Quote:
Originally Posted by Texasgeezer
To 87TDwagen,
Do you mount the window relays inside the door cavity?
Is there a single relay available to reverse the voltage for the motor?
Any brand of relay and model you've had good success with?
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I have usually installed them in the lower A or B pillars, where the wiring is before going into the doors. Usually there are kick panels in these areas to make access easier if needed. The goal is to use as much of the factory wiring but keeping the load side as short as possible to the motor. If your switch is on the door, then the relays should go in the door cavity, but in MB and most Euro cars of this era we are talking about center console mounted switches.
As to relays, you could get fancy and source a DPDT relay as a single relay to handle both directions, or use 2 single throw/pole relays one for each direction. I have a bunch of Bosch "Ice cube" relays, really old ones with the metal cover as shown below, but any will work. Those old Bosch ones are really reliable and very well built and I've probably only ever changed out a handful of them ever in 40 years of wrenching due to failure, plus these with the metal cover can be easily opened and serviced if needed. Available in 15,20,30Amp varieties.
You can pick what ever you are comfortable working with. I prefer the spade relays as they are far more common, and allow you to easily to wire in with regular spade connectors, or relay holders. The MB round tang relays would require obtaining specialized connectors which are harder to source.
As others have mentioned, cleaning window switch contacts for 1970-mid 80's to keep things working was and still is common practice to keep things working. Par for the course with these cars. Avoidable if you install the relays. A switch can only be disassembled so many times before it is destroyed from the process itself.
This mod came around namely thru Jaguar or any British car, enthusiasts, having to deal with Lucas "Prince of Darkness" electrics. I've done this to Series 1,2,& 3 cars, starting 25 years ago and have yet to experience a failure since.
I do not agree that you are introducing new failure points to the design. While theoretically you are adding more potential failure points, by correcting the original, most prevalent failure, current overload, you are reducing the overall failure of the system dramatically.
This mod is well documented, in this forum, and in many others, you can find schematics showing various ways to incorporate the relays on the interweb. You can also find more information in Kirby Palm's "The Book" on the Jaguar XJ-S which explains in detail the how to's. It is a mod that works, works well and is very reliable and has been applied by thousands of enthusiasts over the decades.
Hope that helps a little.