Tach gauge keeps dieing for a couple seconds and coming back...?

[geck0]

As the title says outta the clear blue my tach needle drops to 0 (it runs perfectly fine) then after a little bit it comes right back up. bumps kinda seem to effect it but reached in a jiggled wires under dash and in engine bay does nothing... any ideas?

 

[adsm08]

Bad connection somewhere. The head may be dying, smack the top of the dash.

 

[geck0]

smacked the dash nothing... and i've jiggled wires both in and out nothing

 

[geck0]

its definetly getting worse. when you refer to "head" i assume you mean the actual tach?

 

[geck0]

OK so some new info.. it only seems to do it after the truck is heated up. in turn it makes me lean towards the ignition control module. Does this hold any water or am I just guessing...lol

 

[unoleisu]

Funny that I can't seem to find the tach in my Bii electrical trouble shooting manual.... It does show a DG/Y wire going from the coil to the instrument cluster.....and spliced to go to the TFI, and also thru a resistor to the ECA.

Any way, the tach usually recieves voltage pulses from the ignition system, usually connected to the coil. a circuit in the tach converts the ignition pulse signals into a varying voltage which is applied to a voltmeter that indicates the engine speed.

That being said, I'd start checking connections between the two. I personally clean and use "bulb grease" on every individual connection that I inspect, just in case, even if it looks good. These trucks are 20 something years old. I like to pull every pin and socket out of the connectors, one at a time and clean them thouroghly, so I don't have to come back to it any time soon.

Don't forget the grounds. Make a new metal to metal contact (sand them with fine sand paper and use bulb grease, use a wire brush on screw threads), to insure future dependability.
Good luck, and go get'em!

 

[geck0]

the other night I went through and pull the dash apart a bit and messed with the few grounds I saw loosening and torquing them again. (no luck) however i've had the tach needle SPIKE all the way to redline now twice then kick back to normal activity. I work in a parts store/ machineshop so I just picked up a new magnetic pick up coil (pretty sure it was magnetic not the hal effect) and a new ignition control module pulled the disty pulled it apart cleaned and replaced those parts. Seems to do ok so far about a 5 mile drive truck got to operating temp and no tach issues...FINGERS CROSSED tomorrow on the way home from work will be the test thats when it seems to happen alot.

 

[geck0]

BTWUNOL thanks for the info that will be the next course of action

 

[geck0]

the other night I went through and pull the dash apart a bit and messed with the few grounds I saw loosening and torquing them again. (no luck) however i've had the tach needle SPIKE all the way to redline now twice then kick back to normal activity. I work in a parts store/ machineshop so I just picked up a new magnetic pick up coil (pretty sure it was magnetic not the hal effect) and a new ignition control module pulled the disty pulled it apart cleaned and replaced those parts. Seems to do ok so far about a 5 mile drive truck got to operating temp and no tach issues...FINGERS CROSSED tomorrow on the way home from work will be the test thats when it seems to happen alot.

WOW MY PUNCTUATION IS HORRIBLE..

 

[geck0]

no luck did it before i got out of the lot from work to go home... heat related and not the disty

 

[geck0]

could the tach act up from the sprout or pill thing? I re adjusted the disty and i've gotten a whole day without it acting up.....so far

 

[kimcrwbr1]

Probably just a loose connection or wire intermittent faults are always the hardest and you usually just stumble on it. Just wiggleing the wire could have been the problem. There is a wiggle test you can use for this. Do the KOEO or KOER test and after it sends you the codes and stops flashing stop the test then restart by disconnecting the jumper or switching the reader off then connect the jumper back up. this is the wiggle test and go around and wiggle and tap on all the connectors and sensors. If it sees a fault it will give you a flash beep however you are getting the codes with a one and it will put that code in memory. The beeper works good you dont have to watch the light you can hear when you discover a problem. It will be close to where your hans are at that time. GL

 

[geck0]

its bugging me now started back up again ... grrr i hate this hunting problems crap

 

[geck0]

so get this. i must of either had spark plug wire for cyl 1 too close to some wire on the passenger side. After moving my wiring harness back up to the hook bracket on the back of the intake. All the sudden now the tach works fine.... i love non known fixes!