How to: 3000 RPM Tach Fix

[qtrmill]

If you have a tach that you think has gone bad just because it is always up around 3000 rpm? It's not busted - just needs some old fashioned TLC... Here goes:

You'll need:
T-20 and T-15 Torx driver or bit
Something to pry the dash trim off
Soldering Iron and maybe some solder/flux

1. Start with the basics... pull out the ashtray as far as it'll go then unscrew the two T-20 screws. Pull the ashtray out and set it on the floor.


2. Gently (emphasis on GENTLY - these trucks are getting on in their age and the trim can be brittle) pry out the driver's right A/C vent and the 4X4 controls/fake vent. For some reason, my 4X2 is prewired for 4X4 and even has bulbs behind the 4X4 lights in the dash?!? Disconnect this and set on the dash.


3. Key in and turn to unlock the shifter. Shift all the way down to "L". Then, even gentler than before, pry the trim piece off the mounting tabs and take it all the way out. You may need to turn the whole thing to the right to get it to come all the way out like I did.


4. Remove 7 x T-15 screws that hold the plexi cover in place. Remove the plexi along with the black shroud in between the dash and the plexi.

5. Slowly pull the tachometer out of the cluster. Just prying with your finger works best.

6. Put the tach down on a cloth or something soft so the dial/needle don't get damaged. Take a look at the soldering on the "top left" of the circuit board. You'll more than likely find some cracks in one, two, maybe a lot of them. These are the ones that need repair - duh... :

7. Warm up the soldering iron and slowly fill the cracks up. I managed to get away with using just the factory solder. If you get impatient and pull the solder off with the soldering iron, you'll need to re-fill with your own solder.


8. Press the tach back into the cluster and fire the engine up - after putting it into Park first, of course...

9. Then, shut off the engine, put it back in "Low" and go step by step backwards, putting all the bits back in the dash.

Time involved - about an hour.

If you're like me and waited YEARS to fix this, try not to stare at the newly working tach while you drive!

 

[kraylake]

you guys are awesome. I fixed my tach exactly as described above.

 

[Tbars4]

...Great information...:biggthump

 

[TedJ]

Good info...

The only thing I would say is don't try and pry out the 4x4 switch/vent. You can pull the trim with it all together and just unplug the wiring harness with the entire trim pulled away. Much less risk of messing up the plastic imo.

 

[blhenry]

Thanks!

I was a bit cautious about trying this, since I've never soldered anything in my life, but tried it today, and the tach works perfectly now. Thanks!

 

[1Byounkin]

Mine tach is staying at 6,000 when running and driving. But traveling at 70mph the needle moves to 5,000. After the engine cools the tach will work until hitting 65 - 70 mph. Will mine have the solder messed up? Gas gauge stops to the right of "F" never moves. ALL of this started at the sametime.

 

[qtrmill]

Tach Soldering

Sounds like you may have some failed soldering. Generally speaking they fail to around the 3000rpm point, but I suppose this could differ. Sometimes mine would creep up to 4000ish but then come down later. If it goes straight up with the engine off but key on, then it's probably soldering.

As for the gas gauge, sounds like a stuck sender but again, most of the time they fall to E not stick at F. The dash panel with the engine gauges could be loose a bit, or the actual sender wiring might be damaged. Dropping the tank to do this is waaaay more of a pain than taking the dash out though - and you need to check the tach out anyways, so I'd start there.

 

[FirstExplorer]

Good thread! Now I can get that mummified crane fly out of there. He's been in there for 15 years.

 

[FIND]

Same thing the Neon guys have to do... Good to remember if I ever get one with a bad tach.

Good thread! Now I can get that mummified crane fly out of there. He's been in there for 15 years.

 

[dking]

Great Thread mine his just started the 3000 rpm dance. Thanks for posting the info.

 

[jasea]

Whoop & Thanks

This is a great post. I have had many trained mechanics attempt to fix my tach problem for years and all failed, usually claiming bad sensors or wiring. I followed the above thread and now mt "92 EB is running great. Fixing the tach and getting the correct rpm reading also stopped all problems with labor knock due to preinigition. The whole job tokk less than one hour.

Thanks and Best regards,

 

[mr cribb]

Roadrunner777 suggested this thread to me.... Thanks!

Interesting.... I'll have to look at my circuit board.

However mine doesn't stick at 3k, it stays at 0, only after a 1/2 throttle acceleration does it move to the 3k range for a few seconds, before dropping to zero again. For my problem is it possible to be the same issue as above?

 

[ndavis426]

i have a similar issue on my dads 2000 explorer xlt w/ the sohc 4.0 is this the same thing causing that?

 

[jjon90]

Great info! Got mine done today.. Thanks for posting!

 

[wantdeath]

I did this, and it works. I had to do the same thing awhile back to my old neon. thanks!

 

[mr cribb]

I finally fixed my tach today.... I installed one from a 94 XLT. I tried soldering the broken spot and that failed. I'm guessing mine fried when the light switch burnt up.

Either way all is well again, good post though and glad it works for some folks.

 

[dking]

Just repaired my tach today. Works great. Thanks qtrmill for the thread.

 

[mlburgoon]

I hate for my first post to bring up an old thread, but I just bought a 1992 explorer. This fix worked on it, and I wanted to say thanks.

 

[Tbars4]

..That's what these old post are for...Glad you found it and that it helped resolve your problem...:biggthump

 

[GeekyTechyCool]

Yeah don't feel bad, I just joined myself and have the same problem. Now that this popped up in my google search I'll be trying it this weekend.