New Gauge Lights Set Off Alarm

[Shorty]

1985 Yanmar 3GMF on a Pearson 34. large instrument panel. Not sail-drive. I have installed VDO Ocean Series water temp & oil pressure gauges. Changed out both senders with a single terminal, no alarm lug Teleflex #52320S009 at the water and a VDO #360-009 at the oil with an alarm lug and a gauge lug. Ran a ground wire back to the engine block because I did not want to cut into the wiring harness. Gauges work fine .
Connected the lights to an available terminal on the tach light switch and the same engine block ground. Turning on lights also turns on, albeit not at full volume, the alarm along with the lights. Removed lights neutral from the same engine block ground as the gauges and tapped into the tach light neutral. Still sets off alarm.

Huh?

[bill good]

the yanmar alarm cct for temp and pressure were on/off switches to the engine block. if you used the wires in the harness then this is where the problem might be. the test for the alarms was the same switch for the internal light in the tacho if my memory is working.

[Shorty]

it is the same switch however up is momentary test, middle is off & down is lights on

[hellosailor]

"Ran a ground wire back to the engine block because"
I don't know those senders or that engine, but I've never met a sender that required--or could use--a separate ground wire. Normally senders ground by their threads into the engine block, and you cannot use teflon tape or you break that ground.

Do the new senders have the same number and type of terminals that the old ones did? Does VDO say they are suitable for this application?

[Shorty]

ground/neutral wire is from gauges not senders & senders are not taped, direct thread contact
Thx - oh yes, the oil sender is VDO & the water is marked Teleflex but there were also package marking which seemed to indicate a connection between VDO & Teleflex, and the senders work fine, the problem is with the lights

[hellosailor]

"Connected the lights to an...Removed lights ... Still sets off alarm."

One of two things: Either the lights (the warning lights on the main panel, not the illumination lights on gauges, right?) are connected to the wrong place, or the senders are the wrong resistance. Usually these circuits are designed so that the resistance of the sender changes, and when it gets "too far" it also gets low enough to allow the lamp to light up. Without knowing the technical bits and the schematic, that's just a ballpark guess, but it WILL come down to one of two things:
Wrong senders, or wrong conection for the lamps. Do you have a schematic of the electrical system, and can you work with that to find out where the lamps originally connected to?
And again...Wait till Monday, ask the company if they're familiar with this boat, they may have the answers right at hand. (Like, whether the senders are an exact replacement. I've been sold wrong parts by Gen-You-Whine authorized dealers in the past, too.)

[Shorty]

I do have schematic.
Pretty sure I'm on the right switch terminal, guage lights go on when tach lights go on, when switch is moved down. Momentary up is the alarm test.
I forgot that I left the temp alarm sensor in place because the block has a suitable place for another sensor just above the thermostat. So, I have both sensors installed. Alarm wired as previous & gauge wired to gauge then neutral to block.
Wiring for lights is completely separate from gauge wiring.

[hellosailor]

Then there's only one thing left to do: Buy a new boat! <VBG>

For me, one of the nicest things about having a cell phone is being able to call for tech support while I'm ON A BOAT without having to pay radiotelephone rates to do so. (Oh yeah, like that was ever going to happen.<G>)

[Shorty]

Right you are, new boat, perhaps a Morris. Say, could I borrow your credit card? Just a few hours would do.
Thanks so much, I love it when folks chip in to help.

[Shorty]

The mechanic at my boatyard said this is a problem with Yanmars, they seem to backfeed through one of the sensors somehow. I will be wiring the gauge lights to the running lights breaker. He acknowledge mysterious nature of it because the lights are completely separate from the gauge sensor circuits, but he's run into it before.

[hellosailor]

Shorty, it sounds like he means there is a "ground loop" or voltage loop in the wiring. Which is probably why he is a mechanic not an electrician or electronics tech.

Backfeed through a sensor? Heck, they work out of the box, so they CAN work. Kludging it may fix it, but figuring out what's broke probably would fix it better.

Schematic, multimeter, not rocket science.

[Shorty]

Brian is a good all around boatyard mechanic, diesels and other systems, but I doubt he would claim "electrician" status.