Temp/Fuel gauges read HIGH/LOW on my late mk2 Jetta..

[R.O.R-2.0]

so, the temp and fuel gauges on my car work, but not right..

the fuel gauge goes WAY above the full mark, and the temp gauge reads a hotter temp than the engine actually runs.

then, for some reason, both gauges will read correctly for a while, then read LOW. then go back to reading HIGH finally..

car runs out of fuel with 1/4 tank showing on the gauge..

also, my low coolant light OFTEN flashes, with the coolant tank full..

so, am i looking at bad grounds for the cluster? or am i looking at a bad cluster?

the temp gauge has NEVER worked right, as long as ive had the car. fuel gauge SEEMED to work ok tho.

im stumped guys. i just dont know where to begin..

[bbob203]

mine always read on the low side.

[cyrus #1]

I would start by checking your grounds, battery voltage, alternator, etc.  If those all check out I would move on to the instrument cluster.  There is a voltage regulator in the instrument cluster.  If it fails it could cause what you are describing.

[ORCoaster]

Voltage Regualtor on the gauge panel?  That little black box in the corner with the three prongs on it.  Sounds like it is not doing the job of keeping the voltage steady to the instrument panel.  

Do you have a spare?  I wonder if the cluster I just replaced on my MK1 would do the job.  The gauges always seemed pretty steady and on square.

[CRSMP5]

voltage stabilizer same on mk1-mk2.. so try it.. also that is 7v.. so a fyi on charging system and all.. when driving with bad alt.. when gauges stop working.. pull over.. car is abt to die...

[R.O.R-2.0]

NO, i dont have a spare to try. i only have one single CE2 cluster.. my Jetta is the only car i own that is that late of production.. all my other cars are mid-late 80s (CE1)

ive often wondered about it being grounds, or the voltage regulator..

at first, i thought it was JUST the fuel gauge. but then i noticed the TEMP gauge goes up and down with the fuel gauge. if one gauge reads high, then they both do.. ive never seen JUST ONE read high..

[ORCoaster]

It might actually be the ground on the voltage regualtor.  On the PC board itself.  A bugger to test in place and a bugger to test out of the dash too.  The solder that holds it in might just need to be refreshed and make a better connection.  That is where I would go as it is cheap, doable in short order and known to be a problem area.  I am not planning to be in Portland over the next weekend but that doesn't mean I can't put my old gauge someplace you can find it and you just pick it up if you are there.  I  know you want to drive the MOG. 

Let me know and I will throw it in the car so it is there while I am here. 

[billybobf]

I was gonna say, On my toyota I had a gauge that did not work right, it was a bad solder joint on the back of a gauge, heated it up, worked great now

[R.O.R-2.0]

its not just a SINGLE GAUGE tho. its all gauges that have a reading that is not speed or RPM.. my tach doesnt work right now, otherwise it would probably do the same. its a little harder to notice your tach reading high/low tho..

dale, i doubt you have any gauges that will even remotely work in my car. you have an EARLY rabbit dont you? i need a gauge cluster, or parts of one atleast, but they have GOT TO BE out of a 89-92 car (CE2 wiring)

[ORCoaster]

OK, I thought you might be able to salvage the voltage regulator off of it if that was your trouble

[R.O.R-2.0]

OK, I thought you might be able to salvage the voltage regulator off of it if that was your trouble

if the REG is the problem, i have an 84 rocco parts cluster and PC board with the reg still attached. also have the cluster out of my 81..

thanks tho.. i appreciate the offer.

[R.O.R-2.0]

well, the REG was the problem. it was LOOSE. not contacting the heat sink. i imagine it was getting HOT, and allowing too high of a voltage..

the low coolant light quit flashing, the temp gauge reads a little west of center (like it should with a 195* t-stat) and the fuel guage reads full, not above full, when the tank is actually full.

this fixed LOTS of issues that have been bugging me for quite some time..

[ORCoaster]

That's what makes this place such a useful site.  Those of us that know a little are dangerous, even unto ourselves but collectively we do great things.  Solved the problem and that was the mission.  Good that it was a simple fix as well. 

ya eh?

[R.O.R-2.0]

well, i was PREPARED to replace the regulator. even had a new one. but when i went to un-hook the old one, and it was loose, i disconnected it, cleaned everything, put it back together TIGHT like it should be, and now all is well..

looks like ive got a SPARE regulator now..

is it common for the regulator to have its own quick connector? i thought CRS said something about it being SOLDERED on?

[ORCoaster]

I thought they were soldered in as well.  Maybe on my 81 and then later on they went to the plug in style you have.  That is why I thought if you just touched it up with a soldering pencil it would cure itself of that haywire problem. Good to know some just plug and pray.  Might be a fix for a lot of those my gauges are wonky posts we see.