Oil/temp warning

[dclintonbaker]

I realized this topic has been posted previously, but I was looking for some guidance of how to move forward.

I have a 2004 C34 MK II with a universal M 35 BC engine.

Recently I had to replace the gearbox because of a worn drive plate. To do that the engine had to be taken off the mounts (which were replaced) and moved forward into the cabin. The wiring harness was reconnected and since then there has been a warning from the oil/temp buzzer. The mechanic replaced the buzzer and the oil pressure switch on the engine but the problem persists.  I'm suspecting that there is a short in the wiring harness. Moving forward I wonder if replacing the single wire from the oil sensor switch back to the panel would solve the problem or whether the whole harness needs to be removed and rebuilt. Any comments would be appreciated. 

[KWKloeber]

@d

Is it the OEM Westerbele harness?  i.e., does she have the stupid, convoluted, back-asswards Westerbeke wiring scheme on the B engines, or, like Ron's XPB, does she have the intelligent wiring scheme that Universal Oshkosh put on the pre-B engines?

-ken

[KWKloeber]

The mechanic replaced the buzzer and the oil pressure switch on the engine but the problem persists.

WOW.  Didn't solve the problem, huh?  Imagine that, Whack-a-Mole, willy-nilly, replacing parts instead of the mechanic troubleshooting the cause did nothing to resolve it. 
I trust that he isn't charging you for the parts and his ineptness as a mechanic?  If he is you got hosed.

Troubleshoot, troubleshoot, troubleshoot, THEN replace parts willy-nilly.  I'd love to start a forum JUSt addressing that, I will be repeating that 'ad infinitum"

FIRST, is it the oil switch or the temp switch that is alarming? (The first step he should have taken to troubleshoot it.) 
Rhetorical, but did he use the wiring schematic to understand why it is alarming?

the single wire from the oil sensor switch back to the panel would solve the problem or whether the whole harness needs to be removed and rebuilt.

B engines have no "single wire" from the oil pressure switch that drives the alarmm unless the wiring is NOT Westerbeke OEM.  The Wb scheme is a multi-conductor mess -- the alarm is always hot and shuts down when a "back voltage" is applied to the ground side of the alarm, driven by the fuel pump circuit. 
Please post a pic of your oil switch so we can take a look and provide a path forward.

I went thru the wiring on the forum and checking the voltages at different points with another owner.  If you can't locate that old post with a search I may be able to find it.

-ken

[Ron Hill]

dcl : Look for kens post or look for my Mainsheet tech note article on how I simplified the oil warning and the glow plug circuits.

A thought
 

[dclintonbaker]

Does have the original Westerbeke harness.
Here is picture of the new oil pressure switch. My mistake it has 2 connections.

[dclintonbaker]

I'm not sure if the image was attached to my last posting. I'm new to this board.

[KWKloeber]

I'm not sure if the image was attached to my last posting. I'm new to this board.

Nope, no pic.
You can always verify by signing onto the forum.  Attachments and embedded images are not included in the emails send out.

[Breakin Away]

You need to verify with 100% certainty that the mechanic installed the correct oil pressure sensor. Some models are fail-open, others are fail-close. I can't remember which is which, but this issue came up when I had to replace the oil sensor on my M35BC. Installing the wrong one would behave just like "a short in the wiring harness." For this particular item, I would look up the Westerbeke part number for your M35BC engine and get only a genuine Westerbeke part. That's what I did, although I had a very hard time finding someone who had it in stock.

Also, no offense to our Mk1 friends here, but for this particular topic I would be very careful about following any Tech notes for older boats unless you verify that they used the same type of oil pressure switch. Make sure that everyone understands the specifics of your vintage of engine.

Here's a discussion from my own personal experience, with lots of valuable suggestions from others: https://c34.org/bbs/index.php/topic,9214.0.html

[Ron Hill]

Breaking : What I did with my new engine (wiring for the M25xpB engine came with has the same screwed up wiring harness as the M35BC engine -- was to remove that factory wiring harness!!
 
What Westerbeke was trying to do is - when the oil pressure drops, the electric fuel pump stops and the engine then shuts down!! The only problem is that with the C34, the fuel tank is higher than the engine so when the electric fuel pump stops the fuel will continue to syphon and the engine will still continue to run!!

So what I did was to wire the glow plugs directly into the momentary (spring loaded) position on the key switch. Then I wired the electric fuel pump into the ON terminal of the key switch. The oil alarm switch is a single terminal and wired into a buzzer in the engine instrument panel. No pressure the alarm comes ON (very loud) and when the oil pressure come back up it is OFF (silent).  The Westerbeke wiring harness went into the junk pile!!

Simple as that !! 

A few thoughts

[dclintonbaker]

Interesting post from Breakin Away about importance of installing the correct switch.
Here's another attempt at a picture of the oil pressure switch..for what it's worth.

[dclintonbaker]

Ken's quote from 13 Nov 2016 at 02:51 :

To check the switch, remove the 2 wires to the switch, short the female terminals together (for a good connection I suggest a jumper wire w/ 2 male quick connect terminals, rather than taping terminals together.)  If your alarm problems go away, the switch has filed and replace it -- if not we'll dig deeper.

Should I do this?

[KWKloeber]

To check the switch, remove the 2 wires to the switch, short the female terminals together (for a good connection I suggest a jumper wire w/ 2 male quick connect terminals, rather than taping terminals together.)  If your alarm problems go away, the switch has filed FAILED and replace it -- if not we'll dig deeper.

Should I do this?

@d

That's not the OEM Wb wiring that I have seen when I replaced a "B" harness.  So from afar it might be difficult to tell what you have there or if the PO modified it.
Wb typically installs harnesses before painting the engine so all the wiring is Ice Blue color.  Even if not, the OEM wiring had one terminal crimped with two wires (one being red/white stripe) and the other terminal had one wire.  And those are not Wb terminals or Wb crimps.

I went thru the wiring on the forum and checking the voltages at different points with another owner.  If you can't locate that old post with a search I may be able to find it.

Did you look for that?

is it the oil switch or the temp switch that is alarming?

did he {mechanc] use the wiring schematic to understand why it is alarming?

I missed it if you previously answered this.

Disconnect the two wires.
See what the alarm does.
Verify whether the oil switch is open or closed (w/ engine off and running) using your ohm or continuity setting on your multimeter.

Report back!

-Ken

[dclintonbaker]

disconnect the two wires from the oil pressure switch..the alarm continues.
disconnect the temperature switch and the sender from the thermostat housing..alarm continues.
Testing the new oil pressure switch..engine stopped, open circuit  from both tabs to engine ground.
    "                    "          engine running, open circuit from both tabs to ground.

New information..now I have no tachometer reading, no fuel gauge reading and the temperature gauge reads ~ 200 F after engine running for 1 minute.

[KWKloeber]

Testing the new oil pressure switch..engine stopped, open circuit  from both tabs to engine ground.
    "                    "          engine running, open circuit from both tabs to ground.

The switch is between the two terminals.
Not the terminals to ground. 
Recheck the switch.

no tachometer reading, no fuel gauge reading and the temperature gauge reads ~ 200 F after engine running for 1 minute.

I presume with the items still disconnected as you described below?

[dclintonbaker]

thanks for your continuing interest Ken.
Oil switch is an open circuit with the engine off and closed circuit with the engine running.

My current project is the reconnect all of the leads from the engine to the harness that runs aft to the instrument panel.