Need a tach signal

[robinimpey]

Can anyone tell me where I can locate a tach signal? I have seen one another post that it is the blue wire coming off the alternator. Is that true? The reason I ask is that I have unplugged the blue wire and the tach still functions, which makes me think that's not where the tach gets a signal from. I'm certain that it must come from the alternator, just need to know where to tap in to get the signal.

Hooking up cruise control and if and when I get it working I'll give you an update.

Thanks for your help

[BadgeStar]

The tacho gets it's feed from the back of the injection pump! If you take a look you should find a wire on a spade type connector somewhere on the back of the pump.

Barry.

[Erebus]

Hi Robin,

I remember reading about the blue wire too, but I don't really see how the alternator can provide a tach signal. I can see it being able to answer the "is the engine running" question, but for the tach signal you want to know how fast the engine is turning over. And unless someone during design figured out the ratio of alternator revolutions versus engine revolutions that would be awkward.

Just my puzzled thoughts.

[bae146]

Hi Robin,

I remember reading about the blue wire too, but I don't really see how the alternator can provide a tach signal. I can see it being able to answer the "is the engine running" question, but for the tach signal you want to know how fast the engine is turning over. And unless someone during design figured out the ratio of alternator revolutions versus engine revolutions that would be awkward.

Just my puzzled thoughts.

A few diesels do get their tach signal from their alternator. Actually it is quite a easy thing to do, if you are electronically inclined. However as badge star says the pickup is off the injector pump.

[JMK]

I had a mechanic friend who area of expertise is vehicle electrics take a look and he said that my particular alternator did not have the required terminal to get the signal I needed for my remote start. I can't find anything in the pretty scetchy wiring diagrams I've found so far. I tested the blue wire anyway and it does not work for that purpose.

I wonder if there is just the one wire at the back of the injection pump. THat would be a convenient spot to get the signal. Does that wire have AC current in it?

Where did you get a cruise control setup, is it available as an aftermarket kit?

[robinimpey]

Hey Barry you're right, that was the spot. Not much room in there for big North American hands! Cruise control is now working and I'll post some pics later of how I set it up and the equipment I used.

Thanks for the speedy replies!

[JMK]

Guys,

Would this be the correct wire, the one on the left?

[robinimpey]

Yes it is the one on the left, the one with a black wire and a white wire. The black goes to ground on the engine block about 6" back from the plug in your picture and the white wire goes up and into the black plug with about 6 wires that is mounted above the injection pump. This is a much easier place to access your tach as there isn't much room down in there for making connections.

[JMK]

Thanks for that.

I went out with great hopes, only to be bummed out in the end.

I spliced into it but no luck. I tried to program the remote starter anyway, but it is not able to read a signal to know that the engine is running, so it starts the engine and then shuts it off after 8 seconds.

Supposedly I should be able to read at least 1.8 V AC from it. If I read it I get a momentary flash of 1.6 V - 1.7V then it zeros out. Raising the RPMs also does not raise the Voltage, so it seems like it's not the right one for me. Did you have to read the wire to see what it's output was when you connected your cruise control by any chance?

[Green1]

I'm currently arguing with my remote starter, I'm not sure where it's getting it's tach feed, but it's not quite right, sometimes it works, other times it can't tell the engine is running.

My next plan is to ignore the tach feed and take an alternator feed instead (my starter can use either with the flick of a switch) I figure that will probably be more reliable as with the tach it seems to care exactly what RPM you're at, whereas the alternator will be a simple "is it running" yes/no.

[JMK]

Thanks Green. Well when robinimpey posted his pic's I saw I was on the wrong wire. So I did it again, and lo and behold I got an AC signal that changed consistently with the RPM's, going from around 1.2 AC Volts at idle to around 2 V at around 2000 rpm. So I was full of great hope when I attached the Tach wire for the remote starter ECM to it even though the instructions say you need a minimum of 1.75 AC VOlts, which I needed almost 1500 rpm to reach - albeit a little high for a regular 'idle'.

However the ECM could not sense the vehicle was running even if I raised the RPM's to 1500. THe manual also says you need some minimum frequency, maybe that was the problem. It's left me wondering if there is something I can do to take the signal from that line and amplify it somehow, E.G. a transformer that doubles the AC current perhaps?

To make matters worse I see in the ProStart manual that they will only give telephone support to 'certified technicians'. I may call them anyway, and if they refuse to talk to me start a real nice web page up that will get ranked high in Google telling everyone that will listen not to buy their products - I got this on on sale at Canadian Tire for $150.00 which is about the same price for the Bulldog one I put in our LHS that you could get, and I did get, lots of tech support on the phone for.

BTW, check the other thread about the lights out, I see SuperBright does not have those surface mount festoon bubls but do have some other bulbs that may work better. I've also come to the conclusion that I could use brighter T10 bulbs in that signal light socket which seem to be easily available.

[Green1]

another option I've heard for remote starters that won't take an alternator feed is a device they call a "tach generator" it will take a feed from a constant source (like the alternator) and generate an AC signal that looks to the starter like a tach signal...