Tach jumps when turning key from "on" position

[butters]

I just got my cluster back from an SI rebuild and complete checkup, plugged it in and turned the key to test and found everything working just fine. However, upon turning the key away from the "on" position - to accessory or to off, either way - the tachometer needle went from 0 to about idle speed, say 800 rpm, after a couple of seconds and stayed there.

So I pulled the connectors and the coding plug, then re-connected it all and tried again. There are no obvious wire issues behind the cluster. On this second attempt, after turning from "on" the tach goes to 0 then will hiccup towards idle rpm after a couple seconds before coming to rest on the 0 peg.

Can anyone offer insight or experience with this? Some google results pointed to the coding plug but mine seems fine and I hadn't had any problems with it before the SI work. What could possibly be triggering this seemingly consistent signal to be pulsing into the tach after shutdown? I'm going to bed and will have to fiddle with it after work tomorrow..

[E30NJ]

Did you check that everything is properly grounded? My guess would be that there is a ground somewhere thats making it jump like that.

[butters]

Did you check that everything is properly grounded? My guess would be that there is a ground somewhere thats making it jump like that.

Agree, there must be some signal interference coming in somewhere. I'll have to look up the wiring to see what sends that tach signal.

[jdt10768]

mine blips the second I turn it OFF, just jumps a bit. I thought that was normal, but not sure. When I get around to replacing my odo gears, I will make sure all connections are tight and clean / corrosion free

[butters]

mine blips the second I turn it OFF, just jumps a bit. I thought that was normal, but not sure. When I get around to replacing my odo gears, I will make sure all connections are tight and clean / corrosion free

I've read several threads on various forums, and it a few people have called it normal. Mine does that same blip now. I will probably take a drive and verify that it all functions normally otherwise, but of course it would be preferable to figure this out before completely buttoning up the cluster. The process of R&R from the dash sucks, it's never easy and I always worry about breaking the lens (which I've already done before).

[butters]

False alarm. I think it may have something to do with the car sitting on a battery tender for a month while the cluster was out. 24 hours later I'm not seeing any tach oddities, everything is A-ok.

[eurolife]

Mine has a small blip as well, figured it was normal as everything still functions as it should

[Quinthirty]

Interested to see how this blip can be fixed.

[ELVA164]

I've always noticed that happening with a weak battery. Maybe a bad/worn voltage regulator for those who experience it? I have a feeling the battery OP's issues went away after the alternator got some charge into the battery; is that the case OP?

[butters]

I've always noticed that happening with a weak battery. Maybe a bad/worn voltage regulator for those who experience it? I have a feeling the battery OP's issues went away after the alternator got some charge into the battery; is that the case OP?

I was also going to suggest voltage regulator or related issues as a culprit. My symptoms went away once the battery was regulated as usual by the car. Initially after putting my cluster back in, it was still on a battery tender from sitting for a month. I almost wonder if the voltage was too high, though the tender does trickle and automatically regulate so as not to reduce lifespan.