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'86 coupe digital dash problem

2343 Views 7 Replies 4 Participants Last post by  Ukonjack
My battery went dead on my '86 coupe. After jump starting it, I noticed the digial volt readout was 9.9v, the coolant temp was 172deg, the oil pressure was 72lbs, and the oil temp was 125 degrees. I charged the battery to 13.2v (using a battery charger), the car starts and runs great, but these digital readouts haven't changed. All the other readouts seem to be normal---tach, speedometer and gas gauge all work, as well as the average & instantaneous mileage. Also, when I change the readout from volts to coolant temperature, the readout changes then immediately goes back to 9.9v.

any ideas what might be causing the problem??

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black85vette: took your advice. pulled the cables, cleaned them, put them back on. Now the voltage readout changed from 9.9v to 9.8v. The battery is actually reading 12.8v using a VOM.
Mine is a little different than yours. I checked my alternator output and it was 14+v. I also fully charged the battery and the digital readout stayed a 9.9v.

Whats strange is that, today, I pulled the negative lead off the battery and left it off for about 4 hours, hoping that the computer would reset itself. When I reconnected the negative, the digital readout increased to 18.4v. Since its still out of range, I continue to get to 175degree coolant temperature reading.
Bad ground somewhere. I had similar trouble and replaced the negative battery cable and the trouble went away.
I'm starting to lean towards a bad ground. If you read my previous post, I'm now seeing 18.4v after removing the negative lead from the battery for 4 hours.

Do you think a bad ground would also effect the readings for oil pressure/oil temperature? Both of these remain as constant readouts also.
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