Honda Car Forum

Intermittently the tach on my CRX reads twice or double the actual
rpm. Its an HF and the idiot upshift light still lights at the
appropriate shift points, and the car seems to run normal.

The signal seems to be coming from the igniter (in the distributor)
which is firing the coil and thence plugs. Since it is a 4 cylinder,
4-cycle engine still (haven't riced it yet) this signal needs to be
divided by two to get rpm. I figure the divider circuit (a
flip-flop?) in the tachometer is faulty, not dividing by two, and thus
reads twice the rpms.

May be correlated with humidity. When its faulty, its faulty all day.
Rarely, the tach is real flaky and jerks between normal and double
readout several times a second.

Any electronics buffs know how a divider fails that way? Anyone
experienced this, had the tach out, and fixed it?

Guess I can live with it. Maybe its a feature: impress the passengers
by revving it up WAAYYY past the redline. If only it weren't
intermittent.

"bootch" <bootch@nc.rr.com> wrote in message
news:73b4503.0408191320.83a8739@posting.google.com ...
> Intermittently the tach on my CRX reads twice or double the actual
> rpm. Its an HF and the idiot upshift light still lights at the
> appropriate shift points, and the car seems to run normal.
>
> The signal seems to be coming from the igniter (in the distributor)
> which is firing the coil and thence plugs. Since it is a 4 cylinder,
> 4-cycle engine still (haven't riced it yet) this signal needs to be
> divided by two to get rpm. I figure the divider circuit (a
> flip-flop?) in the tachometer is faulty, not dividing by two, and thus
> reads twice the rpms.
>
> May be correlated with humidity. When its faulty, its faulty all day.
> Rarely, the tach is real flaky and jerks between normal and double
> readout several times a second.
>
> Any electronics buffs know how a divider fails that way? Anyone
> experienced this, had the tach out, and fixed it?
>
> Guess I can live with it. Maybe its a feature: impress the passengers
> by revving it up WAAYYY past the redline. If only it weren't
> intermittent.

It would be worth checking inside the distributor to see that all
four of the connectors on to the Igniter are properly pushed home
particularly the blue wire to the side connection which is the
tacho signal.


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