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JK McDonald's Avatar
 
Join Date: Oct 2003
Location: Texas
Posts: 811
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Voltage Filter Capacitor -

We just returned from a loop down through the East Texas Hill Country and Miss Purdy was running great. The only thing I did notice on the trip was that the Temp, Fuel, Oil Pressure and Volt Meter gauge needles have deveoped a slight flutter at times. Has anyone seen this before ? Is there a instrument panel voltage filter capacitor somewhere that may be going bad ? It seems to be most noticeable after being on the road a while.

Thanks, Michael
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1984 928S - "Miss Purdy"
1987 911SC - "Frau Helga"
1986 930 - "Well Hung"
Old 11-17-2017, 10:57 AM
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Quote:
Originally Posted by JK McDonald View Post
We just returned from a loop down through the East Texas Hill Country and Miss Purdy was running great. The only thing I did notice on the trip was that the Temp, Fuel, Oil Pressure and Volt Meter gauge needles have deveoped a slight flutter at times. Has anyone seen this before ? Is there a instrument panel voltage filter capacitor somewhere that may be going bad ? It seems to be most noticeable after being on the road a while.

Thanks, Michael
I rather doubt there is a filter capacitor for that. It sounds like more of a bad connection. I have noticed my volt meter does a little dip at times but not the rest of the gauges. Probably the best way to check would be to place a volt meter right on the battery. The only other thing I can think of is your voltage regulator acting up. The battery itself acts as a big capacitor. These cars have many connectors and circuit boards and with time get corroded, most not being gold plated. Lots of time has passed since production!
__________________
1986 928S
32 valve engine
All stock, automatic, 539 Weissgold Metallic, 70K original miles, Hankook Ventus 2 tires.
Previously owned: 67 Vette, 427 L88 Stingray, 74 De Tomaso Pantera L
Old 11-17-2017, 11:37 AM
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Instrument POD Connections -

Hey Harborman, you're right about the 928 having a $hit load of geriatric electrical contacts, connections and connectors behind the instrument panel. I had removed and cleaned up mine not long ago while trying to sort out why there was a difference (about 1.5 volts) between the jumper post and the dash voltmeter reading. For some peace of mind, I finally installed a separate digital voltmeter to accurately monitor the output of my Delco CS130 Alternator. I'll take your suggestion and recheck all the POD connections again.

Some automotive instrument panels have a Zener Diode/voltage regulator or filter circuit added to help keep all the readings stable during hot/cold/high RPM/electrical load fluctuations/etc... situations. I just didn't know if the 928 had a similar circuit.

Has anyone else noticed any instrument flutter ?
Thanks, Michael
__________________
1984 928S - "Miss Purdy"
1987 911SC - "Frau Helga"
1986 930 - "Well Hung"
Old 11-17-2017, 04:25 PM
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Quote:
Originally Posted by JK McDonald View Post
Hey Harborman, you're right about the 928 having a $hit load of geriatric electrical contacts, connections and connectors behind the instrument panel. I had removed and cleaned up mine not long ago while trying to sort out why there was a difference (about 1.5 volts) between the jumper post and the dash voltmeter reading. For some peace of mind, I finally installed a separate digital voltmeter to accurately monitor the output of my Delco CS130 Alternator. I'll take your suggestion and recheck all the POD connections again.

Some automotive instrument panels have a Zener Diode/voltage regulator or filter circuit added to help keep all the readings stable during hot/cold/high RPM/electrical load fluctuations/etc... situations. I just didn't know if the 928 had a similar circuit.

Has anyone else noticed any instrument flutter ?
Thanks, Michael
Also clean those ground points. There are a number of them under the Pod as I recall.
__________________
1986 928S
32 valve engine
All stock, automatic, 539 Weissgold Metallic, 70K original miles, Hankook Ventus 2 tires.
Previously owned: 67 Vette, 427 L88 Stingray, 74 De Tomaso Pantera L
Old 11-18-2017, 05:57 AM
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Gauge Needle Flutter -

Hey Harborman - You were right about cleaning the ground points again. Once I pulled the instrument pod I also cleaned all the edge connectors with alcohol and a soft eraser. Then I slightly tighten each nut on the back of the Volt Meter, Oil Press, Tach, Fuel and Temp gauge connections. I didn't find any Gauge B+ power filter (cap, zener, etc...) components and the schematic doesn't indicate they were used.

Just for good measure - I soldered the 3 crimped copper rivets in the center of the flexible ribbon that brings in the B+, Grd and Pulse Signal to the Speedometer.

Not sure which step actually fixed the slight needle flutter on the gauges but everything is now better than new.

Thanks for your help - Michael
__________________
1984 928S - "Miss Purdy"
1987 911SC - "Frau Helga"
1986 930 - "Well Hung"
Old 11-27-2017, 07:23 PM
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Quote:
Originally Posted by JK McDonald View Post
Hey Harborman - You were right about cleaning the ground points again. Once I pulled the instrument pod I also cleaned all the edge connectors with alcohol and a soft eraser. Then I slightly tighten each nut on the back of the Volt Meter, Oil Press, Tach, Fuel and Temp gauge connections. I didn't find any Gauge B+ power filter (cap, zener, etc...) components and the schematic doesn't indicate they were used.

Just for good measure - I soldered the 3 crimped copper rivets in the center of the flexible ribbon that brings in the B+, Grd and Pulse Signal to the Speedometer.

Not sure which step actually fixed the slight needle flutter on the gauges but everything is now better than new.

Thanks for your help - Michael
Glad to see all is working now. To clean connectors I use CRC Electronic Cleaner or Deoxit, both work well.
__________________
1986 928S
32 valve engine
All stock, automatic, 539 Weissgold Metallic, 70K original miles, Hankook Ventus 2 tires.
Previously owned: 67 Vette, 427 L88 Stingray, 74 De Tomaso Pantera L
Old 11-28-2017, 05:04 AM
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