Hello,

Odd question, but it seems that my ignition switch is really hot from time to time. I can't figure out a.reason for why it is hot when it is, sometimes it's when I am driving, other times its when I am just sitting with the radio on, and on ACC. Anyone have any experience with this?

I'd say it gets up to about 115-120 degrees F.

__________________
---------------------------------------------------------------

1998 VW Cabrio
2001 Audi SomeRoad A/T (no air suspension)
2003 Audi DeadRoad M/T (no vroom, for later)
2002 Audi NoRoad A/T (nothing under the hood, being rebuilt)

Pretty common in the Lucas world, but I've never seen it with a Merc. The ignition switch carries the load of most of the switched circuits. For those circuits with high current requirements, there will be a relay to relieve some of the load so the switch only has to power the relay.

This is problem could be internal to the switch itself, or it could be caused by a problem in one of the switched circuits. If it's intermittent, it's probably a downstream circuit rather than the switch. Where I would begin is by taking out the fuses, cleaning the fuse box contacts with a contact cleaner like Deoxit and a q-tip, and replacing them with new copper/ceramic fuses. Also remove each relay, clean the contacts, and replace. If that doesn't clear the problem, then you will have to go through the wiring chart, and test each switched circuit for high current draw, as well as testing the ignition switch itself for high resistance.

I have done Kent's recommendation here, all ceramic fuses, and I cleaned all the contacts with contact cleaner. I guess the only way To chase it down is through elimination, pulling each circuit until I find the cause...

Might spray contact cleaner on the contacts for the relays above the drivers' feet, see if that helps.

__________________
---------------------------------------------------------------

1998 VW Cabrio
2001 Audi SomeRoad A/T (no air suspension)
2003 Audi DeadRoad M/T (no vroom, for later)
2002 Audi NoRoad A/T (nothing under the hood, being rebuilt)

Over the years, contacts in all switches become "burned" from tiny arcs that occur when the switch is closed or (especially) opened. This creates what is called an "ohmic" contact, meaning the switch has a significant amount of resistance. This resistance causes a voltage drop and, multiplied by the amps going through the switch, tells you how many Watts of power are being dissipated in the switch. This wasted power (heat) causes the switch to get warm. Take the switch apart and clean the contacts or replace the switch.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Makes sense, thank you.. I'll have to see if there is a thread on how to do that specifically. On my phone just now.

__________________
---------------------------------------------------------------

1998 VW Cabrio
2001 Audi SomeRoad A/T (no air suspension)
2003 Audi DeadRoad M/T (no vroom, for later)
2002 Audi NoRoad A/T (nothing under the hood, being rebuilt)