Oil gauge issues

[CassidyNZ]

Originally Posted by a64pilot

You didn’t read I believe it was post 6.
It’s not a reverse polarity thing nor it is it a swapping wires thing.
What it is is that one standard reduces resistance with increasing pressure, the other standard increases resistance with increasing pressure.

Having the wrong standard sending unit will make the gauge work in reverse, apparently. I have never personally seen this though.

Finding what you have is simple with a multimeter, simply measure the resistance with the engine off and with it running.

However the next problem is finding a sending unit the first works in the correct direction and secondly has the correct resistance values.

Thanks, I got all that but mis-read this part in that linked thread: “Try connecting the usual sender wire to one terminal on the sender and leaving the earth wire off as it may earth through the sender body.” which is why I commented that my sender has just one wire.

As I said earlier, I can’t imagine that a Yanmar would have two standards and since my gauge is original as was (I believe) the original sender and a genuine Yanmar replacement as a second reference, I’d be surprised if the sender was wrong. Clearly there’s a mismatch somewhere. I’ve sent an enquiry to Yanmar’s Service helpline - let’s see what comes back.

[wingssail]

Originally Posted by a64pilot

Pick one you like, be sure it includes a sender, depending on your engine thread may be an issue, Yanmar I believe is BSP, almost all gauges are NPT, I tapped mine out with an NPT with grease on it catch any metal shavings, very little actual tapping is required, the threads are close, but will not quite work without tapping.
https://www.amazon.com/s?k=Electric+...f=nb_sb_noss_2

Y

Oh, this is scary!

[a64pilot]

Originally Posted by wingssail

Oh, this is scary!

Not at all, and I did so at the advice of a Yanmar service tech. The threads are so close your more straitening than cutting threads, some apparently have tried screwing NPT into BSP but according to the tech you can only get a few threads in and that’s not acceptable.
Oddly the threads on the water pump where I installed a water temp sending unit are NPT.

But if I were the OP, I would measure my sending unit to see if it increases or decreases resistance with increasing pressure and try to find one that does the opposite, or install a different pressure gauge beside of the panel, in the boat.

Eventually I’ll get around to an oil temp gauge under the right gauge to make things symmetrical

[Wotname]

Originally Posted by a64pilot

........
But if I were the OP, I would measure my sending unit to see if it increases or decreases resistance with increasing pressure and try to find one that does the opposite, or install a different pressure gauge beside of the panel, in the boat.
......

For an even simpler approach, the OP only needs to measure the resistance of the sender with the wire disconnected and the engine OFF.

If is low (say less than 20 ohms) then it is of the type that increases with increasing pressure.

If it a couple of hundred ohms, then it is of the type that decreases with increasing pressure.

All of the common resistance type senders operate between a few ohms and a few hundred ohms.

[Wotname]

Here is a chart of some of values used in car gauges.

http://www.howardinstruments.com.au/...20Brochure.pdf

[Kelkara]

Weren't some Morgans built by Catalina?
In which case this might be interesting ...
https://www.catalinadirect.com/shop-...anmar-diesels/

1) Unless they are intimately familiar with Yanmar engines installed on Catalinas, it is highly unlikely anyone will be aware of this custom part. Speak to any normal Yanmar parts source either at a boat yard or any of Yanmar's many distributors across the country and it is likely you will receive incorrect information due to the specialized nature of this information.

[Wotname]

And for European and American oil pressure senders from https://fariabeede.com/site_manuals/IS0085d.pdf

[wingssail]

Originally Posted by a64pilot

Not at all, and I did so at the advice of a Yanmar service tech. The threads are so close your more straitening than cutting threads, some apparently have tried screwing NPT into BSP but according to the tech you can only get a few threads in and that’s not acceptable.
Oddly the threads on the water pump where I installed a water temp sending unit are NPT.

But if I were the OP, I would measure my sending unit to see if it increases or decreases resistance with increasing pressure and try to find one that does the opposite, or install a different pressure gauge beside of the panel, in the boat.

Eventually I’ll get around to an oil temp gauge under the right gauge to make things symmetrical

So I guess tomorrow when I go to the shops looking for a low oil pressure switch and a mechanical gauge I'll take a sample and make sure the threads match perfectly. I don't want to change the threads on my engine and leave a hidden problem for the next guy.

[ScottRhodes13]

Are you sure the wires connected to the gauge are the right ones? I expect one should be +12v and the other runs to the sender unit where it runs through the variable resister to ground. What if the line that is supposed to be a constant +12v is not? For instance, someone could have connected it to the low voltage side of the temperature gauge.

[wingssail]

Originally Posted by ScottRhodes13

Are you sure the wires connected to the gauge are the right ones? I expect one should be +12v and the other runs to the sender unit where it runs through the variable resister to ground. What if the line that is supposed to be a constant +12v is not? For instance, someone could have connected it to the low voltage side of the temperature gauge.

Thanks ScottRhodes, I believe the wires are correct for the oil pressure gauge and the low oil pressure alarm/switch. I have traced the color coded wires end to end. I have replaced the power and ground wires also (with test leads). Both the gauge and the alarm have only three wires, power, ground, and signal, and I have traced or bypassed each of them.

[ScottRhodes13]

Ok, another idea. Are you sure the gauge is connected to the correct sender? It should be on the oil filter housing. The light connects somewhere on the side of the engine, I think. Sorry if my ideas seem a little flakey. We've run out of reasonable explanations.

[CassidyNZ]

Originally Posted by Wotname

Are you looking at the original operation manual or the service manual. I only have the service manual and it shows this as a C panel which is slightly different to the panel picture you posted - more mysteries .

The manual that I have for the motor I have shows a different panel to the one you show, although they are both identified as C-type panels.

Images below show the C-type panel from my manual alongside the actual panel I have on my boat. As you can see, they are essentially the same.

@ScottRhodes - I’m not sure you’re directing you posts at but if it’s me, response is:

We’re dealing with an oil pressure gauge here, not temperature. My engine has two oil pressure sensors. One triggers the buzzer, the other operates the gauge. Both have just one wire on the senders. The pressure gauge has two wires and as I said in my original post, I switched them and got an undesirable result from the gauge.

The senders for the two gauges are on opposite sides of the engine and cannot be confused. Besides, the temp gauge operates normally.

@ a64Pilot - the picture you show of your (?) instruments look OK but imagine how I would put such an oil pressure gauge into the panel shown below. I have no real estate alongside the panel like in your pic - I have just the panel. Doesn’t work the same.

@ Kelkara - my boat was built by Catalina but was not built with a Yanmar, it originally had a Volvo fitted.

[ScottRhodes13]

@CassidyNZ, I was replying to you.

You mentioned that the boat has been repowered. I'm working on the idea that whoever did the work may not have been familiar with Yanmar, and could have wired things wrong.

I have a 4jh2-hte, also late '90s, on my boat, but a third party instrument panel, so don't know much about your gauges. But it's interesting that you say that the oil pressure sender and the buzzer switch are on opposite sides of the engine. On my engine, and according to the manual, the sender for the buzzer is on the right side of the engine (viewed from the flywheel), back toward the flywheel. The sender for the oil pressure gauge is on the oil filter housing, also on the right side of the engine, but further from the flywheel. I can't imagine how a wrong placement of the sender could cause the symptoms you're seeing, but it's possible.

Also, when you replaced the sender are you sure you got the right part? I know you said it matched the previous part, but that could also have been wrong. The Yanmar parts manual lists these numbers: 144626-91560 which was replaced by 119773-91500 which was replaced by 119773-91501 (thanks Yanmar).

[CassidyNZ]

Originally Posted by ScottRhodes13

@CassidyNZ, I was replying to you.

You mentioned that the boat has been repowered. I'm working on the idea that whoever did the work may not have been familiar with Yanmar, and could have wired things wrong.

I have a 4jh2-hte, also late '90s, on my boat, but a third party instrument panel, so don't know much about your gauges. But it's interesting that you say that the oil pressure sender and the buzzer switch are on opposite sides of the engine. On my engine, and according to the manual, the sender for the buzzer is on the right side of the engine (viewed from the flywheel), back toward the flywheel. The sender for the oil pressure gauge is on the oil filter housing, also on the right side of the engine, but further from the flywheel. I can't imagine how a wrong placement of the sender could cause the symptoms you're seeing, but it's possible.

Also, when you replaced the sender are you sure you got the right part? I know you said it matched the previous part, but that could also have been wrong. The Yanmar parts manual lists these numbers: 144626-91560 which was replaced by 119773-91500 which was replaced by 119773-91501 (thanks Yanmar).

Sorry this got a bit confusing. For clarity what I said was:

- that the senders for the two gauges (oil and temperature) were on opposite sides of the engine and couldn’t be confused.

- both oil senders (gauge and buzzer) only have one wire each and couldn’t be confused.

- I had already tried to swap wires on the back of the oil pressure gauge with undesirable results.

Having done Yanmar re-powers myself, I know them to be a simple plug-n-play situation when factory-supplied parts are used and it is near impossible to get electrical connections wrong.

As far as “have I got the right part”, I’m assured by the Yanmar agent who supplied it that it is correct. Also, the oil pressure gauge reacts exactly the same with the old pressure gauge sender as it does with the new one. AFAIK the installation in my boat was brand new, factory supplied equipment.

@ Wotname and a64Pilot, thanks for guidance on testing the sender which I haven’t been able to do yet. My problem is that irrespective of what reading I get, how do I know what reading to expect? How do I know what reading the gauge is expecting to receive? I can’t find a spec on it anywhere in Yanmar’s on-line info.

Anyway, I have logged a request with Yanmar Service Dept for info, specifically to find out if there are two different sender concepts (US v Euro). Personally I doubt it but you never know. Will obviously post their reply here when I get one.

[Wotname]

Originally Posted by CassidyNZ

..........

@ Wotname and a64Pilot, thanks for guidance on testing the sender which I haven’t been able to do yet. My problem is that irrespective of what reading I get, how do I know what reading to expect? How do I know what reading the gauge is expecting to receive? I can’t find a spec on it anywhere in Yanmar’s on-line info.............

You raise a legitimate quandary and I don't think testing will point to a smoking gun.

It will however hopefully give some more information which could help clear some of the fog surrounding this problem. Every small bit of evidence might be useful at some time later in the investigative process.

After testing the sender in the rudimentary fashion listed upthread, you should at least be able to say if your sender is the the type which increases it's resistance with increasing pressure or the type that decreases it's resistance with increasing pressure.

Should you wish to delve deeper into the sender, then remove it and connect it to a air pressure regulator and record it's resistance across the range of 0 to 100psi. See if this roughly corresponds to any of the resistance values I linked upthread. Again, this wouldn't point to a smoking gun, it will simply be another data point.

If you are keen, you can do a similar test with the gauge by connecting various resistance values between the sender wire and the engine ground. Record what resistance values corresponded to the pressure markings on the gauge - say 0 bar though to 5 bar. There are a few simple ways to do this but probably the easiest (IMO) is to get a cheap 0 to 500 ohm linear potentiometer from a electronics supply / hobby shop. The gauge should track the pot and you can check the resistance at any pot setting with a DMM.

Now you have hard evidence of what the gauge wants to see and what the sender is sending. Presumably it will show that the two are incompatible which is what we suspect but this will give proof to that suspicion. Will it help fix the problem? I don't know but IMO it is better than having no proof.

If Yanmar is unhelpful, send them the data with a "Please Explain the Inconsistency" and ask "Why Is It So" and what is the solution.

Do you still have the receipt for the sender you purchased or any other evidence showing it's part number? Does this match the part number in the manual after taking account of the various part number changes over the years. Google tells me there have been several part number changes but they should be identical in operation. Google also tells me this part number is used on quite a lot of Yanmar industrial engines.

I have also found a part number for the gauge from a European company but of course I can't tell if that is the same as your gauge part number.

I am sure there is a rational answer to the problem but it is going to take a lot of sleuthing IMO. This appears to be a systems fault rather that a component failure.

Here is a tale that is somewhat similar in essence to your problem.

A decade or so ago, a guy came to us to ask us to fix an intermittent problem with his aircraft's radar. It used to just stop working every so often and then "fixed itself". He had already spent three years and $30,000 trying to get it fixed and was tearing his hair out. He could have bought a complete radar and have it installed for that money but it had been a death by a thousands cuts to date.

It took me three months of gathering tiny bits of evidence before understanding why it stopped working intermittently and it took one day to get access to the problem wire and ten seconds to fix it. From memory, our invoice was around $1,500 for the labour involved. He went away singing dancing in joy!

The fault had been in the aircraft wiring since it was manufactured and over the years the problem connector / wire finally deteriorated to the point where is failed occasionally as the aircraft pressurised and "fixed itself" every time when the aircraft landed (i.e. depressurised and vibrated).

How is this similar to your fault? Well, everyone else was looking for a smoking gun whereas the problem needed the gathering and analysis of apparently unconnected data (plus an understanding of how the system really worked at a component level).

IMO we are still in the discovery phase of your issue as the smoking guns were ruled out long ago.