Tachometer screwy

[wolf39us]

haha so I found out something interesting, ok so my tachometer in my 87 V8 GT ...USED to work...

however now what it does is when I'm at about 3k it will suddenly jump from 1k to 3.5 or so and keep going lol

however I noticed something that might be a clue as to the problem

when I start the car the needle will force it self downwards (meaning away from the numbers)

also when the car is on....if I open a window in any direction....the needle will force it self downwards as well

now I did electrical for awhile....but I have no clue as to the circuit going on back there...would this be a grounding problem or a possible short??

I can't really tell

oh if it helps any... my fuel gauge is always full?? until I have like no gas left and then it's suddenly almost empty (but my gas light still works thank god lol)

 

[TrickFlowd]

I had this problem and it was caused by the battery almost dead. (winter weather) I started the car, which it barely started(*18 degrees timing in 20 degree weather), and my tach did this. I put the battery on a charger for a full day. And it hasn't done it since. Could possibly be a ground problem also. I did retighten my cables at the battery aswell.

 

[Nova]

pick up a ford EVTM manual on ebay!

 

[wolf39us]

well this happens in normal weather too...so I don't think it's the battery

oh hey anyone know...if when the battery gets so low that the starter just clicks ....at that point can you pop start it...or is there still not enough juice to kick it on?