Oil and Temp Gauges not functioning

[kaa2021]

Hi Y'all!
I'm hoping someone can give me a little clarity or advice here. We own a 1986 Alberg 37, with a 28hp 2003 Volvo penta diesel engine. Most of the gauges in our engine panel were functional during survey/sea trial in November. Then, they stopped functioning. I had a local marine guy take a look, and he said I needed some new sensors for oil and temp gauges. My alternator was also not charging my battery, and my tach not functioning. I waited two months for these sensors, finally, today, the new sensors are put on, and now I am being told that it is my gauges, that I need VDO gauges specifically and that my current ones are not compatible. I am a little perplexed as to why this is just an issue now, when all of this was working in November. Anyone else experiencing a similar issue? I am a little hesitant in buying new gauges, since 1. they appear to be newer and 2. I was not told that it was an issue when they first diagnosed my problem 2 months ago.

[Dsanduril]

It's been a while since I worked on that engine, but I would suspect an electrical issue. If you can start the engine normally then I would suspect the key switch (8) at position 15B as this provides power to all of the instruments (and I think the alternator, but I am not certain on this point). If you also can't start the engine normally then I would suspect the fuse block on the engine (6).

You can get the workshop manual online. Page 27 has the electrical schematic for the deluxe version with gauges. There should be a blue wire coming off the back of the key switch that should be at 12V when the key is in the run position. You could also have a look at the relay (5), one set of contacts carries the negative connection for all the instruments but not for the starter, so if the negative contacts are not working properly (or there's a bad connection to them) then the engine could start but not have working gauges. Also look at the D- connection on the back of the alternator and from there to "ground" as that is part of the negative circuit as well.

Here's a pretty poor photo of the fuse block (and the relay is just under it IIRC), it has caused me no end of problems over time. There are four fuses in the plastic block, only one is used, the others are spares, you move the wire from one connector to the next when you want to change the fuse.
Penta 2003 Fuse.jpg Views: 139 Size: 97.8 KB ID: 235592" style="margin: 2px" />

[GordMay]

See “Basic Engine Gauge Theory and Testing”
➥ https://www.cruisersforum.com/forums....html#post2597

[SouthBaySailor]

The gauges can be tested. It appears that it is a broken ground probably near the alternator. Install a ground wire from the alternator ground lug to the battey ground shunt on the house wire side. The gauges are typically 24 ohms. Ground one side and see if the needle pegs to the opposit side.

[Lake-Effect]

Originally Posted by kaa2021

Hi Y'all!
I'm hoping someone can give me a little clarity or advice here. We own a 1986 Alberg 37, with a 28hp 2003 Volvo penta diesel engine. Most of the gauges in our engine panel were functional during survey/sea trial in November. Then, they stopped functioning. I had a local marine guy take a look, and he said I needed some new sensors for oil and temp gauges. My alternator was also not charging my battery, and my tach not functioning. I waited two months for these sensors, finally, today, the new sensors are put on, and now I am being told that it is my gauges, that I need VDO gauges specifically and that my current ones are not compatible. I am a little perplexed as to why this is just an issue now, when all of this was working in November. Anyone else experiencing a similar issue? I am a little hesitant in buying new gauges, since 1. they appear to be newer and 2. I was not told that it was an issue when they first diagnosed my problem 2 months ago.

Here's a link to some instrument docs. It has lots of useful info that applies to instruments besides Faria, but the main reason I linked to it is that on page 35 it has a flowchart for testing engine instruments.

Also, based on your report of not charging and tach failure, your root problem might be a failure in the alternator (tach output or regulator). I would resolve those problems first, before chasing the oil & temp gauges or senders.

[Wotname]

kaa2021, I guess you already know this by now however let me say it aloud - you need a new local marine guy. The existing one gave you very bad advice.

As others have posted, get alternator charging and the tach sorted and most likely the gauges will work again using the old sensors.

Gauge troubleshooting is a reasonably simple skill and clearly one the local marine guy lacks.

[DougR]

Here’s a quick tutorial on how the gages work on your engine:
- 12v power comes from the starter motor terminal to a pin on the relay under the fuse block, and branches off that pin and goes to the fuse block mounted just above the relay. The power goes thru the fuse block and immediately to the wiring harness connector adjacent to the fuse. Thru the wiring harness connector into the harness and hence to the instrument panel, all on red wires. Once in the panel it goes to the key switch.
- When you turn the key to the “on” position power flows thru the switch and to both the oil pressure gage and temp gage on the blue/red wire. The b/r wire also powers up the tach and the alarm module and everything else on the panel.
- When the key is on power flows thru the gages and exits the gage on the light brown wire (for temp gage) and on the blue wire for oil pressure. The power flows backdown to the engine in the harness on the respective wire to the sender, goes thru the sender to ground, and this flow thru the gage and it’s sender causes the gage to display a reading.
- When the temp changes or the oil pressure goes up and down the resistance in the sender changes which allows more or less current to flow thru he gage, and the gage reading changes.

If you follow my description on the wiring schematic found in the linked manual you will see how it all comes together......

As already mentioned check for voltage along the path described, and also for good grounds on the engine.

[Cadence]

You have an issue with the ground.

[NorthCoastJoe]

Make two jumper wires with alligator clips.
One from battery + to the + terminal of gauge.
Second one battery - to the - terminal of the gauge.

Gauges should jump when hooked up to power.
I have a box full of used VDO cockpit gauges if you are interested, both metric and american scales.