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Premium Member
1981 380SL
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36 Posts
Discussion Starter #1
After thinking that our 380sl was boiling... (it did once so we are hyper aware). Used to seeing the temp guage hover around 100, we noticed the temp creep up to 120, shut down motor, let it cool, then went straight home, next day car ran as normal temp about 90 deg, night saw the temp rise again. wife actually noticed that this happens only at night. got to experimenting with lights on during the daylight, result temp gauage goes high and it looks like the fuel guage is also affected.
Not sure if the guages are affected by headlight, battery voltage lowering or instrument lighting, maybe a faulty earth from the panel.

Anyone got any ideas....:confused:?

Trevor
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,322 Posts
After thinking that our 380sl was boiling... (it did once so we are hyper aware). Used to seeing the temp guage hover around 100, we noticed the temp creep up to 120, shut down motor, let it cool, then went straight home, next day car ran as normal temp about 90 deg, night saw the temp rise again. wife actually noticed that this happens only at night. got to experimenting with lights on during the daylight, result temp gauage goes high and it looks like the fuel guage is also affected.
Not sure if the guages are affected by headlight, battery voltage lowering or instrument lighting, maybe a faulty earth from the panel.

Anyone got any ideas....:confused:?

Trevor
Well, if you haven't done it already I suggest you run a ground from the cluster to some frame work under the dash. This always seems to solve gremlins.
 

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Premium Member
2010 Mercury Milan Hybrid, 1993 BMW 325i convertible
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6,077 Posts
You should also be aware that the gauge may show warmer in cooler weather than it does in hot weather. Mine does. I've got an idea why this might be the case, but I'm not sure.

I got an infrared thermometer from work - it's one of the touchless kind, that just shows the temperature of whatever you point it at. During cooler weather, my radiator temperature, and the temperature of the housing where the car's thermostat goes, stays just below the temperature where it's supposed to open. I'm guessing that the cooling system in my car works well enough that the thermostat doesn't open fully when the weather is cool, which restricts the coolant flow and makes the back of the engine block (where the temperature gauge sending unit is) warmer than it is when the thermostat is fully open, and the coolant is moving freely. The temperature of my radiator and thermostat housing was about 160F, while the temperature back where the sending unit is was about 195F. I've also measured it on warmer days and the two places are within 5 degrees of each other, usually around 180F.
 
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