Up until today all my guages were working correctly. I noticed that one of my turn indicators on the dash was not working so I took the dash out and replaced the light. after that all my guages are not working. The fuel guage that previously read empty now reads full. The pressure guage thatconstantly reads 3 bar is intemitant and will read 1 to 3 at any point in time regardless of RPM and temp from cold will pulse at idle until it gets to 120C in a matter of 5 minutes at idle. I can only assume that this is an electronic issue as this all happened in one day and only after I took the dash out. Is there an amp that controls these guys. I know that the guages work of resistance and that resistance is shown through the guage. What could this possibly be. I took the dash out again to see if i didn't plug something in but everything looked fine. suggestions???

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68 250s SOLD
78 300d non turbo SOLD
1980 240d manual SOLD
1981 300SD 360,000 miles I think she's doomed for a parts car but has a good engine SOLD the engine to spamman
1977 300d non turbo SOLD
1985 300SD california car
1978 240D Manual

Go back to the basics . Check all fuses and fuse connects and grounds. I had a similar problem on my 1983 300SD is it was just a corrosion on a fuse connection .

replace the fuse(es) even if it looks good

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1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins

I checked the fuses and it is fine. After checking the fuse I noticed that the oil pressure and the temp guages pulse to the tick of the clock. I then removed the fuse for the clock to see what it would do. When I rev the engine both guages move to the RPM of the engine i.e. when rpm is low the guages read 1-2 bar and 40C and when the RPM are high they read 3 bar and 120C. I know there is a short somewhere. what should I look at first?

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68 250s SOLD
78 300d non turbo SOLD
1980 240d manual SOLD
1981 300SD 360,000 miles I think she's doomed for a parts car but has a good engine SOLD the engine to spamman
1977 300d non turbo SOLD
1985 300SD california car
1978 240D Manual

replace fuse 12

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

I have already ruled that out as the fuse is fine and the guages pulse to the tick of the clock or the intensity of the RPM.

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68 250s SOLD
78 300d non turbo SOLD
1980 240d manual SOLD
1981 300SD 360,000 miles I think she's doomed for a parts car but has a good engine SOLD the engine to spamman
1977 300d non turbo SOLD
1985 300SD california car
1978 240D Manual

If it pulses/works intermittedly it could be a grounding issue.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

I'm also betting you have a loose ground. I would check the grounds directly behind the instrument cluster first as that is where you worked last.

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Sam

84 300SD 350K+ miles ( Blue Belle )

I will check to see if I have a lose ground but the guages seem to work with the clock and tach which work fine. the guages work off resistance the more the resistance the less the guage reads. the guages read full, 3 bar and 120C.

__________________
68 250s SOLD
78 300d non turbo SOLD
1980 240d manual SOLD
1981 300SD 360,000 miles I think she's doomed for a parts car but has a good engine SOLD the engine to spamman
1977 300d non turbo SOLD
1985 300SD california car
1978 240D Manual

So I noticed that the insturment cluster gets ground from a thin piece of alluminum that runs from the cluster past the odometer and speedometer to the tach. when I give ground to the piece of metal all the guages from the cluster work. I noticed that there is no ground wires or anything that would give me ground on the tach and clock side. However all the lights and tach and clock work. When i have ground to the guages, and turn on my high beams the guages go haywire and the seatbelt warning buzzer goes off.
First off I want to know how the tach and clock get ground and which way it is flowing(from the guage cluster to the tach or visa versa.) second this sounds like more than just a ground issue as the hibeams are making the guages not work even with ground to them......I hate electricity!!!

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68 250s SOLD
78 300d non turbo SOLD
1980 240d manual SOLD
1981 300SD 360,000 miles I think she's doomed for a parts car but has a good engine SOLD the engine to spamman
1977 300d non turbo SOLD
1985 300SD california car
1978 240D Manual

Well, first off the electrical systems on this car are very basic. Most indicators consist of power, ground and a sensor input (resistance). There are other areas to check for grounding such as battery-chassis and chassis-engine. Either one of these can give not only strange indicator problems but also starting problems which are very intermittent. IIRC there are about 3-4 grounding points behind the instrument cluster.

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Sam

84 300SD 350K+ miles ( Blue Belle )

What is IIRC and exactly where are the ground points? That is what I was confused about is that i notice on the clock side there are a couple of lights (antilock breaks and seat belt indicator that work fine without me giving ground to them, but when I give extra ground to the backing that the bulbs are plugged into...the guages on the other side work. so I guess that tells me that the guages are not getting enough ground on the guage cluster side, however that does not explain how the guages go haywire when I turn my hi beams on. I noticed that there is raw metal behind the dash where it sits that I can get ground from. I thought that might provide ground but everything around the instrument cluster seems to be insulated.

__________________
68 250s SOLD
78 300d non turbo SOLD
1980 240d manual SOLD
1981 300SD 360,000 miles I think she's doomed for a parts car but has a good engine SOLD the engine to spamman
1977 300d non turbo SOLD
1985 300SD california car
1978 240D Manual

IIRC = If I Recall Correctly

The ground points behind the instrument clusters are terminals attached to the chassis with screws.

A failed ground can give all kinds of symptoms including haywire guages when you turn the headlights on. What happens is different systems try to "find" a ground through other systems. A ground is half the circuit and frequently overlooked by folks unfamiliar with electrics.

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Sam

84 300SD 350K+ miles ( Blue Belle )