QuestionQUESTION: I have a 1999 Accent (no factory tach) and I'd like to install one but the directions that came with it weren't good. I do know I need to run one wire to the constant power source, one to the dimmer, one to ground, and the other to whatever reads RPM. I'm sure with some searching I can find the first two, the third is easy, but the fourth...I'm stumped. Where do I hook this up? The crank position sensor (and where's that? Is it easy to get to and attach a wire?), part of the electronic distributing system, somewhere else? Thanks!
ANSWER: First, I'm going to recommend you register for a free account at www.hmaservice.com (requires Internet Explorer). This will allow you to see the schematics for the vehicle (in the ETM section).
For your power, I'd think you'd want switched power instead of constant power. This will prevent the tach from being on even when the ignition is off. Since your car doesn't have a tach, I'm not sure if the tach signal wire is present at the cluster, but if it is, that's a good place to start. The tach signal is provided as an ECM output for the TCM and the factory tach.
If the wire is present in the harness connector for the cluster, there should be a white wire at pin #8 of connector I08-1. (Being able to see the schematic will be of great assistance to you in understanding the location. At the bottom of the schematic is a "component location" link. Clicking on "instrument cluster" should take you to a drawing of which connector is where). You should be able to use this wire for your tach signal. If the wire isn't present, you'll need to locate connector MC01 and tap into the tan or white wire at pin 13. To find this connector, click on the "in-line connector location" link at the bottom of the schematic. It will show a drawing of the location of the connector.
For the power, you can use a feed from fuse #10, or take the feed from the blue/black wire in connector I08-1 or I07-2 at the back of the cluster. This is the main power for the gauges, so it should be able to handle a tachometer being added. It's switched off the ignition, so the tach won't be on while the key is off.
As for the dimmer, you may not be able to do this properly. You can try hooking to either the green/white or green/black wire at the dimmer switch, but because of the way the dimmer is wired, you may not be able to do this properly. If not, you can try wiring into the output of the tail lamp relay to have the tach fully illuminated whenever the tail lamps are on.
Also, while at the cluster, you can take
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QUESTION: The bottom of your reply was cut off but I got the main point. I think instead of constant power it was the switched power recommended, thanks. Since there's no factory tach I don't think I'll have anything in the cluster for it ao where do I find the ECM? And how would I connect to fuse #10 in the box (under the hood or inside the car?)? If I'm still not sure I might take it to a mechanic and find out what the cost would be to have it set up but I doubt that would be cheap so I'd prefer to try it myself. By the way, it's a 2 5/8" gauge I'll mount on the dash if that matters. I probably wouldn't need the dimmer hooked up so if I leave the wire capped would that work or should I attach it to a light source? Thanks!
ANSWER: Sorry about the confusion, the last noncompleted sentence was to have been deleted. There were no further instructions.
The ECM is behind the left side of the dash, but you don't want to wire into that connector. The terminals are small and difficult to access. You want to access the wire at connector MC01 or at the cluster, if it's there.
Fuse #10 is in the inside fuse box. It'll be labeled something like cluster or gauge. (Sorry, I don't have a picture of the labelling or a car available to check).
If you don't need to illuminate the tach, you can leave the dimmer wire off. I'm figuring that you'll need to illuminate it at nighttime, though. That's why I suggested the tail lamp circuit if the dimmer didn't work.
In all seriousness, check out the website if you haven't already. The diagrams and pictures will be a much better help than I can ever be with text. Once you've logged in, click "Service Information," enter your year and model, and click on the ETM tab. You can then select the appropriate schematic (ignition system for the tach circuit, and illuminations for the dimmer circuit).
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QUESTION: Sorry for the delay (I was on vacation) and thanks for all the help. I got onto hmaservice and it did help quite a bit as well, however, I decided to let a mechanic tackle the installation so I wouldn't do anything wrong and since I have little free time. Everything was done and the mechanic said that the signal wasn't being translated by the tach, and that the gauge is probably looking for voltage while the signal generated by the car is in radio frequency. Does that sound right and is there any way to make the existing gauge work with the car? I told him to try pin 47 on the ECM or MC08 (I believe that's the one you said and agrees with hmaservice but I don't have the number in front of me; I gave the correct number though) so he should've tried both of those. When looking at other tach gauges I see nothing about what signal it picks up and many gauges are universal, literally "for every car" so is there any other connection that may send a voltage signal instead of the rf apparently going on here? Thanks again!
AnswerUnfortunately, the schematic doesn't indicate what type of signal is used in the communication line from the ECM. It's possible that it's a varying voltage signal.
If you need a pulse signal, you could try tapping into one of the coil signal wires (blue or brown wire at coil). You could also tap into the same wire at pin 25 or 52 of the ECM connector.
