Tach problems when raining

Ted Stringer · 07-23-2001, 07:45 AM

I am having problems with my tach reading correctly when it is/has recently rained. The roof has sealing problems and when it rains outside some gets inside. What happens is that the tach reads low. It lists the idle as 500 RPM instead of the usual 850. It doesn?t seem to effect engine operation. Also as the engine revs the tach will make it up to about 1000 when my ear (highly inaccurate) says 3000 - 3500. This problem seems to fade back to an accurate reading after about 3 - 4 miles, quicker with the defroster on.

I searched the previous posts and couldn?t find anything. I think that it is loose or corroded connector, but where does the tach feed from? The haynes manual isn?t clear about the ignition and instrumentation wiring. A schematic of this area would help a lot, and a list of where the connectors are in the car.

Thanks in advance.

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Ted Stringer
nuke3@juno.com
'84 911 Targa aka pocketrocket

Ted Stringer · 07-23-2001, 11:27 AM

Early_S_man, do you have one of those schematics for the tach circut on an '84?

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Ted Stringer
nuke3@juno.com
'84 911 Targa aka pocketrocket

Roland Kunz · 07-23-2001, 11:54 AM

Hello

The tach signal is generatet in the DME brain and I would look under the driving seat if the wireloom isnt drowned in water. The brain sits higher and will not see to much exept you brake to hard and it will spill from the rear into the unit.

Tach signal goes up to a 4 pin connector placed beside the filler neck and from that junction into the main wireloom.

Grüsse

Ted Stringer · 07-23-2001, 12:28 PM

Thanks Roland, now I know where to go digging tonight

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Ted Stringer
nuke3@juno.com
'84 911 Targa aka pocketrocket