1990 300TE electrical gremlins
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1990 300TE electrical gremlins
Hello folks. Have an interesting problem with the rear wipers on my 300TE. It began as a hard short when the rear wiper switch was moved to the on (toggle up) position. The intermittent setting would work. Now, the tail gate closing mechanism is making some odd noises, and not fully engaging the lock, and the rear wiper would not work in either position.
Then, the exterior lamp failure indicator came on, only when the brake pedal was applied. In doing some basic diags, I re-seated all the brake bulbs, and I noticed that the rear wiper would work. I then noticed that when I tested with the lift gate open, all the previous failures (with the exception of the wiper in the full on position) would work. I suspect that I've got a short in the wiring harness, but would appreciate any and all suggestions to confirm. Thanks. Chris
Then, the exterior lamp failure indicator came on, only when the brake pedal was applied. In doing some basic diags, I re-seated all the brake bulbs, and I noticed that the rear wiper would work. I then noticed that when I tested with the lift gate open, all the previous failures (with the exception of the wiper in the full on position) would work. I suspect that I've got a short in the wiring harness, but would appreciate any and all suggestions to confirm. Thanks. Chris
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From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
Your guess about the wiring harness is obviously right. To find out which circuit is causing all the trouble you have to pull the fuse, circuit by circuit and try to duplicate the failures. You have to very strict doing one step at a time only to circle in the failure source. It is a lot of work, especially Murphy's law applies here fully. Most of the time the last circuit you test is the devil. What you could do first, is take off the paneling of the rear door to see whether there are some obvious knicks or cuts in the wires and their insulation causing the weird functions. Did you ever check for any moisture or water in the rear door or light assemblies short circuiting wires? Good help would be to have the circuit diagrams on hand. Sorry I dont have copies to attach for the T-model. By the way, did never any fuse blow????
Good luck
Good luck
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Thanks bamberger_1.
Yes, I've taken off the rear panel. There are no obvious cuts or nicks on any of the wires. Also, there is no evidence of moisture in any of the areas. Tracing each circuit, as you suggest, is the next step. I suspect one of the wires has word hardened by the hinge point, and is making intermittent contact, which might explain why most of the circuits function near normal when the tail gate is in the full open position. Thanks.
Yes, I've taken off the rear panel. There are no obvious cuts or nicks on any of the wires. Also, there is no evidence of moisture in any of the areas. Tracing each circuit, as you suggest, is the next step. I suspect one of the wires has word hardened by the hinge point, and is making intermittent contact, which might explain why most of the circuits function near normal when the tail gate is in the full open position. Thanks.
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Finally got around to ordering a new lift gate wiring harness. When I removed the old one, I found at least three wires where the sheilding had come away, and one wire that was completely broken. The new harness has fixed most of the problems, but not all.
