Dimmer Knob Fix

[DRACO A5OG]

Issue:
Sorry no pics

Dimmer Knob was sloppy causing the gauges & knobs to flicker. Worse yet, a poor contact so it would cause the interior lighting not to be as bright as it should be.

Attempted to keep the dimmer on the always high position but due to the loose contact it would at times flicker. Not Good.

Solution:

Remove Slop or order a New Dimmer .

(Shameless Plug for Plug)

Tools Needed:

9 paper tags to label the wires and terminals (may need more for the later models)
2 Pin Tools
Needle Nose Plyers
Dremel with small grinding end
Di-electric Grease
Lube
Electrical Parts Spray
2 screw/nut set OD of rivets

The Fix:

Dis-assembly:

1. Safety 1st, Disconnect the Battery.

2. Remove Knob, if housing is loose, stop do not continue to turn, pull the knob out to it's max setting and use a pin too through the shaft it has a side access hole ( you will use this to align and tighten the knob on to the shaft ) then continue to remove or in a pinch hold the back of the housing by reaching behind the dash.

3. Using the pin tools, remove plastic retaining nut spin it off then by hand.

4. Gently and patiently, reach behind the dash and push the housing towards the front of the car then the exposed shaft down and out. It will pull out about 3-4 inches, enough room to pull the connectors and label them

5. Label them, mine took 9 labels but the dimmer had 2 more terminals not being used. So label them carefully.

6. Using the needle nose pull the connectors at the rubber covered connectors not the wire.

Dimmer Dis-assembly

7. Once removed, verify the dimmer is in fact the culprit ( loose ). You will see 3 rivets. You only need to remove the two side brass rivets using the Dremel. Do not tamper with the upper middle one. Grind on the metal side not the ceramic/plastic side. After the rivet lip is gone, use the pin tool to push the rivet through. Be gentle and push not slam at the rivet or you will damage the ceramic (ask me how I know)

8. The brass housing will now slip off.

9. Pull out the internal shaft assembly from the ceramic housing end, no worries nothing will snag or get damaged. It will be in stages, just like the dimmer effect, the third pull will release the shaft.

10. Inspect the shaft assembly, I bet it is loose, sliding back and forth on the shaft. Maybe .5-1.0 mm. The shaft has a rubber washer, circlip, electrical contact assembly, angular contact, black angular spring, retaining pin, rubber washer (smaller ID).

11. Remove circlip, then slide forward to remove the retain pin. Assembly will now come apart. I used electrical cleaning spray and cleaned everything. Ceramic housing too.

12, Placed coat of Di-electric on all the parts & Re-assembled with a mod. Found a small SS washer the thickness of the slop and added it below the circlip. Tested that it rotated smoothly by using a pin too through the shaft side hole and held the electrical contacts and rotated for smooth movement. Done.

13. For extra measure, I pressed in the contacts of the ceramic housing to give a bit more tension after sliding the shaft assembly back in.

14. Locate the split contact prongs and slide the shaft in accordingly to the same paths left by years of use.

15. Test the assembly slides in and out with the proper stages as it would be mounted.

16. Use the screw/nut set to hold the assembly together. I used the dremel to cut the extra length off and placed some sealant at the cut ends.

17. Test to insure the rotary movement is still smooth yet snug (close to zero slop but not too tight), it should be smooth but better safe then sorry.

Mount:

18. I cleaned the terminals while I was there. Reconnected all the wires. In reveres order, I put the wired end in and up the dash then the shaft. Found the mounting hole and held it.

19. Replaced retaining nut by hand but not tight yet.

20. Replaced knob, do not over tighten it will just spin the housing in the back and may bind the wires.

21. Holding the housing from behind the dash, I positioned the knob to it's max dim up position and used the pin tool to tighten the retaining nut.

TEST:

22. Push in the knob to off position, connect battery, turn ignition to ACC position and pull the knob. It should be steady and slop gone = flicker gone. gauges should be brighter as well

Hope this helps someone.

My Humble Contribution,

Jim

[Boselly]

I have been having the same problem. I considered replacing it but not at $200 a switch. I'll give this a go soon and upload some pics.

[rusnak]

Haven't tried it, but it sounds like a very nice write-up. Great job!

[DRACO A5OG]

Originally Posted by Boselly

I have been having the same problem. I considered replacing it but not at $200 a switch. I'll give this a go soon and upload some pics.

Yeah unlike the Fog Light Switch, the Dimmer is more robust.

Your year is as stated in the Bentley, but I think only the Knob set up due to the "illumination". The main assembly should be the same.

I highly recommend the labels or something to to keep track of those wires that was the only thing that was scary, because some of those were piggy backed.

It took a little over an hour, like the hi-lo beam a very satisfying fix/mod.

----------

Hey Rusnak, thanks , Hell come by and I will help you fix it

[warner53]

I had my rheostat for the dimmer burn out. Is there a fix for that?

Warner

[DRACO A5OG]

Originally Posted by warner53

I had my rheostat for the dimmer burn out. Is there a fix for that?

Warner

Sorry I am not an EE do not know the terminology, as you can tell from my post

If you are talking about the internal coil (like a spring), that gives the lo-hi range output, that is what the middle rivet is holding in place.

I am sure it is a replaceable part at an electronic's specialty shop.

Have you taken yours apart to verify it is the rheostat thingy that is out?

J

[Wil Ferch]

Nice Work !!! .......

..... now finish the job by adding the dash lighting fuses to that headlight switch.... that Porsche "forgot"----->

Dash lighting fuse installation

[rusnak]

^ great idea!

[RSTarga]

rheostat in switch wears out

[schumicat]

good write up. the dimmer switch is kind of silly in this car, because its range is between "off" and "very dim."

[DRACO A5OG]

Thanks fellas!

Will upgrade to the fuse set of the blue/black wires which is the wiring for the gauges, but with the low voltage LED converter I think I will be OK, but better safe then sorry.

Agreed, it is a funny assembly, if you turn too much to the right, the housing nut will lose it's grip and spin causing the wiring behind to bind or too much to the left and the dang knob spins, very bad design, should have placed a locking mechanism. my 2 cents.

So far so good, nice a steady illumination of the gauges and knobs

[DRACO A5OG]

Originally Posted by Wil Ferch

..... now finish the job by adding the dash lighting fuses to that headlight switch.... that Porsche "forgot"----->

Dash lighting fuse installation

Thanks Doc Will,

Got er Dun!!! Easy as Pie, and took 5 amp mini fuse

Disconnect Battery, place fuse assembly before the Black with Blue wire connectors and heat shrink for safety, connect battery, SAFETY DEVICE ON

No dis-assembly required

[Wil Ferch]

DRACO:

If you got er done.... I have 2 questions....

1.) Notice in my original link I mention difficulty to gain access from below, because I had the trunk release "pull" welded metal triangle plate in the way....GeorgeK didn't. Did you therefore pull the switch from the front..as you originally did...to gain access?
2.) I would try 2A or 3A fuses...at least for stock dashlight wiring/ bulbs....

[DRACO A5OG]

Dr. Will,

1. No, I did not pull the Dimmer to gain access. But in retrospect, it would probably make it easier to see the wires and pull them off the terminals.

Indeed the plate was there, but if you push away carefully the surrounding wires you will see the wires as depicted in the pics of your link.

Apparently, when the Dimmer is positioned correctly, the wires should be in this order, first Red Hot Wire, then right behind it the Black/blue wire cluster as seen above ( it appears his assembly was twisted around ). I guess you could turn the dimmer assembly until the wires needed are easily viewed and accessible.

I used a needle nose to pull both connectors, attached the fuse assembly, the black/blue wire cluster and then the red wire.

2. Oh really, OK, back to the auto-parts store, I had my hands on the 3 amp fuse, thinking " I wonder???" You must have been transmitting your VooDoo

Jim