sun super tach ll question for ya

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i have a new SST2 and a MSD blaster coil . i have the tach set at 8 cylinders , the red at hot and the black at ground and the white is not connected up (face light) and the green is on the negative side of the coil.when i start the car , the needle idles at around 700 RPMs. when i get in and go the needle drops in RPMs and comes back up when i slow down.WTF ? its like it is working backwards. is my tach jacked up? am i missing something here? tachs are a no brainer but this thing has me stumped.would it act like that if the ground and hot were switched? it seems to me it wouldnt work at all.is it a bad ground? or can i not use it with the MSD coil? i know this sounds wack but im at a loss lol .any help would be great thanks.
 
I ran into the same thing, had an old Sun tach and MSD, they don't work together. MSD makes a Tach Adapter, you wire this in and then your tach will work. I tried this but must have got the wrong one cause it didn't work. My tach worked fine with the MP ignition. Easy fix, I installed a vintage Auto Meter and it works fine with the MSD. I think the adapter was $40-50 too. Here is a link to what the part looks like, you will need the right one.

http://www.ebay.com/itm/MSD-8910-Ta...Parts_Accessories&vxp=mtr&hash=item588c31e982
 
66340SEDAN said:
I ran into the same thing, had an old Sun tach and MSD, they don't work together. MSD makes a Tach Adapter, you wire this in and then your tach will work. I tried this but must have got the wrong one cause it didn't work. My tach worked fine with the MP ignition. Easy fix, I installed a vintage Auto Meter and it works fine with the MSD. I think the adapter was $40-50 too. Here is a link to what the part looks like, you will need the right one.

http://www.ebay.com/itm/MSD-8910-Ta...Parts_Accessories&vxp=mtr&hash=item588c31e982
Click to expand...


i dont think he is running the box... just the coil...

if so yes the tach is fine with the coil...

what do you have the power lead hooked up to?? could be its the brake fuse and only getting power when you hit the brakes??
 
805moparkid said:
i dont think he is running the box... just the coil...

if so yes the tach is fine with the coil...

what do you have the power lead hooked up to?? could be its the brake fuse and only getting power when you hit the brakes??
Click to expand...
yes its just the coil. it is one of those little red ones (it was on there when i got the car) my power lead is a 12v constant from my stereo but im not sure where (they) took the power from.i will have to check that
 
66340SEDAN said:
I ran into the same thing, had an old Sun tach and MSD, they don't work together. MSD makes a Tach Adapter, you wire this in and then your tach will work. I tried this but must have got the wrong one cause it didn't work. My tach worked fine with the MP ignition. Easy fix, I installed a vintage Auto Meter and it works fine with the MSD. I think the adapter was $40-50 too. Here is a link to what the part looks like, you will need the right one.

http://www.ebay.com/itm/MSD-8910-Ta...Parts_Accessories&vxp=mtr&hash=item588c31e982
Click to expand...
sounds like i may need an auto meter.by the way would running just the coil cause a problem like this?
 
The question is, "what are you running for an ignition box?"


In a previous life, when I owned my sixpack RR, I could NOT get a Supertach to work reliably on (back then) CD ignition. They claimed "it would", I claimed "it wouldn't."
 
67Dart273 said:
The question is, "what are you running for an ignition box?"


In a previous life, when I owned my sixpack RR, I could NOT get a Supertach to work reliably on (back then) CD ignition. They claimed "it would", I claimed "it wouldn't."
Click to expand...

if you read it he is just running the coil... not the MSD box...
 
67Dart273 said:
OK is he running POINTS or a Mopar ECU or whut???
Click to expand...

wouldn't matter... non of them are CD's and can mess with the tach...

the tach would still use negitive side on the coil for the pickup...


OP:
try hooking up the light wire to the "hot wire" and cleaning the ground really well...

if nothing try on another vehicle... probably a bad tach if it is still not working....
 
im using the factory electronic ignition box and all its components with the exception of the coil. i had the tach in my charger and it worked fine. idk what to think.the chargers ignition is all mopar performance EI and a factory coil. i might have get another tach. strange. ive used a bunch of em but never ran into this before.i should try the stock coil and see if its works.i will try a new hot and ground and tie the light wire with my hot and see if that works.thank you guys for the help
 
73AbodEE said:
im using the factory electronic ignition box and all its components with the exception of the coil. i had the tach in my charger and it worked fine. idk what to think.the chargers ignition is all mopar performance EI and a factory coil. i might have to another tach. strange. ive used a bunch of em but never ran into this before
Click to expand...

well try another ground and make sure your connections are good...
 
805moparkid said:
well try another ground and make sure your connections are good...
Click to expand...
ok check this dumb crap out. i checked my ground and hot. i left every wire alone including the wire for the light because it couldnt get any better.and just for ***** and giggles , i took the green wire off of the NEGATIVE side of the coil and stuck it on the POSITIVE side of the coil and guess what,it WORKS. wtf ? is it possible to wire an MSD blaster coil backwards? the wiring is exactly how i bought the car and the wires have never been off the coil since ive had it. crazy. maybe thats how the coil works IDK.the car runs excellent and my tach is working the way it should.wierd
 
yes, it is possible to wire the coil backwards... it is not a good idea, but it will run for a while like that. I would be checking your wiring as it sounds like the + and - are switched.
 
I would make sure the coil is wired correctly. The + side of the coil should go to the ballast and bypass starting circuit, the neg should go with only one wire to the ECU If there is a radio capacitor, / condenser on the coil, it should be hooked to the pos side of the coil
 
o damn ok . i didnt think it would run wired backwards.the meathead i got the car from was having spark issues with the 225 in it,and i have since dropped a small block in it.will the backwards coil wiring damage other components or fry the coil? i am going out to fix that right now...
 
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