[C320-list] Perkins 30 temperature gauge malfunctioning

[islgirl3 at aol.com]

Excellent write up.

Rich Nuzzolo 
On Thursday, December 31, 2020 mseyler <C320-List at Catalina320.com> wrote:
Clay,

If you have a volt meter you can measure the voltage on the back of the gauge.  (Measure with the key on, and the engine cold.)  According to the wiring diagram, There should be 3 wires connected to the back of the gauge.  One of the connections on the gauge should be labeled "+"; another should be labeled "-", and the third should be labeled "G".  (According to the wiring diagram the wire to + connection should be white, the wire to the - connection should be black, and the wire to the G connection should be green and blue, but you can't always count on that.)  You should find 12+ volts between the + connection and the - connection.  If you don't have 12 volts between the + side of the gauge and the - side of the gauge, you need to find out why not.  Sometimes it's a bad ground wire to the gauges, or just bad connection on any of the wires from corrosion.  Try cleaning all the connections and see if that solves your problem.

If you have 12 volts between the + connection of the gauge and the - connection of the gauge, measure the voltage between the + connection and the G connection.  It will likely be either be 12volts or zero volts.  If there is no voltage between + and G on the back of the gauge (and the gauge still reads nothing), try connecting the G terminal to ground, and see if the gauge goes up then.  If there was no voltage between + and G, but the gauge goes up when you connect G to ground, it's likely either the wire to the sender or the sender itself.

If the gauge goes up when you ground the G connection, try connecting the wire at the temperature sensor (just above the water pump on the Perkins) directly to ground (any bare metal on the engine block, or the B- terminal on the alternator), and see if the gauge goes up then.  If it goes up when you ground it at "G" but not when you ground the wire at the sensor, your problem is somewhere in that wire.  If it goes up when you ground the wire at the sensor, but not when the engine gets hot, it's likely the sensor.

Hope this helps.

Mark Seyler
S/V Reality, 
Catalina 320, #232
New Orleans, LA



-----Original Message-----
From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of Clay Carter
Sent: Wednesday, December 30, 2020 7:25 PM
To: C320-List at catalina320.com
Subject: [C320-list] Perkins 30 temperature gauge malfunctioning

My 1995 Perkins 30 has recently had some temperature gauge issues.  First I found the wire had broken loose from the sending unit—fixed that and the gauge was working again.  Not it has failed yet again—I checked the wiring and it is good this time.  I noticed the temperature gauge moving up, then it suddenly dropped to zero. Would you be suspicious of the sending unit, gauge or other?  How do you test a temperature gauge?

Thanks for any input.

Clay Carter
We’ll Sea #225
Alamitos Bay, CA