Tach/Wiring

[Cloroxbottle]

Volvo 2003 Engine, tach is wired to an EMU1

https://www.actisense.com/wp-content...issue-1.06.pdf

through some convoluted back and forth, and is not displaying, Worked initially when we bought the boat, then intermittently, now not at all.

I’ve uploaded five pictures...the first is what I suspect to be an inductive sender for the tach.

The wiring harness appears to terminate in the back of whats shown in picture #2 so I’m assuming the attachments on the front are for some combination of engine data and could be connected to the EMU1?

I’m not entirely sure what #4, the darker blue box is or what it does.

I tried disconnecting the wires from the front of picture #1 stripping and crimping new ones, and connecting it directly to the plus and minus tach inputs of the emu which didn’t give me a reading.

Suggestions?

[DougR]

The sender/ switch in your first picture is a temperature switch which drives the high water temp alarm......mounted in the coolant in the cylinder head.

The 2003 engine drove the tachometer in one of two ways, depending on the vintage.

Originally the tach was driven by a two pole inductive pickup which was mounted on the front of the engine and counted teeth on the camshaft drive gear. It was connected to two gray wires which ran to the back of the tach, and was located right near the oil alarm switch and the oil filler cap.

Later engines drove the tach from the "W" terminal on the alternator and used just one gray or gray/black wire to the tach.

Hope this helps.

DougR

[redbeard1]

Hi,


I have a 2003 penta.


Your image #2 is a relay. I'm attaching a wiring diagram that shows how this relay connects to your wiring. On my engine, this relay does not directly connect to the tach or tach sensor. The wiring diagram applies to engines that drive the tach via the W terminal on the back of the alternator. I'm also not sure how your emu changes the wiring diagram, but page 14 of your pdf seems a good place to look.



I'm also attaching a picture of my alternator. At the time, I was debugging an issue with my tach, so my multi-meter clip is attached to the W terminal. Hopefully, it will give you an idea of where the W terminal is located (assuming your tach is driven this way).

[Cloroxbottle]

Thanks, appreciate the wiring diagram and esp the picture of the alternator. The temperature switch is just an on off switch, correct? It doesn’t transmit information that could be displayed on a gauge calibrated in degrees, just drive a buzzer and/or an idiot light?

[Cloroxbottle]

Ok, so after endless searching I found this diagram on the internet. It appears to match the back of my alternator. When I got back in there, the pictured rusted bit came off at the place labeled M4. Looks to me like at some point multiple wires were attached. The inner most, probably to the non functional tach on the instrument panel, the middle was perhaps the first wire leading to the emu or perhaps a replacement for the mechanical gauge tach, and th outermost was the most recent attempt to wire the emu...?

[redbeard1]

Originally Posted by Cloroxbottle

The temperature switch is just an on off switch, correct? It doesn’t transmit information that could be displayed on a gauge calibrated in degrees, just drive a buzzer and/or an idiot light?

Hi, there are two types of temperature switches. #1 in the wiring diagram I posted feeds a gauge. #3 in the diagram just triggers a buzzer and light.



I have #1 and am enclosing a picture of what #1 looks like.


I just read you found the problem. I had dug up a better picture of my alternator showing the W terminal. I'll post it in case anyone else looks at this thread.


edit: I think my temperature sensor is both some type of combined #1 and #3. My console has both a gauge and a light/buzzer.

[Cloroxbottle]

So I succesfully reconnected a wire from the alternator post to the EMU. Haven’t tested it yet. But during that install I noticed a green behind the alternator that isn’t attached to anything. It looks like it used to be connected to something because there is a loose connector lying under it on the floor of the engine compartment. Any idea what that might be for?

As far as the thermal switch I just have the light on the control panel and so I am guessing the sender is that as well.

[Cloroxbottle]

...however, when I look at the thermal sender, there are two prongs, and two wires that come off it instead of just the one prong and one wire that would be consistent with a sender that just drove an overheat alarm/light. Whats more, it appears as if two other wires have been spliced/soldered onto the original two by someone at some point, for some unknown reason.

[redbeard1]

Originally Posted by Cloroxbottle

Any idea what that might be for?

No idea. I would suggest following that green wire to see to what the other end connects. But I imagine you already thought of that.

[DougR]

Originally Posted by Cloroxbottle

...however, when I look at the thermal sender, there are two prongs, and two wires that come off it instead of just the one prong and one wire that would be consistent with a sender that just drove an overheat alarm/light. Whats more, it appears as if two other wires have been spliced/soldered onto the original two by someone at some point, for some unknown reason.

Late models of the engine were fitted with two pole electrical systems, that is instead of the engine block being used for ground, there were ground wires in the harness which grounded all the senders and other electrical functions. The only time the block was grounded was during starting, and that was accomplished with a grounding relay mounted beside the starter. The wiring diagram attached in this thread shows only the single pole system.

DougR