WHAT have i done to my poor car!?!? - PeachParts Mercedes-Benz Forum

Peyton300TD · #1 04-13-2003, 06:46 PM

what have i done to my poor car!?!?

i took out the instrument cluster today to work on putting chrome rings around the circles. first of all, i couldn't get the oil pressure thing off using an adjustable wrench. it began to strip so i quit trying.

the important problem is, however, that when i put it all back together and drove off, my temperature guage and fuel guage bounce like crazy. the thing is, this only happens when the wheels are rolling. when i come to a stop it doesn't happen.

i think i fried something on my circuit board because i touched metal to a connecter by accident and i saw a wee bit of smoke.

then when i try to turn the car off, the engine stays on, but the rpm tach turns off. vacuum disconnection i assume

HELP PLEASE!!! have i done something horribley wrong to the electrical system? or did i just plug something back in the wrong place!?!

psfred · #2 04-13-2003, 06:55 PM

Sounds like the electrical connection for the temp gauge is loose and that you managed to catch the vac line to the shutoff switch and pull it loose.

Pull the cluster again and make sure the electical plug is installed completely, and take a look at the key switch. Dollar to a donut you snagged one of the vac lines while unscrewing the speedo cable, and the fix will be just plugging it back in or splicing it with some vac line if it broke.

If you actually removed the temp gauge, check that the screws are completely tight. Best to turn them backwards till you feel the thread drop into the old groove in the hole, they turn in easier that way.

Peter

Peyton300TD · #3 04-13-2003, 07:46 PM

you're right about the vacuum.

in regards to the bouncing of the other guages, could it have something to do with the rolling of the wheels.... or the speedometer?

one other thing that happened was i accidentally touched a peice of metal to the back of the cluster and saw a bit of smoke rise up from a different area. could i have fried the circuit board?

eric

edge · #4 04-13-2003, 08:02 PM

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Is the the vac line to the shutoff switch behind the instrument cluster? I have a shut off problem and I could not find a loose vacuum line in the engine compartment or underneath the driver's kick panel. Thanks.

psfred · #5 04-13-2003, 11:13 PM

Eric:

Yes, you could have toasted the traces so that you only have a connection through something else rather than directly to ground (this is called backfeed). Always take the negative battery cable loose when doing the instrument cluster so you don't short anything.

The only way to check is to remove it, so you are back to the oil line. You need a line wrench to get that fitting off, or at least a proper size metric -- adjustables will always round such fittings off.

Edge:

There is a vacuum switch on the back of the key switch for the shutoff, and yes, it can leak, either the switch or the rubber connectors or plastic lines. Test with a vac pump -- the line to the switch must hold vac in either key position, on or off.

The supply to the switch is brown, the line to the shutoff solenoid is brown with a blue stripe.

Peter

Capt Kirk · #6 04-14-2003, 12:29 AM

it's either a 8 mm or a 10mm (I forget because last time I was in there I had both in my hands, just forget the one I used)

Also, that smoke is what we like to refer to as magic smoke that makes stuff work. You let it out, now it doesn't work.

Dunno if they sell it in bulk or not.

Peyton300TD · #7 04-14-2003, 09:48 AM

thanks for your advice! so in order to fix this supposed 'short' what do i need to do?

would it involve some soldering? or replacement (ugh)

eric

Capt Kirk · #8 04-14-2003, 02:47 PM

well you need to find where the short was.

depending on what was fryed it could be simple or difficult to fix.

get a Volt/Ohm meter and test in the area that you shorted out the circuit board

#9 04-14-2003, 03:19 PM

Do yourself a favor and throw away that adjustable wrench and buy yourself a set of tubing wrenches. Don't get near a brass fitting with anything except a tubing wrench ever again.

Good luck,

Peyton300TD · #10 04-14-2003, 07:42 PM

FINALLY i removed the cluster sucessfully and i fixed the vacuum! coincidentally, the vacuum was disconnected from inside the engine compartment, unrelated i guess.

anyways, to look for the short on the circuit board, i imagine i have to remove the panel on the right? but i hear that removing the speedometer panel is a PAIN in the rear to put back together?

any ideas?

Peyton300TD · #11 04-14-2003, 09:38 PM

hey i updated the mystery with a new thread. i still would love your input!

http://www.peachparts.com/shopforum/showthread.php?threadid=62294