Cheap flasher unit replacement

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Lock
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Cheap flasher unit replacement

Post by Lock » Tue Nov 19, 2019 10:25 pm

My original flasher unit finally died and I wasn't keen to pay the $150+ price of a new one, so I looked around and found the e28 unit has the same pinouts minus one, and can be had for $20 or so. The website for Werhle even lists the schematics and various models.
https://www.wehrle-electronics.com/en/t ... spx?LNG=en
It has the same 31, 49, 49a pinouts but is missing the "C" line. In our cars, this goes to the cluster indicator blinker, and the reason ours is so expensive is it has the smarts to blink just once when one of the bulbs is burnt out. I can live without that.
The e28s have a left and right dash indicators, so they don't need that line. How to make this one flash?
I used a bridge rectifier, taking input from the left and right indicators via the stalk plug making some Y cables because I don't like to cut the factory lines, removed the pins from the original flasher socket, and outputted the + side of the rectifier to the cluster indicator light.
I actually bought this particular bridge rectifier in a pinch on a road trip during summer when my AC compressor diode failed. Connected it up in the Frys parking lot and had much needed AC again.
Recently I also installed remote central locking installing the module in the drivers' door (there's power and it's easy to connect the master control and use the existing car wiring for all doors/trunk/gas cap), and used the 'impact sensor' line as output for the lock/unlock flashes. I found and clipped that line and hooked it into the - of the bridge rectifier. Be careful if you do this as there's multiple green/red wires, including power window supply lines. As they say measure twice cut once.
It now blinks on lock and unlock.
Per Mike W, the impact sensor is really a rollover sensor (thanks Mike), to unlock the doors in case of the car being upside down. I drive with my doors unlocked, besides its + signal isn't compatible with the standard negative triggered central locking systems.

Here's a picture and diagram to explain better. This might save some cash when your indicator flasher dies.

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1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

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Re: Cheap flasher unit replacement

Post by 528i-1981 » Wed Nov 20, 2019 5:34 am

I'm impressed by this but also I think the AC diode repair-in-the-Fry's-parking-lot is worth an explanation as well.
(oo=00=oo) Eric
1981 528i Manual

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Re: Cheap flasher unit replacement

Post by Lock » Wed Nov 20, 2019 9:23 pm

I actually found the pictures.. I was driving from the Bay Area to Reno in summer and always take tools for long trips.

It was pretty hot around Sacramento and the AC just stopped working, I found while the front fan was running, the compressor was not clicking on, and with my multimeter found the diode on the compressor connector line failed.

Found a Frys and scooped up a number of diodes and connectors and just dived in there in the parking lot. It's nice how the AFM/filter unit comes out in about 30 seconds. The bridge rectifier was easiest as it had tabs to quickly connect to. I've since soldered in another diode.

The car went fine the rest of the trip, no problems powering up the Sierra Nevadas.

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1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

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Re: Cheap flasher unit replacement

Post by tlake » Thu Nov 21, 2019 12:20 pm

Thank you for the excellent information Lock. BTW I have had that compressor diode die on me too. Concerning A/C, the condenser fan resistor is worth checking, and so too on very hot days the fuse coming apart from the holder in the fuse box. Concerning the holder there is a FAQ section on this site concerning this (fuse box) issue. :)

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Re: Cheap flasher unit replacement

Post by Lock » Sat Nov 23, 2019 12:48 am

Yes the First5 FAQs are still relevant today. Because of them I've checked and cleaned the contacts on the resistor for the fan, and also check if my fuses are getting hot when everything is running and clean the contacts every now and again.
These fuses aren't the best design but keep them clean and they should stay serviceable. I've been considering opening up the fusebox to see if there's contacts and joins inside it that might need to be re-soldered/sanded and cleaned, etc.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

tlake
Posts: 149
Joined: Wed Feb 03, 2010 6:33 pm
Location: WA

Re: Cheap flasher unit replacement

Post by tlake » Sat Nov 23, 2019 12:20 pm

Lock wrote:
Sat Nov 23, 2019 12:48 am
Yes the First5 FAQs are still relevant today. Because of them I've checked and cleaned the contacts on the resistor for the fan, and also check if my fuses are getting hot when everything is running and clean the contacts every now and again.
These fuses aren't the best design but keep them clean and they should stay serviceable. I've been considering opening up the fusebox to see if there's contacts and joins inside it that might need to be re-soldered/sanded and cleaned, etc.
Indeed, especially with age, and of course many cars bring the fuse box into the passenger compartment to avoid heat. (Volvo 240, Fiat 131 etc).

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