6, 2009, 7:39 PM

The way that we do it here is with an resistance substituter. We will power up the gauge and simulate the fuel sender operation. This way you can make note of the ohm values at FULL and EMPTY. The G is usually the GAUGE connection, and WK the warning contact. I usually turn the ignition on, and dial in the ohm value at the sender connection. Call me if you need any help with this.

Hartmut C. Mees
Palo Alto Speedometer, Inc.

718 Emerson Street
Palo Alto, California 94301-2410

tel : 650.323.0243
fax : 650.323.4632


From: Jeff Lipnichan [mailto:lipnichanj@yahoo.com]
Sent: Monday, April 06, 2009 4:56 AM
To: Hartmut Mees
Cc: Adam Lipnichan
Subject: Lipnichan Fuel Sender for Sonett III
Hello,
We recently sent our fuel sender in for repair. Adam has been trying to convey some of the requirements (this is our project car) and I thought I could help. My backgound is electrical so I can try to get some more specs to help calibrate the sender/gauge if you explain what I need to measure.
The gauge is part of a multi gauge in the car. Adam was going to scan and send a picture. Back at the tank, we have two wires and a ground. One wire must be for the low fuel indicator and the other for the sender. I don’t know which is which but I think the sender has a W and G and I can see from the electrical diagram which color went to which terminal.
Can I hook a variable reisistor between either of these wire to ground, or between these to simulate the sender for the gauge? If you tell me the approx resistance and wattage I can try it (I don’t want to burn out the gauge). I looked through both manuals I had and the resistance was not specified, just the sending unit part number which I think Adam already supplied.
I can call later if that is more helpful.
Thanks,
Jeff

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