My Engine

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XUD Marine
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Re: My Engine

Unread post by XUD Marine »

Thanks, yes, testing them in hot water makes sense.
The port on the top is already used for expansion, dumping into the header tank.
If I were to add the sensor as a third one, I could probably drill and tap one of the blank holes on the side seen in the top view. But I think swapping one would be best, a gauge and a warning light should be sufficient.

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white exec
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Re: My Engine

Unread post by white exec »

That sounds good.

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Re: My Engine

Unread post by XUD Marine »

Now my thought are turned to the dashboard and instruments, I'm thinking again about a tachometer.
white exec wrote:
06 Jul 2019, 12:00
If you need an engine tacho (I would think you would), there are other ways an electronic one could be fed from the engine. One easy sensing point is the LH (flywheel) end of the camshaft, where the original HP pump pulley was fitted. As the camshaft runs at half crank speed, two triggering pips (at 180°) would be needed. I did this addition myself, years ago, when upgrading a N/A 1.9D to a full instrument pod, with tacho.
Well I have now covered up the cam shaft end. Though it may be possible to make a modified end cover with a sensor hole and provision for mounting.
But there was another idea.
sparksie wrote:
21 Jul 2019, 21:16
This is my day-to-day job and I wouldn't advise using the inductive pickup for the tacho.
Much more reliable and, therefore, more commonly used in the hostile marine environment, is the alternator driven tacho.
Many alternators have a "W" terminal as standard, but if yours hasn't, it's a simple thing to add one.
The tacho itself will cost the same as an inductive type, but the wiring is slightly simpler, needing only +,- and w connections.
If you buy a new tacho, it will come with instructions for calibrating it.
My alternator appears to have just two connections, 1, the charge and 2, wire to the battery light. There is that other thing that connects back into the unit again, I don't know what that is.
alt02.jpg
I did a search for how to drive a tachometer from an alternator and found this video:-



That's probably not the same kind of set up mentioned, but it seems fairly simple to do. Though I have not yet found these things outside of the US.
The "W" terminal solution sounds more robust, but I don't really know anything much about it.
If it helps, this is the alternator label.
If it helps, this is the alternator label.
Last edited by myglaren on 10 Sep 2019, 22:37, edited 1 time in total.
Reason: YouTube link

XUD Marine
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Re: My Engine

Unread post by XUD Marine »

Is this something like?
https://www.vwwatercooled.com.au/forums ... 31515.html
It's a different model, but I suppose the principle is the same.

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white exec
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Re: My Engine

Unread post by white exec »

If you can manage to create a W connection to the alternator, there are a good few diesel tachometers on Amazon UK, such as the Eling brand. Some have hours-elapsed display too.
This one looked pretty good - appropriate rev range, and ability to accept different inputs (including alt_W):
https://www.amazon.co.uk/Waterproof-Tac ... way&sr=8-1

Good choice of hand held non-contact tachometers/rev.counters (for calibration), from £10+.
You might find matching dash-mount temp, voltage, etc units as well.

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Re: My Engine

Unread post by XUD Marine »

I've been a bit quiet here, having not made a lot of progress over the last month. Been too busy with that "work" thing which has been encroaching on my weekends through September.
But I got back on it a little bit now.
I got the combi volt, temp and pressure gauges with senders. Tested the volt and temp ones and they appear to work. They are not fitted yet as I need thread adaptors making, so have not tested the pressure gauge yet.
The volts I did with an old battery in the shed, the temp I did with a mug of hot water from the kettle.
I took the two sensors out of the stat to test, but got no result. I think the hot water was not hot enough to trip the switches, maybe need to get a torch on them to get hot enough.
I also got a tacho dial, it says it will work off either a W output or a magnetic signal gadget.

I decided to have a go at adding a W output to my alternator, following the instructions in that VW link I posted above, how hard can it be?
Had a hell of a job getting the thing apart. One of the 4 long screws absolutely would not be moved, the other 3 were relatively easy.
Knackered the head trying, so that was going nowhere, but this one unlike the others proruded out the other side and had a nut on it for some reason (yes, I removed the nut). So I had to try moving it from that end.
Mole grips, no. A nut against another nut, just shredded the thread off the nut. Nut with thread-lock, no. Nut against a nut with thread-lock, no. Nut welded to the screw, I'm hopeles at welding and failed to do it.
Last resort, cut flush and drill it out, so the replacement will need the nut. But drilling a steel screw in an aluminium case is near impossible, without means to hold it exactly in place. This was Saturday, when nothing was going my way.
Then progress Sunday, last, last resort, take a hacksaw to the exposed mid section, that got it apart, still leaving the threadded end in the rear casing. That did eventually come out by putting the cut end from the middle in the vice and turning the casing round it. Probably eased by the failed drilling attempt taking away part of the casing next to the thread.
Anyway, after getting it apart, I soldered in the new wire to the end of a stator winding and threaded it through the W hole in the back where the terminal was not.
Got it back together, bar the one missing screw that got destroyed, but I found a replacement for that today.
The wire should be long enough to reach the junction box I will place at the engine front, so no need for any exposed connector.

Also made a start at putting a few wires on the gauges, at least the ones I have somewhere to go at this time.
gauges01.jpg
These are just power wires so far, linking common sources. Gauge power off the ignition, the lighting on a separate source, probably on a switch with the nav lights (off the Aux batt), a bit like how your car dash lights up when you put your headlights on. The Volt + is not connected as I will probably have a source switch between the engine battery and the aux batt. Sensor wires yet to be connected.
I did start scribbling the first draft of a wiring diagram too, to plan what will be included/needed and what goes where. Can then look at things like current draw, fuses, cable weight and suchlike.

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Re: My Engine

Unread post by XUD Marine »

I did some further testing on the temp sensors, the originals and the new one that came with the gauges.
When I tried before with a mug of hot water from the kettle, I didn't get a result with the original sensors, I don't think the water was hot enough, or held its temperature long enough.
This time I used a blow torch to get more heat, first testing with a multi-meter on continuity mode.
I was able to confirm the two sensors are as shown in the diagram on the previous page. The black one was a straight "make or break" on/off switch when it got hot, so for a warning light.
The red one could have been a second warning light or a thermistor. When heated (and cooled) it showed varying degrees of resistance, so I concluded it was a thermistor.

I also tested the new thermistor in the same way, though it had proven to work with the gauge in my previous test with hot water.
But I think I overcooked it this time and broke it. It initially showed no connection when cold, then when heated, made a connection, as the original did.
But then after cooling down it was still connecting.

My next test was to try again connected to the gauge, with power form an old battery, which had previously worked on the new one.
This time the gauge just shot straight up to the max, even when cold. So I think I must have maxed it out by overheating and its stuck now.

I tried the same with the old thermistor connected to the new gauge. It appeared to work, with the needle moving up and down as I put the flame to, and away from, the sensor.

So my question is: are these kind of thermistors and gauges generally compatible and calibrated the same?
I think it's safe to say that new thermistor is bin-fodder, but the old one seems to still work.
If I can use the old one that saves a job as it will fit straight back where it came from with no need for any thread adaptor as the new one would need.
The only question is whether it will be correctly calibrated with the gauge. I know it sends a signal that moved the needle, but will it give a true temp reading?

As for the alternator and tacho, the alternator is back on the engine where it belongs with its new W output wire coiled up ready.
I read the instructions on how to calibrate the tacho. It says for a W signal set the ratio to the number of poles in the alternator divided by 2.
So according to that, setting it to a ratio of 6 should be correct, though it maybe should be tested once the engine is running.

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white exec
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Re: My Engine

Unread post by white exec »

Have just read both your last two posts, so I missed the penultimate episode!

Temp gauges and their thermistors are matched pairs, so you can't use any old sensor. It may produce a reading, but unlikely to be the correct one, or correct over the range.
Don't like the idea of flame testing either thermal switches or thermistors. Asking for trouble, as discovered.
Testing of the temp gauge best done with a mug of boiling water, which will be 100C (at sea level.....which you should know all about! :roll:). An ice-water mix will give 0C, but probably no use here. Best to get/borrow a known good thermometer. If the gauge more-or-less agrees with the thermometer all the way up to 100C, probably ok to assume it's correct above that. 130C is max likely to be encountered without boiling, and 90-105C a reasonable day-to-day figure. The thermostat will fix the lower temp, when everything fully warmed up.

If you are ordering another thermistor for the gauge, might be worth getting two, one as a spare, particularly as these are aftermarket/accessory items, which could be difficult to replace at a future date.
You could also plot a graph of resistance against temperature; the sort of nerdy thing I'd probably do.

Don't allow +12v (or Gnd) etc to be applied to the sensor input of the temp gauge, as it might damage it. The input will have been designed always to be used with a series resistance (the sensor) attached.

I remember wrestling with long alternator bolts in the past. The steel bolts nicely corrode into the aluminium holes and threads.

All sounding good, not least getting the W connection done on the alternator.
Exciting! \:D/

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Re: My Engine

Unread post by XUD Marine »

Yes, hindsight is always good, the blowtorch was probably overkill. #-o
But kettle water wasn't up to it, by the time I get from the kitchen to the shed, then mess around with wires, it's cooled down. Accordign to the manual the warning switch goes at 103 to 107, the emergency one at 110 to 114, so the kettle won't do that.
Maybe should have put the water in a small pan and apply the flame to that. Then I can apply more or less heat to the water on site.

I had a look and it seems like you can buy just the sensor alone. Though I think I will test the old one with a thermometer (in water) to see if it's anything like right on the gauge, I may be lucky.
When I think about it, a lot of car temp gauges don't have units, just a blank scale and you know it's cooked when it gets to the red mark. But since this gauge does have units, I don't think I could live with it not being right.
The gauge ranges from 50 to 150, so it covers the normal running temp, and above. But it won't show anything from a cold start, I don't suppose that matters too much.

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mickthemaverick
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Re: My Engine

Unread post by mickthemaverick »

I have been following this thread and have nothing direct to add other than to give you a tip. When I have to test thermo devices above 100 I use a small saucepan with oil in it. You can heat that on the stove (best use cooking oil to keep stmbo happy :-D ) up to 160+ using a thermometer (I use a meat one) and then test accordingly. Good luck

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white exec
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Re: My Engine

Unread post by white exec »

Good tip on the oil. Hadn't thought of that.
Careful not to set it alight! :bomb:

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mickthemaverick
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Re: My Engine

Unread post by mickthemaverick »

As long as you work around the temperature range on your guage, 50-150, you should not have any burning issues. The flash point of most vegetable oils is well over 200C usually around 300-330C so at your temperatures it will be quite safe from igniting but don't spill it cos it will burn you at that temp.!! :wink:

XUD Marine
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Re: My Engine

Unread post by XUD Marine »

Thanks, good tip about using oil instead of water. Seems obvious once you hear it.
I just need to get hold of a thermometer, though I looked and they are quite inexpensive buy.

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Re: My Engine

Unread post by XUD Marine »

I got one of those digital thermometers and tried the original thermistor with the temp gauge.
The reading on the gauge was well below the thermometer reading.
I thought I would just use water in a pan to begin with.
With the thermometer reading 95 the gauge said 70, so no good.
After that I didn't think it worth getting messy with oil.
I ordered another temp sensor which appears to be like the one in the kit, hopfully it will work with the gauge.

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white exec
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Re: My Engine

Unread post by white exec »

If your dig thermometer is one of the non-contact (infra-red) ones, they are most accurate when pointed at a matt-black body, so worth placing something blackish on the liquid (eg a strip of metal) and pointing the spot at it. If thermometer is an immersion probe, shouldn't be a problem.

As discussed, thermistor must be gauge-matched, not a PSA original. Apologies if misunderstood.