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Old 02-14-2019, 03:43 PM   #1
sap727
Scooby Newbie
 
Member#: 12320
Join Date: Nov 2001
Location: Rockwall, TX
Vehicle:
2015 Crosstrek
White

Default Speedometer and odometer with AC and reverse lights

I purchased a 2005 Saab 92x Aero thinking it would be a fun car, but it has been an electrical nightmare. The previous owner made so many bad choices with the wiring I've spent days trying to fix it.

What I am dealing with now is the reverse lights not coming. I suspect the back-up switch sensor is bad. I am going to check that tomorrow on a lift.

Here is the one I cannot figure out. When the A/C first kicks on, the speedometer and odometer stop working. Sometimes they will start working again when the A/C runs for a bit, but it always happens when the compressor first kicks on. If anyone has seen this before, what was the fix?

Thanks!
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Old 02-17-2019, 11:51 AM   #2
Cougar4
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Member#: 53443
Join Date: Jan 2004
Location: Anchorage, AK
Vehicle:
2001 LL Bean Outback
Winestone

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I suspect there is a bad ground to those items you stated quit working. When the AC is turned on, the higher current required by it causes a larger voltage drop across the bad ground connection and that kills the other devices. Not enough voltage gets to them due to the series voltage drop across the bad ground connection. When the bad connection is fixed then all the voltage will appears across the loads and they will work like they should. To prove that is the problem use a jumper wire and connect one end to the ground going to the dash and the other end directly to the negative (ground) side of the battery. If the gauges then work you have proved that is the cause of the problem. If the ground isn't the problem then verify that proper voltage is getting to the gauges while the problem is occurring. The problem may be on the supply side of the circuit instead of the ground side.
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Old 02-18-2019, 08:06 AM   #3
sap727
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Member#: 12320
Join Date: Nov 2001
Location: Rockwall, TX
Vehicle:
2015 Crosstrek
White

Default

Thanks for all the info! I'll definitely give this a shot.

Quote:
Originally Posted by Cougar4 View Post
I suspect there is a bad ground to those items you stated quit working. When the AC is turned on, the higher current required by it causes a larger voltage drop across the bad ground connection and that kills the other devices. Not enough voltage gets to them due to the series voltage drop across the bad ground connection. When the bad connection is fixed then all the voltage will appears across the loads and they will work like they should. To prove that is the problem use a jumper wire and connect one end to the ground going to the dash and the other end directly to the negative (ground) side of the battery. If the gauges then work you have proved that is the cause of the problem. If the ground isn't the problem then verify that proper voltage is getting to the gauges while the problem is occurring. The problem may be on the supply side of the circuit instead of the ground side.
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