Tach not working and voltage meter spikes to 18V

turboman1

turboman1

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Aug 20, 2008
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Well, my tach has stopped working and the voltmeter will jump to 18V at any time you touch the gas. At idle the tach doesn't work but the voltmeter reads 12-14v.

1) Is there a fuse for the tach i could check that if blown would send the wrong signal to the alternator for charge?

2) Is there a voltage regulators external to the alternator that needs to be replaced?

3) Any other ideas?

To make a long story short my transmission has not been shifting right and I think that tach not working and the alternator spiking has been sending bad signals to the transmission causing its problem. What do I need to start checking for?

Thanks
Adam
 
try unhooking the crank sensor and starting the truck, in the front the connector is toward the top have seen these short and cause alot of electrical issues
 
yes it is either disrupted crank sensor signal, or bad crank sensor...
 
Would that cause the volt meter to spike at anything greater than an idle?

So i should disconnect the crank sensor and see if the volt meter spikes again?

Adam
 
yes to both questions... tach signal controls the voltage regulator in the PCM.. hopefully the PCM isn't fried..
 
Alright thanks Ill give this stuff a try and see what I can come up with

Thanks
Adam
 
Quick Question: Where could I possible get a tach/crank sensor pickup from because the local dodge dealer wants $213 w/o tax :(.

Adam
 
turboman1 said:
Well, my tach has stopped working and the voltmeter will jump to 18V at any time you touch the gas. At idle the tach doesn't work but the voltmeter reads 12-14v.

1) Is there a fuse for the tach i could check that if blown would send the wrong signal to the alternator for charge?

2) Is there a voltage regulators external to the alternator that needs to be replaced?

3) Any other ideas?

To make a long story short my transmission has not been shifting right and I think that tach not working and the alternator spiking has been sending bad signals to the transmission causing its problem. What do I need to start checking for?

Thanks
Adam
Click to expand...

I think its ECU.


My friend had similar problems: at first start charging problem, next was tranny problems with tach malfunction, he just replace the ECU and no more problems.


The alternator voltage regulator is inside of the ECU and also ECU will send out 5V for tranny and tach .
 
Is there anyway to check the pcm because it is 500$ for another one?

Thanks
Adam
 
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