i'm afraid to make a mistake because i have seen this version :



& this one :




i'm totally confused....
if someone can explain me with pics it would be very kind
thanks a lot in advance!!

see you soon

Tof

 

you only need to cut one pin on the chip.. this will do.







don't worry about the other side of the chip, or the trace on the bottom of the board.

then solder the resistor(s) like this.




where this pic goes wrong for me, is its shown soldering the resistor leg to the chip pin and board, you don't want that or you will undo what you just did by cutting the leg off. make sure on the side with the cut pin that you are soldering to the board and not whats left of the pin coming out of the chip and you should be good.


its much easier than the pics make it look. pretty much the chip is a 200k resistor across pin 4 and pin 10. the reason we snip on of the pins is because sometimes the chip doesn't burn all the way out, so to bypass it 100% you snip a leg. then jumper over the top with the replacement resistors of the value the chip was before it went bad.




if i missed anything, i'm sure another member will post up. but this is how i did mine and it worked.

 

Thanks for your fast response !

so do i understand well this time ! ;-)



but how can i do with only 1 resistor for 195/200 Kohm i only find 100Kohm and 220 Kohm, could i solder 2x 100Kohm on the same place ?
Thanks

tof

 

yes you can use 2 100s in line or just out the one 220 in there. it will be close. if you want it dead on, I used a 100k resistor and a 100k adj pot. but its not needed.

 

thanks alot :-)

 

Make your life easy and solder between the pins on the back of the board instead of the front like the pics above. Just cut one of the 4 and 10 pins, turn the board over and put your two resisters between them. Its much easier and there is way less room for error.

 

ok thanks for the tip ;-)

tof

 

Another Tach fixed. Drove around town trying to fine someone to do the sodiering...after I saw how small and close together the legs were. no one would touch it.One guy said to leave it and he'd do it for $50 bucks.....I passed. Bought the snips at radio shack and muddled through it myself. No way I could sodier from the side with the chip and not have it touch another lead...but I was able to do it from the back side. I now Have a working tach and am very happy. Thanks Blue... If you ever want to visit the NH seacoast send me a PM. Mike

 

Well, I hooked mine up tonight too. Works like a champ. If there is anyone in the NH area that wants this done I can hook you up with the right size resistor and installation if you bring it by.

 

Does anyone know the resistor value to use for the V6?

 

fixed mine tonight in 1 hr, learned how to solder too!

 

My tach was completely dead, it never moved at all, so I had my doubts. I stacked two 100k's and in about 45 min it was fixed, so thanks to the dude who figured this one out.

 

Here is the way I did it. I would recommend this way. Much easier to solder in and looks cleaner.

 

Hey groundrat - what are the specs on the resistor that you used? Definitely looks like a good clean job...

 

looks like a 190k or 196k to me. Same exact way i did it except i used 2 100k's in parallel.

 

It is a 196K ohm carbon resistor. they can be had dirt cheap even at radio shack. Thanks for the compliment. If you want yours done I can walk you through it.

 

anyone know where I can get another chip ? I did the fix for it however other resistors were weak and now my car smells like burnt chip board .

 

Unfortunately I do not. But The burnt electronics smell is probably from the IC chip next to the resistor chip. Can you pull it and post a picture? What does the tach do now?

 

hopefully this works
the tach is now on 0 rpms instead of 7000

 

Let me look at mine. I may be able to tell you what the value of that is. You may want to post in the wanted section for a junk gauge cluster or the board. I could probably fix it if you sent it to me.

 

Glad to see this thread is still helping folks along
Excellent example of the community.

 

I put 100K+47+47+2= 196K in series. Now my car idles at 500-600 RPMs, what did I do wrong? Please help! Thanks!

 

First of all you need to make sure what your car is really idleing at. second of all a resistor does not always show as much resistance as the package it comes in represents.

Like on my car for instance i ran two 100k resisters, BUT In reality its only about 194k-197k something like that. And yes just that little bit will make a difference. My guess is you running exactly 196k of resistance is your problem because in reality your probly a liitle to low. If I were you I would try 2 100k resistors because it will probly bring it up a little bit.

Keep in mind not everybodys car is the same. Some take more and some take less. You just have to play with it a little bit to find the G-spot "so to say"

Post back with any questions or if ya fix it. jay

 

Thanks! I'll try 2x100 next. I'll post back.

 

groundrat either way would work I just really want ti fixed for cosmedic reasons . What ohm and resistance is it??

 

when I first did the fix I had a 150 and a 47 which is 197 cool right ??No I took my ohm meter and the 150s were actually 148 the 47 was 47 so 195 . well just as soon as I install it it worked so so then smoke , I checked the resistance and it had dropped to 168 . So when heat is applied it drops resistance and it can be lowered just by useing it . Maybe someone here can tell me which resistor is the best . I like the carbon resistor idea but would LOVE a radio shack part number . PLEASE !!

 

I am disassembling my board tonight. Sorry for the delay. It sounds like you have a short on the board though. Double check all the solder joints to make sure nothing is bridged. If the short isnt fixed, the big resistor will pop again.

 

heres exactly what I used....100k-ohm 1/2 watt carbon film resisters with a 5% tolerance. Part# 271-1131 cost = 99 cents. comes in package of 5.

 

I 'll try this, just gotta get to radioshack tomorrow morning. Thanks!!

 

I found 100K 5% 1/4watt at home. Do you think they will work, or should I get 1/2 watt ones? Thanks

 

they will work as long as the tolerance is around 5%

 

There is a very reputable shop here in Richmond, VA (my dealership uses them for cluster repairs). The shop is very friendly and does accept mail orders and core exhchanges.

I have e-mailed the owner about my Tach... buried at 7K RPM when the engine is running. but falls to the 0 mark with the engine off key on. I am and neither is the owner convienced its not a problem in the distributor. However, he has repair inaccurate tachs (100-500 +/-) in late 3rd gen-ers. I told him I am going to replace my dist. and see what it does.

However, it doesn't repair it he agreed to look at it... and I told him about all the info on here and he is willing also read our info on the capicator/resistor bed on the sub PC board. c

Check him out if you have the $ to fix your inst. cluster before I save up $ for my distributor.

http://www.instrumentclusters.com/

 

Before you spend the money and time replacing a good distributor, go find someone with a scan tool or a laptop and ALDL cable. Check to see if the computer is getting the correct tach signal. If the computer sees the corect RPM it is your cluster.

 

Oh yea I know... I got to thought the ol Snap on Modis on it and see what the tach signal looks like.... but with 200K on the chassis... I am not so sure it isn't due for a dist. anyhow! thanks

 

I don't know if it's absolutely the BEST, but my 1Mohm potentiometer is still producing a steady signal through the tach. I have re calibrated the systems twice since the install. I just pop off the dash bezel, hook up my timing light (that reads RPM) and match the tach to the light reading at idle, 2000 and 2700 rpm.

The pot. is probably the most accurate, solution, but also MAY require more upkeep.

You could get one of the 100ohm mini pots and run it in series with a 150 ohm resistor from radio shack. The minipots are smaller and seem to hold their setting better (harder to bump the dial, since it's recessed).

I will probably do the later to mine eventually.

Best of Luck!

 

Okay, my 92 305 reads 1200 at an 800 idle, and 4200 at 2800. What part do I need to look at? What resistor?

 

Hi guys !

Well after i have received from my friend in USA (L.A) the resistors (0.99$ for 5 !) i do the tip today and it works !!! Excellent !! THANKS for the member who share this tip with us !

well some pics :

here the resistors (cost me less to buy it in USA and ship to France than buy them in France !!)


then i have welding two resistors together and after i have cut the leg on the chip, i weld on the plate. Like you can see i'm not an expert in welding !! it's not very clean but it works !




& finally in the cluster of my 350 Ci Z28 1991




Now because i have this cars since 3 years and half and the RPM never work wel, could someone here can tell me if this is normal please ?

Idle = 800 Rpm
30 miles with D = 1500 Rpm
80 miles with OD = 2500 Rpm

it seems with full throttle the gears change at 4250/4500 Rpm
is that ok ?

thanks

Tof

 

hey guys, joined the forum just for this topic.. i've got a 90 vette with a problem of tach pegging out at start up then dropping to 0 and staying there... i've not had a chance to pull the board to check it yet.. i've seen a few people post with similar problems but havent seen if this fix took care of it.. if anyone else has had this issue and knows if it will or wont fix it please let me know..

 

That sounds about right. Stock 700R4? Most shift around there.

 

hey guys, thought i'de post up what i've found... my 90 vette had a different style board.. one huge board as big as the gauge panel.. is does use the same resistor chip.. i followed directions and recommendations as all the others and my tach seems to be working fine now.. as stated it would peg out on start up and then back to zero... now its showing idle at a little less than 1000... i'll test drive tomorrow... thanks for everyone thats had input on the issue...

 

I didn't realize that was my first post here

Anywho, I'm actually working on a tach from an '87 Monte SS that I'm using in my '81 Malibu - which, coincidentally, has the same resistor pack. I'm currently on a quest to find an actual diagram for the tach's PC board. If I find one I'll try to remember to post back here as well

 

thanks for your info about RPM :-)

tof

 

You might want to start a new thread for the older tachometer. This thread is dedicated to fixing the 90-92 "half-moon" gauges.

Thank you
Lou

 

I just finished mine and no luck. The tach moved a little when I started her up but that's it. I soldered a 220 ohm to the back. Any suggestions? I cut it out and I'm gonna try it from the top.*******DISREGARD******I had a 220 ohm not a 220k ohm resistor duh. I'll get it right this time!

 

That 220k will read high. You really need a 196k. Just FYI

 

I agree 220 is to much. I don't know why your trying a 220. Read back through the posts......195k-197k seems to be around the magic numbers.

Remeber......it doesnt really matter what wattage it is as long as you get one with a 5% tolerance.

 

yeah...I know. I'm gonna pick up some 100's tomorrow. It seems like everyone like two 100's in line. Thanks

 

Just got it done and it works like a champ! I replaced all the gauge lights while I was in there as well. Thanks!

 

Well I did the repair with the two 100k ohm resistors and it works great. The repair fixed the tach and now my temp guage doesnt peg out and get stuck, so two birds with one stone.

The only downside after the repair is now my fuel guage stopped working (pegged out). Anyone else had this issue?

 

My fuel gauge didnt work what-so-ever until i did this fix. IIRC The reason it wasnt working was because of poor contacts when the cluster was put back into the dash. I would Try pushing the cluster into the dash with the key on to see if the needle jumps.