tachometer problem on 1977 monza

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tachometer problem on 1977 monza

Postby gm_fan » Fri Dec 03, 2010 1:40 am

I have problems with my tach on my monza spider. I reads higher that it should. I installed a nos tach filter and it did not make any difference..The strange thing is maybe 2 times out of many that I have started the car, it did read correctly. After I shut it off , it went back to its former high indication. It reads approximately 1.5 times higher that it should..Any suggestions? thanks in advance..gm_fan
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Re: tachometer problem on 1977 monza

Postby MIKESMONZA » Wed Dec 15, 2010 1:04 am

JUst a thought;
Conections
#1,,,Dirty or loose Brass clip piece is Spred inside of
maybe a faulty plastic Clip,>>> at distributor out put pick up>>> at cap next to power wire!
espeacialy if Coroision or Mositure is present !

,,,#2 bad ground in Cap on Coil >>Loose screw holding coil Down inside top cap

#3 a out put Clip Broken Wire internaly !

,# 4 ,,,,,loose bolt (hardware) fastening on Intake throtle Bracket
(They will work some tines with out a ground!)

#5,,,,,,too much paint to the Clamp on the filter Mount on the accelerator
or a>>>>> problemn behind Dash Cluster at back of factory Dash Tach !

They are not realy reliable Tach's after years of Service in most cases!
but we like them to work ! :th:,,,
They are cosmeticaly appealing! :dance:
Mike
Last edited by MIKESMONZA on Wed Dec 15, 2010 9:27 pm, edited 1 time in total.
355,SBC,700R4Trans,3.42 rear,Sandersons,Edelbrock,Carb,Intake,Griffin,1,900 rpms at 60 MPH Highway Cruise Car.
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Re: tachometer problem on 1977 monza

Postby marco_1978_spyder » Wed Dec 15, 2010 7:22 am

Pull the tach out of the dash.

On the back you should find a plastic clip usually orange or red that fits inside 1 of 2 small recangular holes.

-If you swapped from a 4cyl you may not have this piece at all but you still have the 2 holes.

This plastic piece holds a small piece of metal to the solder on the board around 1 of the holes bridging a gap.

When this piece is loose, it sometimes reads correct when there is proper contact, and other times reads high when contact is lost.

You can bend the piece of metal on the plastic clip for better contact, or better yet just solder the piece on there permanently.
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Re: tachometer problem on 1977 monza

Postby gm_fan » Wed Dec 15, 2010 11:30 pm

I will give it a look. The wiring is all like new, with absolutely no dirt or corrosion..the car only has 6 thousand miles since new. Just have seen the tach work correctly 2 times..I put a nos tach filter I purchased from clyde biagi , and though that might be it, but to no avail. Thanks for the tips...., by the way , its an original v-8 car, but it also 33 years old, so probably could be several possibilities ..thanks again,, gm_fan
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Re: tachometer problem on 1977 monza

Postby my79monza » Mon Jan 03, 2011 11:40 pm

gm_fan wrote:I have problems with my tach on my monza spider. I reads higher that it should. I installed a nos tach filter and it did not make any difference..The strange thing is maybe 2 times out of many that I have started the car, it did read correctly. After I shut it off , it went back to its former high indication. It reads approximately 1.5 times higher that it should..Any suggestions? thanks in advance..gm_fan


Maybe I don't quite understand the issue.
The tach won't always go to 0 with the key off but should do so the second you turn key on.
At least thats what happens on my 80.
Does it read fast in your opinion after engine is running? is that the issue?
Merle
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Re: tachometer problem on 1977 monza

Postby gm_fan » Tue Jan 04, 2011 11:54 pm

Yes , when the engine is running , it reads approximately 1.5 times the right reading,, when you turn the key on it goes to zero . Like I said before, I have seen it work correctly about 3 times only...gm_fan
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Re: tachometer problem on 1977 monza

Postby marco_1978_spyder » Wed Jan 05, 2011 9:33 am

Did you check the clip on the back that I mentioned above?

It'll fix it.
1978 Monza Spyder V8 4speed, posi
1978 Sunbird Formula V6, 5 Speed, Hatchback
1980 Sunbird Hatchback 4cyl, 4spd.
2006 Chevrolet Aveo 5 speed Hatchback
Yes, you can refer to me as Mark
Please visit my blog... http://chevymonza.blogspot.com/ Follow if you like!
Featuring special guests; Carl Beraytor and Ray D'atore

My Red spyder now has a youtube channel please Like and Subscribe!!!
https://www.youtube.com/channel/UCOzzSR ... ISuing7KLA
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Re: tachometer problem on 1977 monza

Postby gm_fan » Wed Jan 05, 2011 10:38 am

actully I have not had time , but that is my next step,,thanks Mark
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Re: tachometer problem on 1977 monza

Postby cjbiagi » Wed Jan 05, 2011 2:01 pm

Have you looked inside the distributor to make sure everything is tight? If everythig=ng else checks out maybe there is something flaky with the module or pickup.
Clyde.........75 Monza 2+2
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Re: tachometer problem on 1977 monza

Postby gm_fan » Wed Jan 05, 2011 7:25 pm

Yes, the distributor is new, and actually put it on my buddies machine to check total advance because I am not using the vacuum advance , so we changed the springs for the correct curve with 36 degrees at 2500 rpms,,I think its probably the circuit board on the dash cluster hopefully,,thanks,,,,Mark
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Re: tachometer problem on 1977 monza

Postby cjbiagi » Wed Jan 05, 2011 7:46 pm

Did it do it with the old distributor?
Clyde.........75 Monza 2+2
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Re: tachometer problem on 1977 monza

Postby gm_fan » Wed Jan 05, 2011 11:06 pm

yes ,no change between distributors..I feel like its the tach, or close proximenty..I want to get the car 100% complete by spring for some shows and cruises,,gm_fan
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Re: tachometer problem on 1977 monza

Postby my79monza » Wed Jan 05, 2011 11:51 pm

what color is the needle on the tach, red or white?
Merle
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Re: tachometer problem on 1977 monza

Postby gm_fan » Thu Jan 06, 2011 12:03 am

I keep the car inside at my transmission shop. I will look and let you know tomorrow,,thanks Mark
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Re: tachometer problem on 1977 monza

Postby gm_fan » Thu Jan 06, 2011 9:01 pm

The tach and speedometer have the red line pointers,,thanks Mark
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