jumping Tachometer ??

[D111]

Started the Car to a loud screeching sound That went away for the most part after about a minute but then there was a consistent wine coming from the alternator long story short after removing the alternator and having It Checked out turned out most likely just to be a loose belt.

But my residual problem now is a jumping Tachometer, when I put my blinker on the Tachometer will jump all over the place,or if I turn anything electrical on for that Matter wiper blades etc. The Tachometer is Now hypersensitive.

Any thoughts?

[Ron61]

I am guessing that your tach is electronic. Since you removed the Alternator, I would check all grounds to be sure that one of them isn't loose or dirty. Also even though you had the Alternator checked out, it could still have a bad diode in it that would cause problems once you put any load on it. I have had a loose belt before on some cars and normally the screeching doesn't go away after a minute or so but will happen every time you get on it. How easy does the Alternator turn when it is cold and you turn the pulley with your hand?

Ron

[BAsque1]

Originally Posted by Ron61

I am guessing that your tach is electronic. Since you removed the Alternator, I would check all grounds to be sure that one of them isn't loose or dirty. Also even though you had the Alternator checked out, it could still have a bad diode in it that would cause problems once you put any load on it. I have had a loose belt before on some cars and normally the screeching doesn't go away after a minute or so but will happen every time you get on it. How easy does the Alternator turn when it is cold and you turn the pulley with your hand?

Ron

I agree with Ron, last year my alternator literally died in the middle of a nice run in Lake George. The tach was the 1st give away for it went ballistic on me. After I purchased a new alt the tach had apparently damaged and I ended up buying a new one. These electronic gauges are extremely sensitive to power surges and are easily damaged.
The other check up points are very valid and must be verified especially ground wires.
Good luck
Lou

[CowtownCobra]

Do not believe auto parts stores alternator testing machines. Replace your alternator.

[D111]

thank you very much I definitely agree,, it's a roush 342 the alternator is a Power Master Chrome ,but does not have any model number on it would anyone know where's the best source for me to get one and what model it might be ?

[D111]

what about having it rebuilt does that usually work out okay?

[cbreez]

Has it jumped out of the car yet??? or is just the needle bouncing around within the tach?

[BAsque1]

Originally Posted by D111

thank you very much I definitely agree,, it's a roush 342 the alternator is a Power Master Chrome ,but does not have any model number on it would anyone know where's the best source for me to get one and what model it might be ?

Tuff-Stuff Ford High Output Custom Billet Alternator

[jhv48]

Where is the needle on your ammeter pointing when all this is happening?

[D111]

ended up bringing it to a highly recommended alternator shop just spoke with the gentleman he has finished it ,he said the rectifier was shorted out ,while he was in it he replace the bearings and brushes I'll pick it up tomorrow and see how it goes

.I'm also going to add an additional ground from the battery to the chassis I was going to add an additional motor ground to the chassis but realized my engine has solid metal motor mounts so I think that would be definitely redundant.

[D111]

Originally Posted by jhv48

Where is the needle on your ammeter pointing when all this is happening?

the amp meter was reading anywhere from 11 to 14 amps needle would jump whenever an additional Electric burden was put on it engine fan or even a blinker needle bounced up to 4000 rpm then right back.

[427 ISH]

Had the same issue with a Speed Hut tach. I needed to instal an inline noise reducer to protect the sending unit from stray current. If the Alternator repair does not fix the tach issue, call the gauge manufacturer. May be a known issue.

[cbreez]

Okay since you have no humor ...these cars are so simple.

Powermaster's are excellent products, doubt anything was wrong with it. A bad bearing will make noise for a long time before it seizes. A loose belt won't ruin a bearing, a tight one would.

Why would you think a ground is the problem if it worked fine for a long time?

Where does your tach signal come from? Your MSD box? hmmm...

[Cashburn]

Probably loose posts inside battery shutoff box. Solid mounts are aluminum, look that up.

[D111]

it appears that the problem is solved installed the rebuilt alternator did nothing else and there is no dancing of the tachometer any longer
. he gave me all the old parts with the rebuilt alternator.

[D111]

Originally Posted by Cashburn

Probably loose posts inside battery shutoff box. Solid mounts are aluminum, look that up.

Thank You Jay, I was just thinking that it was redundant for me to put an additional motor ground to the chassis if the motor mounts are metal aluminum I thought that would be a natural ground for the whole motor already vs rubber motor mounts

over the years I put hyper ground systems on most of my cars just to have a secure grounding system seems to help sometimes and I don't think you could have too much ground but certainly too little.

[D111]

Originally Posted by Cashburn

Probably loose posts inside battery shutoff box. .

just checked my connections this morning loose as a goose thanks again J