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HomeTech Articles > Solving Strange 944 Gauge Problems...

Pelican Guest Technical Article:

Solving Strange 944
Gauge Problems

Michael Van Bibber (AFJuvat)
Vanbibma@cfl.rr.com


Tech Tip: Strange Gauge Behavior in a Late (Series 2) 944.

I wrote this article after having some strange readings on my instrument cluster – to include: fuel gauge reading full when I just filled the tank, voltmeter constantly reading 12 volts.

My initial thought was a bad ground (especially for the voltmeter) and a bad fuel sending unit. However, after replacing some burnt out instrument lights, I found a fix that took care of them both – for no cost at all!!!

WARNING/DISCLAIMER: This procedure involves removing your instrument cluster and manipulating some of the electrical contacts on your gauges. If you don’t know what you are doing, or are unfamiliar with proper electronics safety (static charge etc..) DON’T DO THIS PROCEDURE! The instrument cluster is HIDEOUSLY expensive. Pelican Parts has replacement VDO Gauges, but the circuitry is a dealer only part – and they only sell it as a whole assembly – prepare to spend in the neighborhood of $1500 or more if you screw up. Of course, if you screw up, I am not responsible, you have been warned.

Tools:

24mm Socket (for steering wheel)
Phillips Screwdriver
Flathead Screwdriver
5, 6, &7 mm sockets
metal polish (Never dull works great)
alcohol wipes (or alcohol and q-tips)
Light bulbs (available from Pelican)
Personal grounding strap (Highly recommended)
Beer or other favorite tasty adult beverage


Procedure, Removal:

1.    Disconnect the negative battery cable

2.    Disconnect the fuse for the instrument panel (yes, I know, paranoid, but better safe than sorry)

3.    Remove the steering wheel

4.    Remove instrument panel trim piece

5.    Unscrew the instrument panel

6.    Carefully disconnect the three cables from the instrument panel.

7.    Remove the instrument panel from the car

8.    Take the panel and your tools to a clean, dust free area where you can sit and work.

Procedure, Instrument panel tune up:

1.    Place the panel face down on a padded surface (clean towel works well)

2.    Ground yourself using a ground strap.

3.    If you have them, now would be a good time to change out all of those instrument panel bulbs.

4.    Now, look at the back of the panel – on each side, where the combo gauges live, you see 2 black football (or rugby ball if you are in the UK) shaped objects with a brass nut in the center. Loosen these with the socket. After you have gotten the nut and washer off, lift the football shaped thing off of the circuit board. – these are the main electrical connects for the combo gauges.

5.    Clean the nut, washer, and the brass posts, as well as the threaded post sticking out of the circuit board with metal polish – then wipe down with alcohol to remove any residue.

6.    Reassemble, making sure the nut is SNUG (DO NOT OVER-TIGHTEN!!!!!)

7.    Repeat for the other footballs…..

8.    You will also see a few SILVER, FLATHEAD, screws – snug these up as well, once again, do not over-tighten.

9.    Clean the cable attachment points with alcohol

10.    In the Haynes style, installation is the reverse of removal.

Michael Van Bibber (AFJuvat)
Vanbibma@cfl.rr.com
Comments and Suggestions:
Matt Comments: I'll take all the help I can get. Is it safe to turn the key on with the gauge cluster out to check voltages at the three cluster ribbon cables?
August 29, 2014
SDisselhorst Comments: Which pin do I check? I have an Oscilloscope to see it, but don't know any of the pinouts. Is it a 12v pulsed signal to drive the speedo?
August 29, 2014
  Followup from the Pelican Staff: I don't have a wiring diagram for your vehicle, so I can't identify the pin. It will be a pulsed signal, anywhere from 5 to 12 volts. - Nick at Pelican Parts  
SDisselhorst Comments: On my 1986 944 5-Speed, the cruise works fine, but the speedo and odo do not work. I cleaned the connections, but no change. Do I have a bad speedometer? Could this be the broken gear? Could it be in the DME?
August 28, 2014
  Followup from the Pelican Staff: From your description I would assume the issue is in the cluster. I would check the signal from the DME to the cluster to confirm it is faulty. - Nick at Pelican Parts  
Matt Comments: Thanks for your reply, Nick. The lights that don't work are the fuel reserve, park brake, brake pad warning, brake fluid warning, and oil pressure warning. My parking lights, indicator and high beam bulbs do light up if they are in use. All three cluster connectors appear to be properly attached, so is there another connector further along the wiring that could be faulty?
August 28, 2014
  Followup from the Pelican Staff: The available wiring I have for your vehicle does not have instruments, my advice will have to be more generic.

I would check fuses and power feed to the instruments. There may e a faulty power or ground feed for the warning lights. - Nick at Pelican Parts
 
Matt Comments: I have a 1991 S2 which seems to run well, but has very few warning lights during the system check. Turning the ignition to on only brings up the big !, the seatbelt, ANTILOCK, and the battery voltage warning lights. All of these extinguish when the car is started.

I've taken the gauges out, all bulbs are fine and the circuit board and connectors all seem intact. Could these have been disabled elsewhere or is there likely to be something wrong with the cluster? Thanks, Matt
August 24, 2014
  Followup from the Pelican Staff: Could have been disconnected. What lights are missing? - Nick at Pelican Parts  
Mike Comments: Hi, I removed the cluster on my 1987 944 oval dash to replace the odometer drive gear. I've put it all back together, but have no power at all to any of the gauges and the indicators do not work. I have checked fuse 18 and this is good - any suggestions?
July 24, 2014
  Followup from the Pelican Staff: Do you have power at the cluster connector? While checking, check for ground as well. - Nick at Pelican Parts  
Comet Comments: I have a 1984 944. The low fuel light is always on. The tank unit has been replaced so I believe that is ok. Any ideas or suggestions?
June 2, 2014
  Followup from the Pelican Staff: If the fuel gauge operating properly? If so, the low fuel light is fed a signal through the fuel gauge. The problem may be in the cluster printed circuit or the gauge. The fuel gauge signal to the cluster is on Pins 8 & 9.- Nick at Pelican Parts  
misterc01 Comments: Making progress - disconnected the negative battery cable to clean terminals and discovered the PO had wired in an extension so he could use a wing nut connection to easily disconnect the battery due e to a suspected drain on battery. Removed it, cleaned both terminals and a whole bunch of stuff seems to be working better. Due to the extreme weather, have not been able to go further yet. Thx for info. BTW - he has also connected a cable to manually move the temperature control for heating and cooling bypassed any sort of HVAC valving and need to know where there are some good pix to try and return the car to normal - or normal for a Porsche I guess:- Thx
March 28, 2014
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
Misterc01 Comments: Okay - here goes: Start car, gauges work fine. Turn on headlights, all gauges shut down. Turn off headlights. They proceed to go up and down. Shut the car down, headlights finally settle in for the night. Restart, have gauges. So far: pulled relays and they test good as far as solenoid working clicks. Pulled, checked and cleaned all fuses. hat did fix the door buzzer. Now brake also don't work. Hatch does not work. Oh yeah - I have had the car for about 53 hours and other than those little issues it drives really nicely. ...............
March 22, 2014
  Followup from the Pelican Staff: Sounds like a faulty alternator. I would perform a charging system test. - Nick at Pelican Parts  
jc Comments: Checked fuses, all good. Pull the cluster I assume?
March 16, 2014
  Followup from the Pelican Staff: Yes, you will need to confirm the cluster is getting sufficient power and ground. - Nick at Pelican Parts  
JC Comments: My whole intrument cluster works great; except for the speedometer and the tachometer. What should I do, check, etc to fix. I bought the car and it did not work.
March 6, 2014
  Followup from the Pelican Staff: You can start by checking the fuses, powers and grounds to the cluster. - Nick at Pelican Parts  
Judgecanaan Comments: Hello, 88 944 here. My instrument panel has stopped working for the most part. The blinker indicator still works though. Everything else = nothing speedo, tach, odometer, gas gauge, oil, etc.. Except on the rare occasion I drive the car to any extent and hit a bump, boom. The car will ding like I just started it and everything works again. Guessing a bad ground somewhere, what should I look at specifically?
February 8, 2014
  Followup from the Pelican Staff: I would remove the cluster and test the ground. If it is faulty at the connector, just a run a new wire to chassis ground. This is the quickest way to deal with it. - Nick at Pelican Parts  
tweeti Comments: Hi i have a 1987 944 turbo the Tachometer has just stopped working is it the gauge or something else don,t know were to look help
December 14, 2013
  Followup from the Pelican Staff: You can check the tach signal to the gauge, if it is present, the gauge is faulty. - Nick at Pelican Parts  
John_AZ Comments: Member Gawernater has put detailed DIY pictures on the forum and explained his method and preservation of ground cleaning.

http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/730190-my-first-electrical-project.html#post7224814
J_AZ
January 23, 2013
  Followup from the Pelican Staff: Thanks for the Info. We appreciate it.
- Nick at Pelican Parts
 
My Porch Comments: Thanks Pelican ! My 88 Turbo S has always had the fuel gauge read 3/4 full when it was just filled, and the voltmeter read 12 volts when it really was 14 volts. After removing the cluster and following the cleaning procedure for the connectors and putting it back together the gauges now read correctly. BTW, I was able to "wiggle" the cluster out of the dash without removing the steering wheel & airbag.
November 13, 2012
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
errol Comments: my 944 1987 porsche wont start I have checked & all spark is ok for example spark ok on plugs, i have made sure i have fuel yey when you disconnect fuel line & turn engine by ignition key fuel does not come out of line
October 23, 2012
  Followup from the Pelican Staff: I would perform a fuel delivery system test. Check fuel pressure, volume and quality.
Then check power to the fuel pump. - Nick at Pelican Parts
 
frankle951 Comments: Hi, I have 1991 944S2 cab, the fuel gauge stop working after I put gas in the car, the low fuel light stay on, the rest of my dash gauge work fine, no issue, so do I still pull my gauge out to check it or do I drop the tank ??????
September 11, 2012
  Followup from the Pelican Staff: I would gain access to the fuel level sender wires and test them. This would be easiest. Ground the wire, the gauge should read full. - Nick at Pelican Parts  
gtrope Comments: Hello Wayne, I've got a 944 Turbo Cup from 1987. The instrument panels and gauges are the ones of the 250 CV. After warmin the car without driving, my temperature gauge reflects a temperature between 90C and 100C 2nd bar. My Voltmeter reflects 12.5V, while measured at the battery, I read 13.20V. When running, even after a 100 meters, the temperature flights to the red, Voltmeter goes down arround 12V-, and I now frequently have an alert for low oil level... All very frighting!
I therefore spent 2 days cleaning all grounds, connectors, and sprayed some dry electronic bomb on the printed electronic board, as well as double checking the temperatures, fuses, relays, measuring all loss of Volts everywhere... But still no progress, appart from the fact that I'm not scared for more vital issues! What do you recon? Any idea?
August 12, 2012
  Followup from the Pelican Staff: I would check the volt meter is getting the correct voltage. if it is, yet the gauge reads low, you have a bad ground or a bad gauge. Try adding a ground directly to the battery and see if it helps. - Nick at Pelican Parts  
944S2 Comments: Hi I just bought 1990 944S2. I put some gas because it shows low. the gauge went up full but never came down after I drove 200miles. What should be the problems?
August 5, 2012
  Followup from the Pelican Staff: This could be a bad fuel level sender or gauge. Try unplugging the fuel level sender. If it reads empty, the sender is faulty. - Nick at Pelican Parts  
944 N more Comments: I have a '84 ,944 the alternator light came on.. I replaced the alternator and yet the light comes on.. what else can I look at ?? battery is only 8 months old only 2 wires to the alternator..
July 1, 2012
  Followup from the Pelican Staff: Do you have power at both wires at the back of the alternator? If so, check that the small wire is not open or shorted leading to the alternator light. You might have a defective alternator.- Nick at Pelican Parts  
BUDD Comments: 1983 Porsche 944...storage for 18 years, 49K miles.
Everything works except gas gauge and low fuel lamp indicator. Drained tank, new pump, new filter. Checked fuses, still nothing...the gauge is extreme left buried empty.. I hope I don't have to remove tank. 7-8 hours.
Please....anyone...HELP HELP HELP HELP ty.
March 2, 2012
  Followup from the Pelican Staff: Gain access to the wires and test the circuit. When disconnected tank should read empty, them ground wire, should read full. This will help you rule out or condemn the sender. - Nick at Pelican Parts  
Leonel Comments: Can't figure out how to take the Ignition switch off on a late model 944, all the inline instructions are for the te 85.5 and earlier model. Any tips?
February 25, 2012
  Followup from the Pelican Staff: Here is some info from our forums:
Hello, In order to remove the Ignition Key Lock cylinder you have to drill a 1/8" hole in the right location to release the spring. If you can all ready see the broke off torque bolts you must have the gage cluster out. The easiest way to remove the bolts is to use a Dremel Tool with a cut off wheel. Grind a slot across the end of the bolt (on top) so you can use a common screwdriver to turn the bolts back out. You can use common cad plate bolts and lock nuts when you re-install. Below is where you drill the hole. Put a small screw back in the hole.





http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/548390-how-do-you-remove-ignition-switch.html - Nick at Pelican Parts
 
Rufus Comments: I have a 1983 944, my fuel guage and speedometer does not work. My fuel light doesnt even come on. The fuel guege needle pegs out past full and never moves until the car is turned off. Any help with this? The speedometwer doesnt work at all. You can here a clicking sound in teh dash while you are driving. All of the dash lights work fine.Can anyone help with this? Thanks
February 22, 2012
  Followup from the Pelican Staff: I would check the fuses and grounds to the cluster. If they are all malfunctioning, the fault is shared and shouldn't be too hard to find. - Nick at Pelican Parts  
porsche man944s2 Comments: hi ive a 1987 porsche 944 s2 its was running fine and battery run flat over 2 weeks replaced battery with a new 1 and none of the gauges on the dash are working do you have any ideas i have checked fuses but all seem ok is there a relay for them any where your help is appreciated
December 10, 2011
  Followup from the Pelican Staff: Did you have to jump start the car? is it possible that the cables were crossed? Electrical circuits can be damaged if this is done. - Nick at Pelican Parts  
Steve Comments: I have a 1986 951. The tachometer and turbo boost do not function, but almost everything else does. Everything seems to be plugged in where its supposed to be. You said you do repairs, but I'd have to send you the entire cluster, correct? Also, my odometer does not work. Understand this is a common problem. Can this be repaired?
July 12, 2011
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you figure out what repair options there are. - Nick at Pelican Parts  
jhl Comments: The tachometer in my 1986 944 Turbo now pegs out past the red line when started. All of the other gauges appear to work correctly. Any suggestions to this symptoms are greatly appreciated.
June 20, 2011
  Followup from the Pelican Staff: Check the ground to the tach and the signal in using a scope. If they are good, the tach is faulty. - Nick at Pelican Parts  
BURT Comments: I HAVE A 1990 944S2 THE ODOMETER STOPPED WORKING, IS THAT A BIG JOB ,THAT'S THE ONLY THAT DON'T WORK
April 22, 2011
  Followup from the Pelican Staff: There could be a faulty odometer gear. You may be able to repair that or replace the speedo. Give our parts specialists a call at 1-888-280-7799. They can help you - Nick at Pelican Parts  
Brian Comments: I have an issue where I have a 7.5 amp fuse in the circuit for the passenger headlight/fog light. I replace the fuse and turn the light on and it works. When I turn the lights off and later turn it on again, the fuse blows. I have replaced several with higher amp fuses just to guess how much current I am actually drawing. So far, I have blown fuses up to 25 amps. Any suggestions orhter than a complete rewire from the fuse panel to the light?
March 23, 2011
  Followup from the Pelican Staff: I'm guessing that you have some type of short in your headlamp switch. I have seen this many times before on other cars I have owned, although not exactly in this pattern. I would replace the switch and see if the problem disappears. - Wayne at Pelican Parts  
scooter471 Comments: 1988 944 s. Odometer and tripmeter not moving. The rest of the dash seems fine. Speedometer, fuel gauge, tach, oil, voltmeter all fine. ?? get it rebuilt??
October 17, 2010
  Followup from the Pelican Staff: There could be a faulty odometer gear. You may be able to repair that or replace the speedo. Give our parts specialists a call at 1-888-280-7799. They can help you - Nick at Pelican Parts  
Craig Comments: I own a 1991 944 S2 Cab. The fuel gauge is not working it is all the way down. My mechanic changed a A/C relay and it seemed to quit working maybe a coinsidence however it is not working now. The yeloow reserve light comes on that is the only way I know to fill up Can you help? Craig
October 14, 2010
  Followup from the Pelican Staff: He probably bumped the connection to the gas tank level sensor. I would check the top of the tank and look at the sensor and/or simply take it back to him and ask him to replug it in. - Wayne at Pelican Parts  
Porsche Loyalist Comments: Ok thanks, where exactly are those connections I should be checking, are they directly behind the dash itself or under the hood as well?
August 22, 2010
  Followup from the Pelican Staff: Should be right behind the dash, but the problem is most likely with the gauge itself... - Wayne at Pelican Parts  
Porsche Loyalist Comments: I own a 1986 944 and my tachometer no longer works, whats the problem?
August 22, 2010
  Followup from the Pelican Staff: I would check the connections to the gauge, and/or the gauge itself. If you can find a replacement unit to plug in to test, that would be ideal. It's most likely the gauge itself. In some cases, these can be rebuild (we do this too), for about $150-$200. - Wayne at Pelican Parts  
jzrasmusson Comments: I have a 1987 944, the shift light and the MPG gauge seem to only work when the car is cold early morning. If you drive it long enough or turn off the engine after it's been a few minutes the shift light and the MPG gauge stop working again. I know these gauges are pretty much useless in general but it drives me nuts that I can figure out why they only work on really cold mornings. Any suggestions? Thanks!!
August 9, 2010
  Followup from the Pelican Staff: Hmm, the only thing I can think of is that there's a wiring connection that is becoming loosened when the car heats up. I've seen this sometimes on older cars. - Wayne at Pelican Parts  
Surfman1124 Comments: Got a 1985.5 Late NA Porsche 944. The Tach will run fine some times, but it will go up about 2,000 RPM over what I am running. If the car is running about 3,000 RPM, it reads 5,000 RPM. The car runs great, but it is kinda annoying. Any ideas?
May 28, 2010
  Followup from the Pelican Staff: The only suggestion I have is to have the tach removed and tested to see if it's broken or not. Or buy a used one on eBay for $10 or so, and see if it works more reliably? It sounds like an issue with the tach itself. - Wayne at Pelican Parts  
Tom Comments: Have a 85 1/2 944. Speedometer and odometer don't move. Just replaced the whole instrument cluster and still no fix. Any suggestions?
April 19, 2010
  Followup from the Pelican Staff: There could be a faulty odometer gear. You may be able to repair that or replace the speedo. Give our parts specialists a call at 1-888-280-7799. They can help you - Nick at Pelican Parts  
porsche4life Comments: http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/513424-dismantling-gauge-cluster.html
I took a cluster apart and posted in the forums... Go check it out....
November 28, 2009
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
jj Comments: I try to restart my 1986 944 none turbo had been park in my garage for 6 months but, it does not cranking up at all. Can any body help for any possibility problems to fix it. Thank you so much
November 10, 2009
  Followup from the Pelican Staff: Sounds like a dead battery, I would try putting a battery charger on it and seeing if that helps? - Wayne at Pelican Parts  
paul Comments: i have a 1986 944 porsche. the speedometer needle goes up to about 20mph then stops regestering. can you give me any hints? thanks paul
November 10, 2009
  Followup from the Pelican Staff: Not off the top of my head. My only real recommendation is to pull it and have it rebuilt. Or find a good used one on eBay? - Wayne at Pelican Parts  
matt Comments: My needle doesn't move either. I let the gas pump automatically and ended up overflowing the tank. Is it the same problem?
October 7, 2009
  Followup from the Pelican Staff: There are multiple problems if the tank is overflowing. If your needle is not working then you probably have a defective gauge sender. - Wayne at Pelican Parts  
Bruce Comments: Thanks so much for the info on the S2 with the airbag.
October 3, 2009
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Bruce Comments: I have a 1990 944S2 and the speed gauge connection seems to be loose as it shows the speed but then suddenly can drop to zero.There is an airbag on the car.How to remove the steering wheel when there is an airbag?
Thanks for the info that you have provided,and for taking the time to type and post it!
October 1, 2009
  Followup from the Pelican Staff: The airbag is attached with two bolts from the rear of the steering wheel. I believe it's similar to the Boxster and BMW 3-Series - check those articles for more detail. The speed sensor is located on the transmission I believe on the S2 - check the connection, and/or replace the sensor. - Wayne at Pelican Parts  
DRAWLI Comments: THANK YOU FOR THE INFO
August 2, 2009
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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