Combo Gauge Problems

356 Porsche-related discussions and questions.
Message
Author
david pettengell
356 Fan
Posts: 205
Joined: Fri Jul 18, 2014 2:18 am

Combo Gauge Problems

#1 Post by david pettengell » Tue May 28, 2019 3:56 pm

So, my combo gauge was not working for the oil temp and gas level so I took it out and found a black wire which goes to earth out of its bullet connector. I pushed it back in and both needs starting jumping so at least something is happening.

The problem is that all they are doing is jumping back and forth and not showing any real levels. It looks like the fuel gauge already has one of the standard "regulators" to stop the fluttering of the gas level.

So I followed the instructions on here to test both senders and they seem fine (got resistance 46 ohms back for the fuel sender for example).

So I am assuming my gauge is screwed? Could it be anything else?

If my gauge is screwed are there any good 6v repro units? or is it a case of sending off to one of the California gauge guys (NH Speedometer or Palo Alto Speedo?)

Also, has anyone tried the LED bulb kits for gauges as my bulbs are almost invisible in daylight?

Thanks for any advice!

User avatar
Jim Clement
356 Fan
Posts: 459
Joined: Tue Oct 26, 2010 10:46 am
Tag: 1957 356 A Coupe
Location: Calgary Alberta

Re: Combo Gauge Problems

#2 Post by Jim Clement » Tue May 28, 2019 5:33 pm

I think the ground wire should be brown ??..
combo gage 2.PNG
combo gage 2.PNG (831.42 KiB) Viewed 666 times
Attachments
combo gage.PNG
combo gage.PNG (660.39 KiB) Viewed 666 times
 

david pettengell
356 Fan
Posts: 205
Joined: Fri Jul 18, 2014 2:18 am

Re: Combo Gauge Problems

#3 Post by david pettengell » Wed May 29, 2019 10:25 am

I thought so too but mine is black?

User avatar
Doug McDonnell
356 Fan
Posts: 3838
Joined: Sat Apr 05, 2008 8:21 am
Location: Augusta,Michigan

Re: Combo Gauge Problems

#4 Post by Doug McDonnell » Wed May 29, 2019 10:57 am

Good pictures of a C Combo gauge wiring here: viewtopic.php?f=1&t=27048
1965 356C There is never enough time to do it right, but always enough time to do it over.

david pettengell
356 Fan
Posts: 205
Joined: Fri Jul 18, 2014 2:18 am

Re: Combo Gauge Problems

#5 Post by david pettengell » Fri May 31, 2019 1:40 pm

Anyone got pictures of a "B" gauge wiring? I am confused!

User avatar
Jim Clement
356 Fan
Posts: 459
Joined: Tue Oct 26, 2010 10:46 am
Tag: 1957 356 A Coupe
Location: Calgary Alberta

Re: Combo Gauge Problems

#6 Post by Jim Clement » Fri May 31, 2019 2:44 pm

In both my case and in the attached picture, the ground wire i think is a ring type connected to a stud off of the back of the gauge, Should be brown.
Attachments
brown to ground.PNG
brown to ground.PNG (523.74 KiB) Viewed 542 times
 

User avatar
Doug McDonnell
356 Fan
Posts: 3838
Joined: Sat Apr 05, 2008 8:21 am
Location: Augusta,Michigan

Re: Combo Gauge Problems

#7 Post by Doug McDonnell » Fri May 31, 2019 2:45 pm

+1 on brown ground to stud on case.
1965 356C There is never enough time to do it right, but always enough time to do it over.

User avatar
Mike Wilson
356 Fan
Posts: 4826
Joined: Tue Apr 15, 2008 4:37 pm
Location: SW Los Angeles

Re: Combo Gauge Problems

#8 Post by Mike Wilson » Fri May 31, 2019 3:50 pm

I have the LED bulbs. Very bright.

Mike
Mike Wilson
Lomita, CA
'63 B coupe

User avatar
Al Zim
356 Fan
Posts: 1856
Joined: Fri Mar 14, 2008 9:14 pm
Location: FT.WORTH/DALLAS TEXAS

Re: Combo Gauge Problems

#9 Post by Al Zim » Fri May 31, 2019 8:29 pm

The combo gauge is grounded by the brown wires all porsche's of that era used brown grounds and by the bracket that holds the gauge to the dashboard. Clean the tips of the bracket with a piece of sandpaper and the spot they touch the same way. The fuel gauge (especially on the 61 and earlier cars) tended to wiggle around as the float bounced in the partially filled gas tank. Long ago our electrical grue developed a device to calm this gauge down. The temperature gauge wiggling is probably due to the wires at the sending unit fraying. give the wire a slight tug and it will break. Put on a new end and your situation should be solved. Moving air in the engine compartment was wiggling the wire. al zim
 

User avatar
Greg Bryan
356Talk Moderator
Posts: 2288
Joined: Sat Oct 04, 2008 1:05 pm
Tag: Be Nice!
Location: San Pedro, CA 90732

Re: Combo Gauge Problems

#10 Post by Greg Bryan » Sat Jun 01, 2019 2:16 pm

Jim Clement wrote:
Fri May 31, 2019 2:44 pm
In both my case and in the attached picture, the ground wire i think is a ring type connected to a stud off of the back of the gauge, Should be brown.
In this case, the grounds are attached to female bullet receptacles that are attached as shown in the picture. The brown wire has bullets attached to them and push into the receptacles.
This is a C combo gauge - earlier cars may have the ground attached to the thumb screw posts as stated above.
Porsche kept adding more and more grounds in the harness as the years went by to improve the reliability of the electrical system.
Greg Bryan
356Talk Moderator

User avatar
Greg Bryan
356Talk Moderator
Posts: 2288
Joined: Sat Oct 04, 2008 1:05 pm
Tag: Be Nice!
Location: San Pedro, CA 90732

Re: Combo Gauge Problems

#11 Post by Greg Bryan » Sat Jun 01, 2019 2:24 pm

By the way, be very careful removing the bullets from the gauge receptacles - those black risers you see above - as they will snap off in a heartbeat. You kind of have to tease the bullets out … A bit of WD40 and firm grip with needle nose and pull straight out - no angled or side pulling on the wires.
Greg Bryan
356Talk Moderator

david pettengell
356 Fan
Posts: 205
Joined: Fri Jul 18, 2014 2:18 am

Re: Combo Gauge Problems

#12 Post by david pettengell » Sat Jun 01, 2019 3:49 pm

Thanks all, will double check the colour of the ground wire on mine. I will check all the connections as well to see if that helps with the needles jumping

User avatar
Mervyn Hyde
356 Fan
Posts: 789
Joined: Wed Nov 25, 2015 9:12 pm
Location: Sunshine Coast Australia

Re: Combo Gauge Problems

#13 Post by Mervyn Hyde » Sat Jun 01, 2019 4:22 pm

Mike Wilson wrote:
Fri May 31, 2019 3:50 pm
I have the LED bulbs. Very bright.

Mike
Same got some LEDs and now I can see! No impact on the gauges. Your problem sounds electrical connections (dirty connectors, a wrong connection, faulty earth, or incorrect power-in source) and not related to the gauges per se. On the fuel gauge sender (at the tank) I added, across the sender terminals, an ultra cheap capacitor (0.1 Farad) and it smoothed the operation out, damping transients. Not sure what 'regulator' (?) you have there.

I found this helpful
Image
Merv
TYP356
1963 356B T6
1968 911 SWB

User avatar
Mervyn Hyde
356 Fan
Posts: 789
Joined: Wed Nov 25, 2015 9:12 pm
Location: Sunshine Coast Australia

Re: Combo Gauge Problems

#14 Post by Mervyn Hyde » Mon Jun 03, 2019 6:51 pm

How did you go David?
Merv
TYP356
1963 356B T6
1968 911 SWB

User avatar
Mike Smith
356 Fan
Posts: 917
Joined: Wed Mar 26, 2008 10:55 am
Tag: Its Only for Fun
Location: UK
Contact:

Re: Combo Gauge Problems

#15 Post by Mike Smith » Wed Jun 05, 2019 4:01 am

Post
by Greg Bryan » Sat Jun 01, 2019 2:24 pm
By the way, be very careful removing the bullets from the gauge receptacles - those black risers you see above - as they will snap off in a heartbeat. You kind of have to tease the bullets out … A bit of WD40 and firm grip with needle nose and pull straight out - no angled or side pulling on the wires.
PLUS 1 on that Greg
Mike Smith (Essex - UK)

Post Reply