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#1
06-09-2018, 09:51 PM
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what to do about hot relays?
84SD I was reinstalling the climate push button and sitting with both of the driver side doors open in 90* heat. The car wasn't running. I went to check fuses and noticed that relays A (seat control) and F (window relay) were both hot.
Heat in wiring usually means resistance. How do I systematically search to and remedy the cause? All circuits appear to work.
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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do. 
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#2
06-09-2018, 10:16 PM
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The power relays in the fuse box can get pretty hot. They have low resistance coils and dissipate a couple watts worth of heat when energized. The result is a hot can.
__________________
Current stable: 1995 E320 149K (Nancy) 1983 500SL 120K (SLoL) Black Sheep: 1985 524TD 167K (TotalDumpster™) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!)
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#3
06-09-2018, 11:44 PM
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Strange if you had not been actuating those relays. I don't know the SD. My 84 & 85 300D have relays only for AC and radiator fan (plus relays built into climate boxes). I assume you aren't talking about the relays on the climate push-button box. Normal Bosch 30 A relays don't get hot from the coil current, maybe slightly warm. If the contacts have too much resistance, they can get hot when flowing a lot of current, but that might mean they are about to die.
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1984 & 1985 CA 300D's 1964 & 65 Mopar's - Valiant, Dart, Newport 1996 & 2002 Chrysler minivans
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#4
06-10-2018, 06:55 PM
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The front windows in my w124 would work with no key in ignition as long as at least one front door was open , this is a standard feature. Possibly this may be the reason your window relay is hot ?
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#5
06-11-2018, 05:51 PM
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If relays get hot while in use, my experience is they are drawing too much current. This can be due an inductive load, such as an electric motor, starting to break down or bind or possibly a grounding problem.
However, if not in use, the relay itself may be breaking down, usually due to an internal diode.
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Sam 84 300SD 350K+ miles ( Blue Belle )
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