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Replacing VDO instruments on Lehman 135's

J

Jim_Lanza

New member
We have twin Lehman 135s in our trawler, and the instruments read erratically. I've tested the oil pressure and temperature on the engines and the Flybridge and inside helm are very close to being accurate, however, they sometimes just stop reading. The instruments are original (30 years old) and I'd like to replace them, but I understand that they require sending units that 'match' the guages.

Has anyone else completed this modification? If so, I'd like to talk with you about it. VDO was less than helpful when I spoke with them.

Thanks,
Jim Lanza
40' Albin Trawler
Punta Gorda, FL
 
Hi Jim, It would be best to change gauges and senders at the same time. Check with American diesel, they may still have some original VDO's or equivalent. 804-435-3107
Charlie w.
 
Clean all connections and grounds good put dielectric grease on all the connections. With the ignition on you should have close to battery voltage at all the senders. Short the wire to ground and the guage should peg.
 
Thinking about it look at the wiring diagram are the guages powered by a pulse generator like on a car guage cluster? If the gauges are fed battery voltage then any standard analog guages will work. You have single station or dual station senders and the tach either runs off a tach driver or from the alternator pulse? Your wiring willtell you where you need to go.
 
Most of the time erratic gauges are electrical problems, like someone said check all connections. If you ever replace gauges make sure you buy the right parts. There are MANY different types. Different pressure and temperature reading range. The sender HAS to be the same range as the gauge and a lot of people don't know that. Senders also have different working resistance range (ohms). Some have ascending resistance and others have descending resistance. I've seen different mismatch, one had a oil pressure that was low when cold and high when hot. The sender was working in the wrong direction of resistance for the gauge. The specs are listed on VDO parts catalog for both sensors and gauges just make sure to match them.
 
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