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#1
06-19-2020, 12:59 PM
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w140 Diesel Aux. Fan ON/OFF issues:
Yesterday I pulled out my dear diesel. I put on the AC to see how she was doing. In a minute or so she blowing cold. I went on a small cruise and had the thermostats set on 62 degrees . Cold condensation was forming on the lower windshield. AC was working great! Engine temp stays a tick over 80c. I came home shut her down and the low speed auxiliary fans stayed on with engine off and key removed. I figured it might have been hot so I left to go to the store for about 20 minutes.
When I returned the fans were still going. I looked around couldn't find any broken wires. I almost disconnected the battery,  when I went to the main fuse box near the firewall. I removed a 30 amp breaker and they turned off. This am I installed the breaker and they went on with no key again. Any one know where I should start? I read about Temp sensors going bad. But most of the posts were about gas W140s not diesels.
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#2
06-19-2020, 08:55 PM
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Cleaned up all the sensors, breaker with electric cleaner spray. The fans stayed on this am. Went out this eve reinstalled the circuit breaker and the fans never came on.
  The Merc Gods must have paid the old girl a visit  ...Thanks to them for the help.!
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#3
06-19-2020, 09:04 PM
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If there is a relay that drives the fans, it's possible that the relay has burnt contacts and is sticking when engaged. I don't know 140s, so just a guess.
__________________
Current stable: 1995 E320 157K (Nancy) 1983 500SL 125K (SLoL) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) Gone and wanting to forget: 1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]
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#4
06-20-2020, 08:33 PM
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Everything looked good. No signs of burnt anything....
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#5
06-20-2020, 08:46 PM
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Unless you took the relay apart, it's impossible to tell what condition the contacts are in. They're inside the relay itself. If they're fused together (which happens when they get old and wear out), they won't let go when the coil is de-energized.
__________________
Current stable: 1995 E320 157K (Nancy) 1983 500SL 125K (SLoL) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) Gone and wanting to forget: 1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]
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#7
06-21-2020, 09:38 AM
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I will look at it. After spray cleaning everything so far so good..
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#8
06-21-2020, 09:39 AM
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Are they in front of fans, part #s?
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