gauge help

[Geonovast]

I stand corrected... but why, oh why, would they make a police package without full gauges?

[Eagle]

So what's the easiest way to recalibrate a 6-cyl donor tach to read correctly in a 4-cyl? I'm not looking forward to pulling the cluster just to calibrate the tach, so if it's difficult, I'll just leave it. Wish I would've known that beforehand, 'cuz I'm sure it would've been easier to do before I put the 6-cyl donor cluster in. Guess these plug and play gauge clusters aren't smart enough to recalibrate themselves!

There is a potentiometer on the back of the cluster, next to the tachometer. It's a small, round thingie (technical term) with a plus-shaped recess in it for a Phillips screwdriver. I don't remember which way you have to turn it to go from 4 to 6 cylinders or 6 to 4.

[Eagle]

Just for the record replacing both sensors on front and back of the block for the engine temp. is best. You will get a more accurate reading.

Just for the record, the temperature sensor on the lower front of the block is for providing data to the ECU and has nothing to do with what reading you get on the gauge. The sender for the gauge is the one of the left rear corner of the head.

[Eagle]

I stand corrected... but why, oh why, would they make a police package without full gauges?

It has full gauges. The police packages don't have a tachometer because they don't need one. They were all automatics, and police have other things to worry about than how many RPMs the engine is turning.

[socal1200r]

So what's the easiest way to recalibrate a 6-cyl donor tach to read correctly in a 4-cyl? I'm not looking forward to pulling the cluster just to calibrate the tach, so if it's difficult, I'll just leave it. Wish I would've known that beforehand, 'cuz I'm sure it would've been easier to do before I put the 6-cyl donor cluster in. Guess these plug and play gauge clusters aren't smart enough to recalibrate themselves!

There is a potentiometer on the back of the cluster, next to the tachometer. It's a small, round thingie (technical term) with a plus-shaped recess in it for a Phillips screwdriver. I don't remember which way you have to turn it to go from 4 to 6 cylinders or 6 to 4.

 

Hmmm...maybe someone else will chime in on this one...what about switching it to the other setting from where it is now? Because if the donor vehicle was a 6-cyl, and it's now on my 4-cyl, I should just have to switch it to the other setting, right? I'm not going to remove the cluster until I know exactly what I have to do to get the tach adjusted from the 6-cyl donor vehicle to my 4-cyl, and pics would be VERY helpful! I'm not looking forward to wrestling with that speedo cable...

[Eagle]

Hmmm...maybe someone else will chime in on this one...what about switching it to the other setting from where it is now? Because if the donor vehicle was a 6-cyl, and it's now on my 4-cyl, I should just have to switch it to the other setting, right? I'm not going to remove the cluster until I know exactly what I have to do to get the tach adjusted from the 6-cyl donor vehicle to my 4-cyl, and pics would be VERY helpful! I'm not looking forward to wrestling with that speedo cable...

A potentiometer isn't a switch. It's a mini-rheostat. Turning it changes the resistance through a range. To calibrate it for a different cylinder count, you have to to have the cluster connected to the wiring harness and also have an idle tachometer attached to the engine (or use an optical sensing tachometer) to tell you the correct reading. Then you turn the potentiometer (or "pot," for short) until it agrees with the reference tach reading.

[socal1200r]

That makes sense, but I don't have another tachometer to use in order to calibrate it. So I guess it's going to read wrong for now...

[HOrnbrod]

It has full gauges. The police packages don't have a tachometer because they don't need one. They were all automatics, and police have other things to worry about than how many RPMs the engine is turning.

 

The police speedo fits right into an HO full gauge cluster and works very accurately - just has different colors. I had one in for awhile but didn't like the clashing color schemes. :D

 

 

A better option is fitting in the Euro cluster.

 

[socal1200r]

A potentiometer isn't a switch. It's a mini-rheostat. Turning it changes the resistance through a range. To calibrate it for a different cylinder count, you have to to have the cluster connected to the wiring harness and also have an idle tachometer attached to the engine (or use an optical sensing tachometer) to tell you the correct reading. Then you turn the potentiometer (or "pot," for short) until it agrees with the reference tach reading.

 

Eagle - just remembered I removed a tach from the bottom of the dash, the PO didn't wire it up (along with one of those 3-gauge clusters). Anyway, I guess I have a tach that I can use to calibrate the one in the cluster, but need help with the wires. It has 4 wires, red / green / black / white. I'm assuming one is to light up the tach (white?), and ground (black?), but where do the other two go (red, green)? I know I don't need the light wire connected to do this calibration, but if I can hook up this other tach, I'll compare it to what's on the tach in the gauge cluster, and calibrate it as needed. If you can tell me where these wires are supposed to connect to, I'll give it a try.

 

Thanks

[Eagle]

White is positive 12v to the light bulb.

 

Black is ground.

 

Red is positive 12v to the tach

 

Green goes to the negative terminal of the ignition coil. (Or to the tach output in the yellow diagnostic connector under the hood.)

[socal1200r]

White is positive 12v to the light bulb. Black is ground. Red is positive 12v to the tach. Green goes to the negative terminal of the ignition coil. (Or to the tach output in the yellow diagnostic connector under the hood.)

 

Eagle

 

Just tried to make this other tach work, no joy. I had alligator clip wires going to the ground and the green wire, and I pressed the red wire to the + battery terminal, and left the white wire unconnected. The needle moved ever so slightly, like it was getting power, but that was it. My problem is connecting the green wire. I followed the coil wire from the distributor, and it went underneath this black plastic cover thing on the passenger side inside fenderwell. I removed the black plastic cover, and the coil wire ended at this square block looking thing, with no obvious positive or negative terminals, just two wire clips at the bottom. One had one wire coming out of it (I think it was black/yellow), and the other clip had four wires coming out of it.

 

Why can't these things ever be easy?! At least I remembered to remove the back of the tach I was using, and make sure the switch was set to 4-cyl (it wasn't, it was set to 8-cyl). So I need more detailed instructions on where the green wire is supposed to go, because I can't find the "-" coil terminal, or the "tach output on the yellow diagnostic connector under the hood".

 

Thanks!

[socal1200r]

Trying to get this standalone tach to work is kicking my arse. Can someone look at these pics of the "coil", and the wires that are in and around it, and tell me which wire I need to connect the green tach wire to? I got the red wire to "+" on the battery, black wire to "-" on the battery, white wire unconnected to anything, so that leaves the green wire:

 

[socal1200r]

With some help from the local 4wd forum, I was able to locate the "-" terminal on the coil, after removing it and looking at it. So the standalone tach now has an rpm reading, and it's significantly different from the gauge tach. For example, at idle, the gauge tach is reading 800 rpms, but the test tach is at 1500. So I removed the gauge cluster, turned it around, and maybe it's me, but I'm not seeing any kind of "pot" switch to rotate, in order to adjust the gauge tach.

 

I even went thru the trouble of removing the gauge tach, but didn't see anything on the back of it either. Not wanting to give up just yet, since I got this far, I removed the small circuit board that has two wires going to the tach (the three screws above the two that hold the tach in). And low and behold, on this circuit board, there's a small white wheel that can be turned left and right. Since I didn't know which way to turn it, I turned it all the way to the left, put it and the tach back in the cluster, plugged in the main wires, and then turned the engine on. The gauge tach wasn't reading anything, and the test tach was around 1000 rpms, so I unhooked everything, pulled the board and tach from the cluster, turned the white wheel in the opposite direction, not quite all the way, put everything back together, and tested it again. This time I got a gauge tach reading, but it was off from the test tach by about 100 rpms. So one last time, pulled everything, adjusted the small white wheel, put everything back together, and now it was pretty much dead on, matching the test tach perfectly. Put the other wire harness on, secured the gauge cluster, put everything else back on, and now it's done.

 

Looking back, seems like the only way to have avoided this was to install a full gauge cluster from a 4-cyl XJ. But those weren’t available around here, so knowing what I know now, this would’ve been the last step when I did the gauge cluster swap a few months ago. So yes, for the tach to read correctly, it MUST come from a donor vehicle with the same engine! And recalibrating the gauge tach is a PITA, but it can be done. If I can do it, just about anyone should be able to do it!

 

Now to install that airbag helper kit (maybe tomorrow)…

[Eagle]

I'm looking for a photo. I know a friend had one several years ago, but he's in Greece and not on-line at the moment. Meanwhile -- http://www.naxja.org/forum/showthread.p ... light=tach

[socal1200r]

I'm looking for a photo. I know a friend had one several years ago, but he's in Greece and not on-line at the moment. Meanwhile -- http://www.naxja.org/forum/showthread.p ... light=tach

 

From reading this NAXJA thread, it sort of all makes sense now. The donor cluster came out of an '87 XJ 6-cyl, so that explains why there wasn't an adjustment screw on the back of the tach itself, it's on the small circuit board like what was mentioned, and what I found when I did it. Most likely, if the donor gauge cluster came out of an '88 or newer model, there would've been the adjustment screw on the back of the tach, and it sounds like adjusting it to work off a 4-cyl would've been MUCH easier to figure out, as opposed to the hit and miss method I had to use.

 

This was all a very frustrating experience for me, from getting the test tach to work (just where is the freakin' negative terminal on the freakin' coil?!), to adjusting the gauge tach to match the test tach. But, at least I can say I now know where all these things are, and I know how to do it. I probably would've easily spent over $100 having a shop recalibrate the tach, so at least that's $100 I kept in my pocket. I'm going to attempt to install the Airlift airbag helper kit I bought, and try to save some money on that as well. I've read thru the instructions several times, and it seems fairly straightforward. I bought a new electric drill/drill bits, and a portable 12V compressor to air up the bags, so I should have everything I need. If I was able to get this tach recalibrated, these airbags should be a snap...