Adding variable delay wipers to a W123

[VT220D]

The the stock delay wipers on the W123 have a single fixed interval. Often times I found myself wishing for a variable delay of the type found in many modern cars.

However, I didn't want to drill any holes for a delay control so I just lived with it. In an old thread about retrofitting "tap to pass" (Komfort Blinkers) several folks mentioned the lack of variable delay and proposed some custom solutions but the thread died. Fear not - there is a way!

Just like the Komfort Blinker mod VW provides the answer in the form of the 99 relay. This relay adds a variable delay to the factory stalk without any modifications.

With a 99 relay installed the delay position will work as before with a fixed interval similar in length to the Mercedes factory interval. However, the interval can also be user programmed! Simply turn the switch to delay and turn it off again before the wipe is completed. Once the desired time has passed just turn the switch back to delay and the new interval is set. A delay from a fraction of a second to about 30 seconds can be set.

Once the wipers are turned off (for longer than the programming interval) and on again the standard fixed interval resumes. So you can program it if you like or leave it alone. The great thing about this system is how intuitive is. Turn the wiper switch to delay, turn it off again, wait until you want it to wipe again then turn it back to delay. Most cars have an adjustment ring that takes several cycles to get just right. With this system the delay is determined by direct visual feedback. All other stalk functions remain the same. I've been using it happily on an 85 300D for several months.

The 99 relay is found in many late 90's Jettas. It can be found in other VW cars of that era too but the higher spec Jettas often have them. They are located on a relay panel under the steering column and are clearly marked "99" on top. I went to a local salvage yard and came home with 4 relays and sockets. Some cars have a socket block while others have removable single sockets. Sockets can be found in many VW/Audi cars even those without a 99 relay just take note of the pin configuration needed for the 99. VW uses many similar relays with subtle differences in pin orientation and size. Sockets can be re pinned provided they have the correct basic configuration.

The sockets are necessary because the 99 relay uses spade connector rather than pins. Aside from that it will directly replace the W123 delay relay (impulsgeber) without any mods to the basic wiring of the car. If you can solder, you can make an adapter using the 99 relay socket and pigtail with a salvaged Mercedes 6 pin connector. You don't have to hack the harness and you can always return to the stock configuration.

The delay relay on the W123 is located behind and to the left of the instrument cluster. It's possible to remove the relay and install the adapter by removing just the under dash panel but removing the instrument cluster will make the job easier.

The wiring for the adapter is as follows:

Mercedes Circuit # / VW circuit #

31 / 31
15 / 15
86 / T
J / I
31b / 53S
S / 53M

The circuit numbers are printed on the relays themselves.

This mod should work on several Mercedes models but as yet I've only tested the W123.

[Rick76]

Thanks for the write-up.
I'll be adding 99 relays and sockets to next weeks trip to the bone yard.

I was also thinking of adding the afterwipe feature that Saab had to get that bit of WW fluid or water that runs down the window after you shut the wipers off.

[disqo]

There used to be a forum member who made an infinitely variable wiper relay. His name was techguy512, but I don't think he is around anymore. I bought one and love it. I should have bought two...


Sent from my iPhone using Tapatalk

[ThatOne]

Originally Posted by disqo

There used to be a forum member who made an infinitely variable wiper relay. His name was techguy512, but I don't think he is around anymore. I bought one and love it. I should have bought two...


Sent from my iPhone using Tapatalk

Yes, he also developed and made available an enhanced function digital replacement for the tach amplifier used in later 123 and 126 diesels.

Designing a Better Tach Amp

[Rogviler]

Nice, might have to do that. My first car, an '84 Mercury Marquis, had a very nice variable delay function and I've missed it on every other car I've owned.

Of course if I'd known at the time that it was basically a 4-door Mustang I probably would have kept it, but that's a whole other discussion.

-Rog

[jay_bob]

I just compared the 123 and 124 wiper circuits, they appear to be arranged the same. Unfortunately the interval wiper relay is rolled into a common package with the turn signal flasher and rear defrost timer relay (device N10). Next time I am at the JY I will grab an N10 and a VW relay and see if the guts will swap over inside the N10 package.

Unfortunately no such luck in the 210, the wiper is run from the front SAM and the wiper switch in the stalk just puts different resistances on a control line to the SAM depending on the switch position. Although I may try to retrofit an IR rain sensor if I happen to come across a JY car that has it. The ML has the rain sensor and it is amazing.

[sixto]

Someone PM me if you have a spare relay to sell. Thanks!

Sixto
83 300SD

[jay_bob]

Originally Posted by jay_bob

Next time I am at the JY I will grab an N10 and a VW relay and see if the guts will swap over inside the N10 package.

Well I went to the JY a couple weekends ago and found two N10s from a Gen 2 126 and a 124. But no luck on the VW 99 relays, they were gone from the several VWs in the yard. Must be popular!

[Rick76]

Originally Posted by jay_bob

Well I went to the JY a couple weekends ago and found two N10s from a Gen 2 126 and a 124. But no luck on the VW 99 relays, they were gone from the several VWs in the yard. Must be popular!

What year Jetta were you looking at?
I picked one out of a '94. A '97 didn't have one.

I'm in the process of adding the 99 relay to a W124. I've removed the relay in the N10 MB module and other components that go to the wiper related pins (few diodes and resistors). I could not find room to fit the VW relay in the W124 relay center so I'm going to mount it below connected with 2 sets of wires with inline 3 way connectors. 6 wires will come out of the N10 module. I'm doing it this way so I can easily switch back to the original MB module if need be.

[funola]

I have a 92 VW idi Jetta and pretty certain there is a 99 relay but never knew this programmable feature. I'd have to try it out and see if it works. I also have one or more spare 99 relay in my stash.

Did some googling and found this on tdiclub forum 99 Relay mod (programmable wiper) - TDIClub Forums with a pic of said relay showing p/n. Searched for the p/n and found it can be had for as little as $7 https://www.*******.com/products?keywords=1HM955531

Not sure if that is the same relay but worth a try.

[funola]

Originally Posted by funola

I have a 92 VW idi Jetta and pretty certain there is a 99 relay but never knew this programmable feature. I'd have to try it out and see if it works. I also have one or more spare 99 relay in my stash.

Did some googling and found this on tdiclub forum 99 Relay mod (programmable wiper) - TDIClub Forums with a pic of said relay showing p/n. Searched for the p/n and found it can be had for as little as $7 https://www.*******.com/products?keywords=1HM955531

Not sure if that is the same relay but worth a try.

The programmable feature does not work in my 92 Jetta (it's fixed intermittent interval). It could be my relay is not fully functional or it does not have programmable delay. I missed the "A" suffice in the p/n in the pic of relay and there may be a difference. One has 5 pins and the other has 6. Not sure which is which and which is the programmable one. I have not pulled the relay in my Jetta to check p/n. Before buying the relay I linked to, I'd suggest verifying if it is programmable first.

[Rick76]

My '92 Jetta does not have the programmable relay. It has a number 19 (fixed time interval) but I tried the 99 in it and it works great. I guess I'll be looking for more relays at the wrecker.

[funola]

Originally Posted by Rick76

My '92 Jetta does not have the programmable relay. It has a number 19 (fixed time interval) but I tried the 99 in it and it works great. I guess I'll be looking for more relays at the wrecker.

Good to know. Do you have a p/n of the 99 relay? Do you know if a new aftermarket programmable delay relay will be marked "99" or just the 9 digit p/n? I looked in my VW Bentley and could not find the designation "99" on the wiper relay anywhere in the manual
.
Is your 92 a diesel?

[Rick76]

My relay 99 is part number is 357 955 531.
My '92 is gas.

[greazzer]

The Seller had a web page for these. I think I visited it a year or two ago. Not sure if he is still selling them. Since the Seller already went through the hassle to make these commercially available, it might be a good idea to see whether or not they are still 'for sale' ... or at least determine if he stopped selling them altogether...