Warning Lights and Gauges

[weephee]

I have a Yanmar 3GM30F with the usual 3 warning lamps I would like to add a temperature and oil pressure gauge and also keep the warning lamps. Any idea how I would do that. I assume the sending unit for a warning lamp is different than the sending unit for a gauge so do I plumb them in with a T of some sort or how do I do it. Thanks

[DougR]

Usually the "sender" for high temp and low oil pressure alarms are really just switches that make contact if the oil pressure falls below a set level, or the water temp goes above a set temp. This making contact or closing causes the alarm to sound and the light to come on.

Actual senders, as used to drive gauges are variable resistances that change value as the oil pressure changes or the temp varies. This varying resistance allows more or less current to flow thru the sender, which means more or less current flows thru the gauge, causing the needle to go up or down. Because of this relationship between the sender and the gauge, it's necessary to have gauges and senders that are made to operate with each other, so it's necessary to purchase senders and gauges that are matched to each other's values.

Usually oil switches and senders are made with 1/8" pipe threads (or equivalent metric sizes) so it's not terribly difficult to "T" them together or find threaded plugs in the oil gallery to add a sender to drive a gauge. Some manufacturers also make combination units which contain both an alarm switch as well as a sender for a gauge, so that simplifies installations.

Temp switches are typically 1/2" pipe thread or perhaps 18mm thread, so it's more difficult to "T" them together. More often there are extra threaded openings in the engine block or head to accomidate a second sender.

I'm not super familiar with what's available on the 3GM30F engine for extra senders, so I would suggest going online and finding an installation drawing of the engine. Usually this will show the location of any extra ports for optional gauges. Failing that a dealer should easily be able to point you in the right direction.

DougR

[Dennis.G]

Note that there are combo oil pressure sender/switch units, so that at least for oil pressure gauge and oil pressure light/alarm can be accomplished with a single sender unit. I know at least VDO has this option as I installed one.

[Paul L]

Here's an older thread on the subject
http://www.cruisersforum.com/forums/...its-37032.html

[weephee]

Thanks everyone. Very useful information for me to proceed. I appreciate it