OK, if you comment, please keep in mind this is a 1994 Model. (I don't know if there is a difference between the 93 and the 94).

My tach is starting to go wonky, yesterday it sat at 3000 while the engine sounded and felt like idle. After the car warmed up, it seemed to operate normally. Later that day, after the car had sat for a hour or so. The 3K act repeated, but this time, instead of just sitting, the needle started to slowly rise to 4K while driving. After a few minutes it again settled down and seemd to work OK.

Of course Mazda says $750 for a new tach, so I guess it is time to try to find a used tach that I can repair and put in place of the original. Before doing so, I will wait to see how bad it gets.

In the meantime I have been doing a little research and have these questions.

1) Tach cold solder joints. Not experienced at soldering, so is it easy to FU what I already have? If so, if I remove the tach, is it reasonable to expect that a computer or tv repair shop can resolder the tach cold joints and replace the two condensors?

2) Some posts say you just have to "Drop" the steering column to get the cluster out? The FSM says to remove the Air Bag and Steering wheel to get to the cluster. I don't relish the thought of mucking with the air bag. Is dropping the cluster doable on a '94 or will I have to remove the airbag and wheel?

3) Some posts say that the diagnostic port can be read for troubleshooting, the FSM says that the tach has to be removed and a temp put in it's place to test. Since this is an intermittent problem at this time, removing the tach to see if it is bad is impractical, is there something I can learn from the Diagnostic Port?

4) The '94 tach reads from the speedometer and CPU, the manual also says to check the connection at the CPU. My questions here are: (a) if I have never had the CPU out, what are the chances that it has become loose? (b) if I check the connection, is there some electrical connection cleaner spray I should use to improve the connection? Or just reseat the connector?

Any insight from someone who has fixed their tachs would be appreciated.

 

I see no reason why you would have to "drop" the steering column to remove the instrument cluster. What those posts probably meant was that you have to "drop" (remove) the top and bottom cover for the steering column/ignition switch, which is basically a plastic shell. I also don't see how this could be radically different from '93 to '94.

 

On my Maxima, there are two bolts that hold the steering column up under the dash. If you remove these bolts the steering wheel lowers down and out of the way of the gauge cluster. On an FD it may be a similar situation, I recommend that you try it that way first.

Yes, a regular electronics repair shop will be fine for doing the repair. Of course, if you have any friends who are electrical engineers or electrical repair, it's a pretty quick and easy job. I actually chose to learn soldering by repairing some Bose amps, so if you choose to invest $30 for a basic soldering kit then I think you stand a very good chance of a successful repair. The key to not damaging things is to not leave the iron on any joint for more than a few seconds. Excess heat damages parts more than anything else, and if you keep that in mind it's no big deal.

If you haven't downloaded the body electrical manual from the sticky, that's where the official troubleshooting info is.

Dave

 

Thanks Kento, Dave,

I have not been in these area yet, so I wanted to get opinions from those who have.

Not removing the Steering wheel and the air bags will be a blessing.

So, I will go ahead and try to get the cluster out with the method you described Kento (when the time comes).

I do have some experience with soldering (stained glass - see avatar), so I am not a total noob there. I just want to be sure not to destroy the unit. So, I will give that a shot too. I'll just have to find a way to make sure my hands don't shake

Thanks again.

I think I will do a picture write up as I remove/repair/replace stuff.

 

I love soldering! Shaky hands has to do with your blood sugar as well. Don't pull any all-nighters or skip any meals the day before. I've even stopped soldering to grab a bite to eat, and noticed that my hands that were more stable after. If you really have a problem with shaky hands, rest your elbows on the table or use both hands even.

Another thing, be sure you've got the right sized tip on your iron. You've probably got a pretty large & flat tip for mechanical stuff like stained glass, but an electronics store will have very fine tips, smaller than a ball-point pen. Don't use that fancy 'silver containing' solder, because it's got a higher melting point which could be bad for electronics: plain tin/lead solder is best. Use plenty of solder when tinning the tip of the iron, because it will transfer heat better.

If you're soldering on that soft flexible plastic ribbon, you might want to use a pair of tweezers or a small piece of aluminum as a heat sink: press the tweezers just a few mm away from your solder joint, and they'll absorb the heat rather than letting it travel through the material. Dip the tweezers in water if your material is still heating up too much.


PS, I've removed the gauge cluster in my '94, without taking the steering wheel off. I did lower the steering column using the two bolts that dgeesaman mentioned. The cluster pulls straight back (towards the rear of the car) and will pop out. You've got to tug pretty hard on it. The hardest part is you've got quite a few electrical connectors to remove, and not a lot of space to do it. Here are some photos:








-s-

 

On my '93 touring, I didn't have to lower the steering column. The gauge cluster popped out with some maneuvering; IIRC, the clearance problem in my case wasn't the steering column, it was the close proximity of the windshield to the gauge cluster cover.

 

Thanks once more...

I'd appreciate a make and model number for a soldering Iron, the type of solder to be used, a name for a tool to remove old solder, yada, yada, yada.

I'll go get this stuff and go for it. Other than linearizing the water temp anything else to be done under there?

 

where exactly are these tach cold solder joints? my tach is dead as well...could someone post me pics? thanks

 

I just finished doing this and the first time it took me an hour and the second and third time it only took me about thirty minutes. I tried the solder thing and it didn't work for me, so I just replaced the tach with another one, which works perfect. If you can get a tach (doesn't matter where it comes from as long as it's out of a 93,94,95 or JDM) then the only thing you will need to do is replace the face and you’re done. Do a search and you will find the instructions on how to remove the dash, which is dead on. Good luck and if you have any questions just pm me or post on this thread. I went through the same thing with not wanting to take the dash apart, but once you do it. IT'S A PIECE OF CAKE!!!

https://www.rx7club.com/showthread.p...highlight=tach

 

Just something to keep in mind if you have a 93 (I believe you said you have a 94) any way the 93 tach is graduated in single incriments of 100rpm where the 94 and 95 are incimented in units of a hash mark every 5oo rpm's not in 100. Mazda felt the hash marks every 100 rpm's was clutered and went to units of every 500 in 94 and 95. Sorry for repeating myself, just wanted to be clear on this.

 

interesting