Tach reading 1100 rpm with key off

C

cj5wagomando

NAXJA Forum User

Location

Livermore, CA

• Apr 21, 2010

• #1

1987 wagoneer limited 4.0 L Auto


(this is my daughters rig and I am trying to sort out a couple issues on it)

I just noticed this.......

With the key off the tach needle will not relax to zero....it hovers at about 1100rpm -it is getting power and may be a cause of a consistently weak battery.

Where would I look to try to figure why/where the Tach is experiencing constant power with key-off.

Any help would be appreciated, thanks

Dave.

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Apr 21, 2010

• #2

Tach is powered off the IP fuse. The 3-wire connector on the ICM connector "C" is the tach signal, it is reading off a ground for the tach signal.

You can also access the signal at the D1 diagnostic connector, pin 1.

Your tach may have simply failed. You can try disconnecting "C" at the ICM and see if it goes to zero.

 

C

cj5wagomando

NAXJA Forum User

Location

Livermore, CA

• Apr 21, 2010

• #3

Thanks Joe,

I had the whole 3-wire plug removed from the ICM at lunch a few minutes ago and the tach stayed around 11000. the tach seems to work just fine while the engine is running, but drops to zero when turned off and then goes up to 11000 within one second or so.

Dave

 

C

cj5wagomando

NAXJA Forum User

Location

Livermore, CA

• Apr 21, 2010

• #4

1100 not 11000:dunce:

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Apr 21, 2010

• #5

Curious. Some kind of dust bunny in the IP? Might pull it, clean it, see what happens.

 

C

cj5wagomando

NAXJA Forum User

Location

Livermore, CA

• Apr 21, 2010

• #6

I am trying to get all these abbreviations down, but IP is not comming to me..

Thanks,
Dave

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Apr 21, 2010

• #7

Sorry, instrument panel.

 

C

cj5wagomando

NAXJA Forum User

Location

Livermore, CA

• Apr 21, 2010

• #8

thanks again Joe,

I will let you know what I find .


Dave.

 

C

cj5wagomando

NAXJA Forum User

Location

Livermore, CA

• Apr 23, 2010

• #9

I did not pull the IP but did disconnect the batt and pulled fuses. It seems my Tach just wants to rest at 1100.

I am taking it on a bit of a trip for the weekend so pulling the IP is not in the cards, but maybe next week.

I appreciate the responses.

Dave.

 

G

gdavis

NAXJA Forum User

Location

Midwest

• Apr 24, 2010

• #10

Just wondering, - while the ignition is off, might try shorting the Green/White tach wire to ground and see if the tach drops (parks) at zero rpm. Sorry I don't know what pin that is.

If that doesn't cause it to drop to zero, wonder if the tach movement itself has become magnetized? I'll run a big speaker magnet past one of our older XJ's tach to see if it will pull it off of zero.

 

C

cj5wagomando

NAXJA Forum User

Location

Livermore, CA

• Apr 26, 2010

• #11

I can try grounding the wire.. Thanks, Dave.

 

Harlee&Tahoe

NAXJA Forum User

Location

South Lake Tahoe, CA

• Feb 13, 2011

• #12

It never shut off, just went into silent economy mode... :greensmok:repair:



Mine does this too;
Off: Needle relaxes
On: Needle jumps to 0
Run:Needle shows respective RPM

Now to figure out why mine recently started to stay at zero,
even while revving engine