How do I remove the oil pressure switch?

[TortolaTim]

Tom, my alarm had been inop since I bought the boat 2.5 years ago. The switch wasn't leaking, it was just the next logical step in my troubleshooting. Well, the alarm worked a few days ago when I installed the new switch. Yesterday I went out sailing...and voila! No alarm! The warning lights continued to work, but that's it. I went back today, took the panel out and did some voltage testing, everything is fine. I tried to short the switch and it wouldn't work. 20 minutes later when I started the engine....it worked again! I came home today and ordered a new alarm. I checked literally everything else, so I'm out of ideas. I'm not sure how the thing could work one day and not work the next!

[KWKloeber]

Tim

I presume that you have the single terminal switch.  If you shorted the switch terminal (or removed the wire terminal and shorted the wire) to ground, then you bypassed the switch.  If no alarm, then it's not the switch causing the no-alarm -- because you bypassed it.

Could be a bad (blue) switch wire itself; a bad connection @ the alarm; a bad 12v+ to the alarm; bad engine ground; etc.  Once the blue wire (or alarm S terminal) is grounded the switch is taken out of the equation.

[tvorgitch]

Tim,

I spent a good couple of hours testing the alarm light before I figured out the switch was disconnected.

It's very easy to test by getting 12V to the + terminal and then grounding the P (Pulse) or S (Steady?) terminal.

[TortolaTim]

Ken, before I replaced the switch (single terminal) I bypassed it by grounding the alarm itself to my panel ground. It went off. I also cleaned all the terminals and checked voltage at the panel. Ops check good. Checked continuity from the ring terminal that screws into the switch to the wire at the panel. Checked good as well. After replacing the oil press switch, alarm worked. Went out the next day and it didn't work. Ran the engine today for a few minutes, when I shut it off, the alarm worked again. The ONLY other thing I can come up with is that the voltage to the alarm tested at 11.5-11.6V. Is that enough of a drop to make the alarm only work intermittently? Voltage at the key switch itself was 12. I ordered a new alarm. I'm going to install it, AND wire the alarm pos directly to the key switch. Right now it is daisy chained to one of the gauges.

[KWKloeber]

Tim

What's your at rest btty voltage?  11.5 at the alarm is nuts.  It should be the same as delivered to the panel.
Thoroughly clean all the terminals.  There should be no problem picking up power for the alarm from a gauge (provided they are clean.) 

Test the V at several locations -- there must be a high resistance at one gauge terminal or there's a bad terminal crimp on the daisy chain.  Do the wire pull-out test (tug on each) to make sure there's good crimps on all of them.  If this is the OEM panel wiring the old automobile Stak-On terminals are crap and can be loose or corroded.  I had a wire fall out of one on the 12v distribution panel (re-crimped them all.)

I don't know specifically what alarm is in there and its minimum V, but I would guess that it would be under 12v.  When you had 11.5v there, did it sound by grounding the terminal?

If the non-alarm is intermittent then its possible that the S wire continuity is intermittent.

   

[TortolaTim]

Ken, I'll check the batt V when I get back, but I'm sure it's good. It is fairly new and I keep it charged up through an ACR. The start panel wiring, however, is the original with the old automotive type crimps and terminals. I am planning on re-wiring it all in time, but maybe I'll see it there's some bad ones and replace them now. Thanks again. I'll report back.

[KWKloeber]

Tim

I am making an ass/u/mption here that the batty voltage is not during charging for say 10-12 hours and no loads applied to it.  With only the key on (gauges being only current draw), you are basically looking at resting voltage (not under-load voltage.)  The panel voltage therefore should be near 13v with fully charged wet cells -- there should be near zero loss because there's virtually no current flowing.  So if whatever you read at the btty bank isn't the same at the panel, something is amiss.  Corrosion (especially on the negative cables) can be the cause as well as poor crimps.  Regardless if the battery isn't at resting voltage (has retained a surface charge) whatever is at the bank should be the same at the panel (unless there is a draw down -- something drawing current that shouldn't be "on.")

[TortolaTim]

<<Follow Up>>
I cleaned up, re-crimped, and replaced some of the wires at the engine panel. I wired the alarm "+" directly to the "+" wire coming up from the battery to the panel. Still no alarm. I replaced the alarm. It works now, and is loud enough to wake up the whole marina! I'm glad I dug into this project, as I'm now MUCH more familiar with the workings behind the panel, and will eventually re-wire the entire thing. While I was in there, I did properly re-crimp the wires to and from the start switch, they were looking pretty rough. Thanks for all the help!

[KWKloeber]

Tim

GREAT that you fixed the issue.  Your post is so apropos while we're talking about troubleshooting the engine power situation. 

Diagnosing is so much more rewarding than willy-nilly replacing parts (like a new, perfectly good oil switch)?  LOL
Diagnose, diagnose, diagnose, then replace.

I do have a few comments (education, not criticism.)

The lead to the alarm belongs on the key switch "I" terminal not the "B" (battery) terminal (or of course can be on the V+ feed to any gauge.)

You hit it right that it was a bad alarm.  But before replacing it I would have done one more step to verify it was bad.  Putting a 12v bulb in place of the alarm (could use a 12v tester or even use the light on one of your gauges) would show that the circuit was good and the alarm was bad (the only change being you substituted the alarm.) 
Engine off/no oil pressure = the bulb lights.
Engine starts/oil pressure = the bulb goes out.

When it comes the time to rewire the panel, ask questions!

- Ken

[Ron Hill]

 A friend of mine with a Bristol 45 had an old style fire alarm klaxon attached to the oil pressure switch - talk about waking the dead!!   Wow, it really got you attention when he started his engine!!!

A thought

[TortolaTim]

Ken, great points, thanks! I should clarify where I wired the alarm "+". I didn't take it all the way to the key switch. My gauges are all "daisy chained" together with the old original automotive style crimp terminals. The alarm was connected to the end of the daisy chain. I jumped it to the beginning, so the current is flowing directly through new properly crimped heat shrink marine wire to the alarm. A lot of the distribution at the panel uses these AutoZone double spade connectors. (They are everywhere behind the main DC panel too) I'm guessing that eliminating these guys is a priority in cleaning up the wiring?

[KWKloeber]

Tim

Ok, then you powered from after the key switch, not connected to the "+ wire coming up from the battery to the panel."  OR were you referring to that while troubleshooting??

Those piggyback adapters are "ok" but you know that I don't use any more connections than absolutely necessary.  In my mind those are bush league -- for 1970s, teenager under-the-dash tapedeck installs. 

On my boat it seemed that those male/female piggybacks must have asexually reproduced and have taken over EVERYWHERE.   I took out some and plan to get rid of them all. 

Quick disconnect terminals don't belong on a boat if there is any alternative.   Some old gauges on panels I've done had them but all the new gauges I use have #8 post terminals (although the lights are still all quick disconnects.)

But the type of terminal is actually irrelevant.  Obviously, one can daisy chain on post terminals using 2 (or 3)
ring terminals on a post. 
And with posts OR quick connects you can daisy chain by crimping multiple wires into a ring terminal (or into one quick-disconnect terminal.)

Say that on a panel one uses 16-ga for gauges/lights.  16-ga uses a Blue terminal (nominally good for 2,600 to 4,100 circular mils - CM.) 
(3) 16-ga conductors = 7,800 CM, so you use a yellow terminal (good for 6,500 CM to 10,500 CM.)
Sometimes you can fit (2) 16-ga into a Blue.  You can play with the wire gauge, terminal size, # crimped together, and how you layout the daisy chain to make it work w/o the piggyback adapters.

So, why Seaward used them is beyond me.  They don't save time (need to make more crimps compared to above) and they add cost.

OF COURSE -- this is just for low amp gauges and lights on a panel, I'd not use that method for any higher amperage terminals.

[TortolaTim]

Ken, Great info, thanks! Yes, my plan is to do as you said, eliminate the "bush league" spade connectors, and yep, they are EVERYWHERE. BTW, the alarm "+" is connected after the key switch, not to the run from the battery.
Cheers!

[KWKloeber]

Hey Tim,
I meant to mention that harbor freight has a few different test leads with alligator clips. I find them really handy to keep aboard just to be able to troubleshoot a gauge, lights - anything low amperage.
Or just to be able to clip my multimeter leads to something so my hands are free to fiddle while I'm checking voltage or continuity.