Teleflex 73742 trim gauge vs sender resistance values

komodo_goods

Seaman Apprentice
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Dec 31, 2023
Messages
34
Good evening,
I recently replaced my starboard trim sending unit with a sierra unit and cannot get the gauge dialed in. Symptoms are that gauge is pegged up with key off engine off and key on, engine off. This seems normal for this gauge as I verified other internet pictures show the same.

When turning the sending unit (it was indexed correctly) the gauge will peg to full down with no in-between sweeping.

I have bench tested the gauge in following configurations with 12vdc applied to I - G
1. Jumper from S - G = full down on gauge
2. 450 ohm resistor between S - G = 1/2 on gauge
3. 910 ohm resistor between S - G = almost full up on gauge.

The sending unit only has between 0-50 ohms within its full range of motion.

So my question is what is the incorrect or defective part? Is the sending unit supposed to be 0-1k resistance or has the gauge faulted internally and should function fully on a 0-50 ohm sender?

This is on a 1998 chapparral sunesta with an alpha 1 gen 2 outdrve.

Any assistance would be appreciated. I was only able to find one other post that referenced the sending unit as having 0 -150 ohms and nothing on the gauge.
 

alldodge

Moderator
Staff member
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Mar 8, 2009
Messages
41,542
The North American standard is 240 to 33 ohms (Empty to Full)
The European standard is 0 to 180 ohms (Empty to Full)
So your gauge is working closer to the European style

The 0-50 for the sending unit has me wondering if it isn't a switch
 

komodo_goods

Seaman Apprentice
Joined
Dec 31, 2023
Messages
34
The North American standard is 240 to 33 ohms (Empty to Full)
The European standard is 0 to 180 ohms (Empty to Full)
So your gauge is working closer to the European style

The 0-50 for the sending unit has me wondering if it isn't a switch
Well I called Sierra tech support and they were unable to tell me the resistance values of the switch but did agree to refund me. Only other thing I know to do is get a replacement gauge but teleflex no longer makes my model. Any other suggestions?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
41,542
Most likely will not find one that looks exactly like your old one.
Look into Faria, VDO, Autometer gauges, might get close
 
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