ElectronicsNeed help wiring something up? Thinking of adding an electrical component to your car? Need help troubleshooting that wiring glitch?
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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.
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.
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.
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.
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.
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.
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?
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.
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"
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.
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.
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.
Quote:
Originally Posted by lucky14
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.
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
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 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).
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 ?
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..
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...
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
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
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
__________________ '91 Z28 convertible w/305TPI WC T5 (no more auto)
"Nothing screams more of poor craftsmanship than wrinkles in your duct tape!"
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!
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?
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.
