[Velocity]

Several months ago, I noticed my speedometer occasionally dropping to zero while driving - it would start working again shortly, then fail again.   I cleaned the speed sensor in front wheel and it hasn't happened since, so possibly unrelated to my current issue.

 

Recently (as in a week or two), I noticed ALL my dash gauges would stop working, but when then start working again for a bit, only to stop again.   During these "dead dash" incidents, the speedometer would partially work (ie, might register 15-20mph if I was going 45).   Also, oddly, the AC compressor would not run when dash was dead.   IF dash came back, compressor would start up again and I'd get cold AC.

 

Given I've seen/heard of bad grounds causing odd error such as this, I spent some of last weekend cleaning off at least two (maybe three?) grounding points I could find in the engine bay as well as the two under the dash/above the clutch inside the car.   They appeared fine, but went ahead and lightly sandpapered each ground contact and sprayed DeoxIT (https://www.amazon.com/DeoxIT-D5S-6-Cont...B0002BBV4G) on each of them prior to reconnection    Didn't get a chance to drive it last weekend, but started it up yesterday and all dash gauges were dead.     Exterior lights work fine, however if I put on hazard lights, several attempts resulted in hazards blinking ONCE then stopping.  A couple of times they continued to blink in a normal pattern.   Very odd....   Master warning light (red triangle indicator) does NOT come on when dash is dead, even with parking brake applied (which it normally does).   However, the low fuel light (red area in bottom part of fuel gauge) does come on with power to car (key on) and ignition off.

 

I checked fuses for dash and a couple of others, and fuses themselves appeared fine, but I did notice what looked like some corrosion in the fuse socket itself.   Does anyone know if it'd be safe to spray a bit of the contact cleaner/DeoxIT into the fuse socket itself?   Any other way to "clean" the fuse socket?    Edit - I later realized that that same fuse (#38) that covers the "instrument cluster poti" also has the license plate light...which IS working correctly, and 18, which covers "instrument cluster" also covers the "gong relay" and the gong works as well -- so I do NOT think it's fuse related, at least not those.

 

   

 

Any other thoughts of possible root causes for these wacky symptoms?

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[Velocity]

The plot thickens - I took the 968 on a 15 minute drive thru my neighborhood tonight.   For the first 5 minutes, the entire dash was dead - with exception of indicator on bottom of fuel gauge as I started it and turn signal indicator when it was used.   The AC compressor was also not working, but fans ran across all settings.

 

About 5 minutes into the drive, I made a right hand turn, signaling as I did so, and the dash came back to life.   AC compressor kicked in a few seconds later.  Nice cold air, and all gauges worked normally.    Engine oil warning light was on, as well as airbag light and master caution.   Oil pressure (both stock and aftermarket gauges) and level (checked it right before I went for the drive) was fine.

 

Completed the rest of the drive - going over speed bumps, several turns, a couple of acceleration runs, etc - trying to jostle the dash around to see if I could get the dash to shut down again, but had no problems.   Once I made it back home, I turned car off (with dash still acting normally), went inside to get laptop to use durametric to check errors, and as soon as I turned car back to ignition on/engine off, the dash was dead again.  grr....

 

Durametric showed NO errors for engine computer, and the following errors for airbag :

 

   

 

I think these errors are an indicator of some type of disconnect/reset or similar and not actual airbag problems.  I've seen them before when battery was disconnected, and once cleared, they stayed gone until a similar battery reset occurred.    Oddly, this time, I could reset them, see they were cleared :

 

   

 

...yet as soon as I'd scan for codes again, the same ones would show up.

 

So - any guesses on further troubleshooting steps given all my wacky symptoms?   

 

Unless anyone has a better idea, I think I'll pull the instrument cluster and clean any connectors/grounds I could find. 

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[oppositelock]

No help other than to say you're probably on the right track. I've attached two sheets for the ground point diagram so you can double check you've cleaned them all.

 

Ground Map.pdf Size: 248.79 KB  Downloads: 29

Ground Points.pdf Size: 316.74 KB  Downloads: 27

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[lbpesq]

Was your car previously owned by Linda Blair?

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[Velocity]

Was your car previously owned by Linda Blair?

 

Hah, hadn't seen her name on previous owners list, but it's certainly possible!   Even more likely, I suspect one of her relatives worked for Porsche ion the electrical system design group.  :-)

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[Velocity]

I spent several hours working on the car again today trying to fix this "intermittent gauge cluster dead" issue.   

 

Started off by pulling the battery out of the car.   Immediately found another ground point in battery bay, and this one had significant corrosion/crud on it:

 

   

 

Got it cleaned up and reconnected and thought "could it possiblly have been that easy"?    Went ahead and reconnected battery and started car.   Nope - gauge cluster still dead.

 

Pulled battery again and started removal of instrument cluster.   Once removed, I used a pencil eraser to clean the connections for the 3 ribbon cables (which looked fairly clean) on the cluster pod.   

 

Also removed 3 of the 4 "football connectors" and cleaned those, the posts they attached to, the washer and the brass nut for each of them.   Rinsed each with De-oxIT and reassembled.  Each of these had very minor discoloration, but were relatively clean.

 

   

 

I could not get the 4th "football" connector off because it was covered by some type of electrical component (capacitor?) and I didn't want to break that.  In fact, as I touched that component covering the "football connector" on the right side of the below picture, it felt somewhat "loose" to me -- would rock back and forth a bit.  not totally disconnected that I could tell, but just didn't feel "solid".   

 

   

 

The only item I found that seemed odd on the whole cluster was a bit of yellowish powder/stuff on one area of the circuit ribbon - can be seen in following picture:

 

   

 

Almost looked like there was some sticker or something on there at some point, it had fallen off, and this was leftover residue from the adhesive.  I scraped away a bit lightly with a plastic tool but didn't want to mess with it too much for fear of damaging the ribbon circuits themselves.

 

I'm hoping that's all there is from an "electrical connections or grounds" perspective in the cluster?  That's all I could find from some research here and on RL.    

 

After completing the cleaning of all the above connectors, I reinstalled the cluster (losing the bottom left of the 4 screws that attach the cluster itself down into the lower left dash - dammit). 

 

Reinstalled/reconnected battery and restarted car.    Dash was still dead.     Sigh.   

 

Also did the following additional work "just to see if it'd help" :

• replaced a handful of fuses (including both of the ones that are labeled anything to do with the instrument cluster and airbags) with brand new ones.  Older fuses had darkening at connectors, but were not blown.   
  
• Cleaned additional ground point in passenger floorwell (near airbag control unit).   It looked pretty pristine, but cleaned it anyhow.
  
• Replaced my "window regulator" relay with a spare I had.   I'd noticed while doing some earlier troubleshooting (in the fusebox) that this relay seemed to run excessively hot with the car on - as in upwards of 120F - painful to touch.   Windows had been working fine, so was only chance I noticed it.  So far, the replacement one does NOT seem to run hot, so guessing my original relay was going bad.    Don't think that'd be related to my primary issue, but replaced it anyhow.
  

Tried one last time with starting car.     Gauge cluster still dead.   As mentioned before, I DO get the "low fuel light" at bottom of range of fuel gauge lighting up, and if I turn on parking lights, the parking light indicator comes on, so the cluster DOES have some power, just appears to be getting NOTHING from DME/computer/main harness. 

 

I'm officially stumped.   At this point I suppose I'll try and watch it to see if I can discern any pattern as to when it DOES intermittently work (like it did on my test drive yesterday).   Honestly, I miss having the AC compressor working when it's in this failure state more than I do the gauges themselves.  ;-)   

 

This is going to be a problem when my yearly vehicle safety inspection comes around - suspect it won't pass in this state.   If it doesn't clear itself up or I can't figure it out, I suppose I'll have to see if a shop can trace it down. 

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[Velocity]

No help other than to say you're probably on the right track. I've attached two sheets for the ground point diagram so you can double check you've cleaned them all.

 

Ground Map.pdf

Ground Points.pdf

 

Thanks for these!   

 

I already had like 4-5 different charts of grounding points (I think some from 944 instead of 968), but oddly NOT this one.   I actually like the "battleship coordinates" version of "find the GP" that's available with this one - printed out both pages to keep in my shop and will try to track down the few I haven't got to yet.

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[MCL968]

I have said this before, but it seems oddly appropriate given these symptoms. Our ignition switches are getting old and they are failing in some curious and unpredictable ways. My heater would go on and off at random times, and there were a few other strange things that also disappeared with the new switch. If you already have the dash out, you have nothing to lose. It's not a terribly difficult job, but I suggest replacing the long slotted screws that hold it to the lock cylinder with allen head ones to make installation easier. And get the proper switch, the dealer tried to sell me one that needed to have the wires swapped and soldered. Not happening, the right one is out there, get it and be done with it for another 30 years.

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[Waylander]

Absolutely what Matt says, the ignition switch block on the rear of the lock

You can experiment by starting the car then when the key is in the run position, just gently try turning it back towards position 1



These cars do all sorts of crazy things with a worn switch

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[Velocity]

I have said this before, but it seems oddly appropriate given these symptoms. Our ignition switches are getting old and they are failing in some curious and unpredictable ways. My heater would go on and off at random times, and there were a few other strange things that also disappeared with the new switch. If you already have the dash out, you have nothing to lose. It's not a terribly difficult job, but I suggest replacing the long slotted screws that hold it to the lock cylinder with allen head ones to make installation easier. And get the proper switch, the dealer tried to sell me one that needed to have the wires swapped and soldered. Not happening, the right one is out there, get it and be done with it for another 30 years.

 

Interesting... I'll try and test this tonight (using the method waylander mentioned).     

 

A couple of quick questions:

• Do you have to remove full dash to get to the ignition switch?  To pull the cluster I just took the cluster bezel/surround out and removed the cluster thru the dash - didn't remove the dash at all.
  
• Is this the part you're talking about?   1992-1995 Porsche 968 Ignition Switch 944-613-024-01 | Sunset Porsche Parts
  

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[MCL968]

 

 

Interesting... I'll try and test this tonight (using the method waylander mentioned).     

 

A couple of quick questions:

• Do you have to remove full dash to get to the ignition switch?  To pull the cluster I just took the cluster bezel/surround out and removed the cluster thru the dash - didn't remove the dash at all.
  
• Is this the part you're talking about?   1992-1995 Porsche 968 Ignition Switch 944-613-024-01 | Sunset Porsche Parts
  

 

Yes, the part numbered 10 is the switch.

 

Just remove the cluster and the lower covers. The screws are small slotted ones that are long so they can pull the switch into the key mechanism. The connector is a bit of a challenge, but no more than on other cars. All in all a couple of hours at most.

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[Velocity]

Yes, the part numbered 10 is the switch.

 

Just remove the cluster and the lower covers. The screws are small slotted ones that are long so they can pull the switch into the key mechanism. The connector is a bit of a challenge, but no more than on other cars. All in all a couple of hours at most.

 

Thanks.   

 

I did go on another 10-minute drive tonight.   Jiggled the key while driving, tried switching back to position 1, even tried "percussive maintenance" (smacking the lower dash near the ignition) and never got the dash back.   

 

Waylander - by "You can experiment by starting the car then when the key is in the run position, just gently try turning it back towards position 1" - did you mean similar test to what I did above, or something else?

 

The dash definitely still has power (after my "recondition attempt" over the weekend) - the turn signal light works, low fuel light works before start, and if parking or headlights are on, dash background lights come on, but gauges still show nothing.    Actually, once change since the cluster work I did over the weekend - this time around the fuel gauge did move between 1/4 and the bottom of gauge a few times - not "ranging" across that area, it was either dead on bottom of gauge or right at 1/4.    Guess at times it was getting partial signal.

 

Anyhow - the ignition switch theory does make some sense as the gauges in the cluster (and the AC compressor) appear to think the car is totally off when it's actually running.  Guess I'll order one and give it a shot given it's a (relatively) cheap part.

 

I greatly appreciate everyone's help!

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[Velocity]

 

[...]

The dash definitely still has power (after my "recondition attempt" over the weekend) - the turn signal light works, low fuel light works before start, and if parking or headlights are on, dash background lights come on, but gauges still show nothing.    Actually, once change since the cluster work I did over the weekend - this time around the fuel gauge did move between 1/4 and the bottom of gauge a few times - not "ranging" across that area, it was either dead on bottom of gauge or right at 1/4.    Guess at times it was getting partial signal.

 

Anyhow - the ignition switch theory does make some sense as the gauges in the cluster (and the AC compressor) appear to think the car is totally off when it's actually running.  Guess I'll order one and give it a shot given it's a (relatively) cheap part.

 

I greatly appreciate everyone's help!

 

Well, I had the ignition switch replaced (by a shop) with a new part this morning, and.......nothing.   Symptoms are still exactly the same.   

 

Shop wants up to 5 hours to diagnose, potentially pulling dash and checking electrical connections thru the firewall.   Before I commit to that, I want to exhaust my "at the home shop" options (ie, stuff I can do myself).

 

Two questions:

 

1. How difficult is it to remove the underhood fuse/relay box, at least enough to remove main wiring connection, clean, and reconnect?   That's the only other "common point" I can think of for both the AC compressor and signal to the dash gauges.

 

2. If it was JUST the gauges acting up, I'd suspect an issue with the gauge cluster connectors/wiring, or maybe even the printed circuit board, but the fact the AC compressor is off when dash is dead but works fine when I get dash back (a pattern that has repeated twice) makes me think it HAS to be something outside the cluster itself.     Can anyone come up with a reason the AC compressor would not work IF it was an issue with the gauge cluster/circuit board?    I'm trying to determine if there is still a chance it's something in the cluster itself, or NOT.

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[Waylander]

I would take a guess that you would need to follow the power and grounds for both to see if they come from the same source



The wiring diagrams are available at www.pdlibrary.co.uk

There is also a guide on how to read them,



The main fuse box has two plastic screws from inside going down, you can undo these and lift the whole base of the fuse box up a good few inches

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[unknown4u]

In answer to question 1. Not difficult to do.



Perhaps you can check first with the ignition on to push at the underside against the connectors. The connectors are secured with a main clip. If one is not secured you will easy find it. Because you can pull it off. Others not.
If there is a connection failure you will notice it very quickly.

I had it in the past when i bought the car.
Car stopped because the petrolpump didn't run anymore. The cause was a wrong mounting of the external alarm.

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[Velocity]

Well, for anyone still following along (and for future people coming across this with similar symptoms) the issue has been tracked down to.......the underhood fuse box.     

 

The shop I use found that fuses 18 (which is one of the fuses for the instrument cluster) and fuse 19 (which covers brake lights) were only putting out between 3v-8v power.   Did I mention that I also noticed brake lights weren't working either (final straw that made me take it into the shop).

 

Removing and disassembling the fuse box revealed this :

 

   

 

   

 

   

 

   

 

   

 

   

 

   

 

I haven't seen the fusebox yet to determine exactly where it's scorched, but I have to imagine it's it in the path to the two fuses (18 and 19) that had low voltage, and likely EITHER the G19 relay or fuse 29 (both of which involve the AC compressor).     That would explain all of my symptoms.

 

I had them swap the entire fusebox (part 944.610.110.00) with a used one I sourced off ebay, and everything (except for my stock oil pressure gauge) is working again.    

 

My only thought to root cause is that it may have something to do with the "hot G7 relay" issue I noted earlier in the thread - either the relay was dying and took part of the fusebox conductors with it, OR the issue with the fusebox conductors caused the hot G7 relay (but if so, seems odd that the replacement relay I swapped it out with seemed to be stable from a temp perspective).

 

In any case, hope that particular poltergeist has been exorcised from my cars electrical system for good.  ;-)    I'll pick the car up in a couple of days and we'll see!

 

 

 

 

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[tejon007]

Congratulations on figuring out the problem! And thank you so much for documenting it.



Personally, I hate electrical problems , especially when it comes to cars like the 968 that have fewer and fewer spare parts available...I worry that someday something will break that is either unavailable or unfixable.

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[unknown4u]

Everything is fixable, only have patience. ?

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[Velocity]

Congratulations on figuring out the problem! And thank you so much for documenting it.



Personally, I hate electrical problems , especially when it comes to cars like the 968 that have fewer and fewer spare parts available...I worry that someday something will break that is either unavailable or unfixable.

 

Yes, the parts issue worries me too.    From a "new" perspective, the fusebox is either NLA, or approx $1400 USD depending on where you look.

 

Luckily, since it's shared with the 944, there seems to be a fairly plentiful supply on ebay for $60-70.  ;-)

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