Tach Fixed
#1
Tach Fixed
Well, I finally got the part I needed and got it installed. Thanks to 5.0 10 for posting the pic of the S-10 tach capacitor swap.
From that I was able to track down that capacitor on the Camaro tach.
It is right under the edge of the tach face at the 3250 RPM position, it is the larger of the 2 cylindrical items there. Just unsolider it from the PCB and install another capaciter .0033 uf 100VAC (Polyester film type). I got mine from Mouser Electronics http://www.mouser.com/ and the P/N for it is: 75-225P100V0. 0033
I was able to confirm through Winaldl that it was the tach that was reading incorrectly (by over 500 RPM), since both the ECM and Tach get the same signal from the distributor.
I put the new capaciter in the tach and fired it up and the RPM's are now reading right.
Hope this helps some others with this problem. And it beats the $125 that everyone wants to repair a tach.
~M~
From that I was able to track down that capacitor on the Camaro tach.
It is right under the edge of the tach face at the 3250 RPM position, it is the larger of the 2 cylindrical items there. Just unsolider it from the PCB and install another capaciter .0033 uf 100VAC (Polyester film type). I got mine from Mouser Electronics http://www.mouser.com/ and the P/N for it is: 75-225P100V0. 0033
I was able to confirm through Winaldl that it was the tach that was reading incorrectly (by over 500 RPM), since both the ECM and Tach get the same signal from the distributor.
I put the new capaciter in the tach and fired it up and the RPM's are now reading right.
Hope this helps some others with this problem. And it beats the $125 that everyone wants to repair a tach.
~M~
Last edited by Morley; 06-30-2002 at 02:38 PM.
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I am a little dense and my ability with electronics minimal...could you put up a diagram of the board or a pic that shows which component(s) need to be replaced?
Also will replacing that component correct a v6 tach for an 8? I did a board search but didn't find any solid answers on the issue.
Also will replacing that component correct a v6 tach for an 8? I did a board search but didn't find any solid answers on the issue.
Last edited by IROCmonkey; 06-25-2002 at 12:25 PM.
#3
Yes it will make a V6 tach work in a V8. I did however give the wrong position for the component that needs changed. It is at the 3250 RPM position not the 5750 RPM.
I tried to take a picture but the face plate is too close to the board and throws a shadow over the spot.
What you are looking for is a red/brown item (Capacitor) out near the edge of the board, it is about 3/4" long and 1/4" diameter. There is a smaller silver diode sitting next to it. Just unsolider the capacitor and bend the ends of it's wires up while the solider is melted, then remove it one end at a time and install the new one in the same holes and resolider.
~M~
I tried to take a picture but the face plate is too close to the board and throws a shadow over the spot.
What you are looking for is a red/brown item (Capacitor) out near the edge of the board, it is about 3/4" long and 1/4" diameter. There is a smaller silver diode sitting next to it. Just unsolider the capacitor and bend the ends of it's wires up while the solider is melted, then remove it one end at a time and install the new one in the same holes and resolider.
~M~
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OK finally got to the electronics store, got a capacitor, soldered it to the board and swapped the board onto my guage...problem is when I fired up the car the thing read waaaay too high instead of dropping to where it should be, so I either got a bad board or the wrong capacitor back to the drawing board. I will probably solder the cap onto my current board, which I know works and see what happens.
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Well after several trips to the electronics store, taking the dash apart half a dozen times and one burned fingertip I could not get the tach working, so I said **** bought a V8 tach from thirdgenparts and swapped the board onto my V6 tach....works like a charm. Funny thing is though, the capacitors on both boards are stamped with the same ratings...WTF?! oh well it works, I'm happy
Hmm I just realised my guage cluster is the biggest parts ***** in my car I have guages and parts of guages from 4 different cars in there, but the best part is all the faces and needles match
Hmm I just realised my guage cluster is the biggest parts ***** in my car I have guages and parts of guages from 4 different cars in there, but the best part is all the faces and needles match
Last edited by IROCmonkey; 08-06-2002 at 08:36 PM.
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#9
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Car: '89 Formula 350
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Hey what does it mean when your tach goes to like 3000 then kinda sticks and bounces around a little (200-300 rpm). Plus my speedo is off like 20 mph or so. More so the faster I go.
Any ideas???
Any ideas???
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Originally posted by My86Firebird
does this work with the Firebird Tachs as well?
does this work with the Firebird Tachs as well?
I installed some white face overlays last weekend, and just dummied them up on my old 86 V6 cluster first to see how they installed before attempting to demolish my 89 V8 cluster.
The 0 rpm point is in the same location on both faces. When straight up, the V6 tach reads 6000 rpm (with the V6), it is getting 6000 x 6 (36,000) pulses per minute at that reading. On the V8 face, straight up is only the 4500 rpm position, but it is still getting that same number of pulses per minute (4500 X 8 = 36,000).
This makes a cheap easy alternative to seeking out a V8 Firebird tach when swapping out a V6 for a V8. Find a V8 tach face, or install a set of V8 overlays and install them.
Pete
#13
I just converted my v6 tach to a work with a v8 by changing the .0068uf capacitor found under 5750 (above the oil gauge) to a .0033uf (332M) not the .068uf capacitor found under 3250. My gauge works Great with the v8 now.
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I changed the .0068 cap to .0033 on two different tachs pulled from 87 and 89 irocs and they still read high. You don't want to change the .068 or it will peg! Ok so has anyone yet experimented with the resistance chip or measured it pin to pin? I have very different readings between the two tachs I have and one is reading higher than the other so maybe it can be adjusted down. I have no schematics to work with.
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There seems to be some confusion here with which capacitor to replace. I have a v6 tach and need to convert it to a v8, which one do I replace, the 3250 one or the 5550 one?
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Re: Tach Fixed
can somone give me the capcitor ratings for a factory v6 tach need to convert a v8 tach to read right on a v6
#18
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Re: Tach Fixed
Can somebody explain what issues they were having with their tach that led them to determine that the cap was to blame? There is a very large thread devoted to the failed resistor issue, and from what I can see, this failed cap issue is producing some of the same symptoms. I'd like for us to be able to clarify specifically how to diagnose a faulty capacitor vs. a faulty resistor so that people with problems can be sure that they're doing the right fix.
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Re: Tach Fixed
Can somebody explain what issues they were having with their tach that led them to determine that the cap was to blame? There is a very large thread devoted to the failed resistor issue, and from what I can see, this failed cap issue is producing some of the same symptoms. I'd like for us to be able to clarify specifically how to diagnose a faulty capacitor vs. a faulty resistor so that people with problems can be sure that they're doing the right fix.
There could be issues with multiple capacitors going bad resulting in issues as well. The replacement of a resistor may be making up for the capacitors or other faults of the circuits. I can’t really comment on it any more specifically than that.
#20
Re: Tach Fixed
I have a 87 v8 Camaro that I've tried this in, and instead of being way off it now instantly pegs out to max rpm after the capacitor swap, any thoughts? I ordered this one http://www.mouser.com/Search/Product...225P100V0.0033 as suggested in the OP
Do you think I should also try that 90-92 tach fix with the resisters?
[update]
I went ahead down to radio shack and got 2 of those 100k 1/2 watt 5% resistance resisters to try that fix. Few things to note, older models don't have a separate removable board, that white designed chip is simply on the tach board with the for mentioned capacitor swamped before so its a bit harder to get to and work with. I however managed to cut the 2 pins needed and sauder the two resisters on it.
The new problem is now instead of being pegged at 7k it bounces between 500-1000 regardless of what the actual rpm is. So that fix either doesn't apply or needs some adjustments to work with my 87's v8.
Do you think I should also try that 90-92 tach fix with the resisters?
[update]
I went ahead down to radio shack and got 2 of those 100k 1/2 watt 5% resistance resisters to try that fix. Few things to note, older models don't have a separate removable board, that white designed chip is simply on the tach board with the for mentioned capacitor swamped before so its a bit harder to get to and work with. I however managed to cut the 2 pins needed and sauder the two resisters on it.
The new problem is now instead of being pegged at 7k it bounces between 500-1000 regardless of what the actual rpm is. So that fix either doesn't apply or needs some adjustments to work with my 87's v8.
Last edited by meltingsmoke; 07-24-2011 at 07:58 PM. Reason: update
#21
Re: Tach Fixed
I have a 87 v8 Camaro that I've tried this in, and instead of being way off it now instantly pegs out to max rpm after the capacitor swap, any thoughts? I ordered this one http://www.mouser.com/Search/Product...225P100V0.0033 as suggested in the OP
Do you think I should also try that 90-92 tach fix with the resisters?
[update]
I went ahead down to radio shack and got 2 of those 100k 1/2 watt 5% resistance resisters to try that fix. Few things to note, older models don't have a separate removable board, that white designed chip is simply on the tach board with the for mentioned capacitor swamped before so its a bit harder to get to and work with. I however managed to cut the 2 pins needed and sauder the two resisters on it.
The new problem is now instead of being pegged at 7k it bounces between 500-1000 regardless of what the actual rpm is. So that fix either doesn't apply or needs some adjustments to work with my 87's v8.
Do you think I should also try that 90-92 tach fix with the resisters?
[update]
I went ahead down to radio shack and got 2 of those 100k 1/2 watt 5% resistance resisters to try that fix. Few things to note, older models don't have a separate removable board, that white designed chip is simply on the tach board with the for mentioned capacitor swamped before so its a bit harder to get to and work with. I however managed to cut the 2 pins needed and sauder the two resisters on it.
The new problem is now instead of being pegged at 7k it bounces between 500-1000 regardless of what the actual rpm is. So that fix either doesn't apply or needs some adjustments to work with my 87's v8.
#22
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Re: Tach Fixed
i tried this on my 1989 v8 tach.its now pegged at 7000.i wonder if this was a 'convert your tach from v6 to v8 post'the whole time.its also confusing.
[quote]
Yes it will make a V6 tach work in a V8. I did however give the wrong position for the component that needs changed. It is at the 3250 RPM position not the 5750 RPM.
I tried to take a picture but the face plate is too close to the board and throws a shadow over the spot.
What you are looking for is a red/brown item (Capacitor) out near the edge of the board, it is about 3/4" long and 1/4" diameter. There is a smaller silver diode sitting next to it. Just unsolider the capacitor and bend the ends of it's wires up while the solider is melted, then remove it one end at a time and install the new one in the same holes and resolider.
[end of quote]
is it the capacitor at 3250 or 5750?on my tach the silver diode is beside the 5750 capacitor.maybe morleys tach was different than mine.
[quote]
Yes it will make a V6 tach work in a V8. I did however give the wrong position for the component that needs changed. It is at the 3250 RPM position not the 5750 RPM.
I tried to take a picture but the face plate is too close to the board and throws a shadow over the spot.
What you are looking for is a red/brown item (Capacitor) out near the edge of the board, it is about 3/4" long and 1/4" diameter. There is a smaller silver diode sitting next to it. Just unsolider the capacitor and bend the ends of it's wires up while the solider is melted, then remove it one end at a time and install the new one in the same holes and resolider.
[end of quote]
is it the capacitor at 3250 or 5750?on my tach the silver diode is beside the 5750 capacitor.maybe morleys tach was different than mine.
Last edited by zenish; 12-19-2011 at 03:02 PM.
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Car: 1989 camaro rs convertable
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Re: Tach Fixed
ok.i got my tach almost right now.i did as this post said.https://www.thirdgen.org/forums/elec...meter-fix.html .i ended up using a 100k and two 47k resisters.according to my scanner my tachs now right at idle,100 rpm low at 2000 and 200 rpm low at three thousand.close as i could get without using a variable pot.
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Re: Tach Fixed
what was wrong with the tach that you had to change the capacitor. mines not working at all since the rebuild.
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Re: Tach Fixed
Sorry to bump an old old thread. I just want to be sure im comprehending this right since im no electrical engineer.
To fix an 89 or earlier Tach all you need to do is replace a red capacitor near the 3k mark on the circuit board?
"The stock tachs in these cars are notorious for reading incorrectly. The usual problem with the 82-89 Camaro tachs is a capacitor located on the back side of the tachometer face."
Or do I need to do what it says here... to clip the 4 and 10 resistor pins? There is a white and black resistor on the earlier style tachs.
https://www.thirdgen.org/forums/elec...ml#post2836660
To fix an 89 or earlier Tach all you need to do is replace a red capacitor near the 3k mark on the circuit board?
"The stock tachs in these cars are notorious for reading incorrectly. The usual problem with the 82-89 Camaro tachs is a capacitor located on the back side of the tachometer face."
Or do I need to do what it says here... to clip the 4 and 10 resistor pins? There is a white and black resistor on the earlier style tachs.
https://www.thirdgen.org/forums/elec...ml#post2836660
Last edited by chevman24; 03-02-2013 at 12:41 AM.
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Re: Tach Fixed
I have the same question as chevyman. 88 305 iroc. Do i just need to replace the capcitor or do i also need to mees with the circuit board?
#30
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Re: Tach Fixed
Greg,
I just replace the resistor with a set value for the V8 cars found in one of the threads. Oh I found it. I used a 190k ohm resistor on it.
Can you change a V6 tach into a V8 tach with the same resistor swap or do you have to do other modifications to it? I have a 6000rpm tach and I don't know if it's a V8 or V6 tach. I assumed it was a V8 so I put the standard resistor in it for the V8's.
I found the thread:
https://www.thirdgen.org/forums/elec...-89-tachs.html
I just replace the resistor with a set value for the V8 cars found in one of the threads. Oh I found it. I used a 190k ohm resistor on it.
Can you change a V6 tach into a V8 tach with the same resistor swap or do you have to do other modifications to it? I have a 6000rpm tach and I don't know if it's a V8 or V6 tach. I assumed it was a V8 so I put the standard resistor in it for the V8's.
I found the thread:
https://www.thirdgen.org/forums/elec...-89-tachs.html
If you dont have a function generator, the following resistor values can be used directly:
V6 tach = 256 kOhms
V8 tach = 192 kOhms
V6 tach = 256 kOhms
V8 tach = 192 kOhms
#31
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Re: Tach Fixed
My stock tachometer is twice as fast as the aftermarket tach we put on top of my dash. How would i fix this?
#32
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Re: Tach Fixed
I did what Dimented did in his thread, but I went on ebay and bought the small 190k resistors so it would take up as little space on the board as possible. I snipped the leads on 4 & 10 IIRC, desoldered the leads, cut the leads as short as I dared on the 190k and resoldered them into the holes.
#33
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Re: Tach Fixed
https://www.thirdgen.org/forums/elec...-89-tachs.html
I did what Dimented did in his thread, but I went on ebay and bought the small 190k resistors so it would take up as little space on the board as possible. I snipped the leads on 4 & 10 IIRC, desoldered the leads, cut the leads as short as I dared on the 190k and resoldered them into the holes.
I did what Dimented did in his thread, but I went on ebay and bought the small 190k resistors so it would take up as little space on the board as possible. I snipped the leads on 4 & 10 IIRC, desoldered the leads, cut the leads as short as I dared on the 190k and resoldered them into the holes.
#35
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Re: Tach Fixed
Thanks, I was trying to get as close to 192k as possible. I used a 100k, and two 47k resistors spliced and soldered together (in the shape of the letter Z). Because of the 5% tolerance of the resistors, and each resistor being slightly under-value, I am at 190.8k ohms. I couldn't run it long yesterday because I have the transmission out and open headers, but it's only 200-300rpm off from from what my ECU says. WAY better than the 2000rpm variance that I had previously.
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