Retrofitting an Electronic Flasher Relay

Written by Chris Blumenthal Friday, 30 September 2005 Retrofitting an Electronic Flasher Relay

By Chris Blumenthal

Introduction

Most 02 pilots have experienced turn signal problems. The dreaded indicator light "no-blinkie" and flash-only-once syndromes are among the most common. Another symptom is the fast-flashing indicator. Most of these problems seem to be traceable to excessive resistance in the turn signal/hazard flasher circuit. The '02 turn signal/hazard flasher circuit is notoriously sensitive to bad connections (both - and +) and poor quality bulbs causing too much resistance in the circuit.

About 6 months ago, my instrument panel turn signal indicator started working intermittently and finally got to the point where it would only flash once when I first applied the turn signal, even though both front and rear bulbs were flashing as appropriate. I went through my whole system, cleaning up the contacts and grounds, and replacing a couple of brass base bulbs with the supposedly preferable "silver" base bulbs (available from the dealer and aftermarket sources from manufacturers Sylvania/Osram or Philips [others?]). When this didn't fix the problem, I replaced the flasher relay. This fixed the indicator problem, but the flashing (both the indicator and bulbs) was about twice as fast as the original and normal speed... not quite as fast as when there is a burnt-out bulb, but way too fast. Reminded me of the turn indicators you see on the typical death car or '63 VW bus. This just wasn't right for a dignified '02.

The only direct replacement relays that I could find were marked "XS," with the X overlaying the S. It is my understanding that these relays are made by Siemens. A quality manufacturer for sure, but all of the OE relays I have seen were made by Hella. I have since tried a few different, used Hella relays lent by friends, but all have exhibited the original indicator blink-only-once problem. My conclusion: something beyond the normal and obvious is screwed up in my flasher circuit, probably in the wiring. I guess I could have lived with the fast flash problem, but it really bothered me.

The Solution

A few months ago, I happened across Zenon Holtz' web site. Zenon is an '02 brother from the Great White North (well, not so white in BC...) who has a nice BMW related web site, including a discussion (under "tech/troubleshooting turn signal problems") of using a generic, 3-prong turn signal relay in the '02. This got me thinking about using an electronic flasher unit in my '02. I knew from non-'02 related experience that electronic, variable load (resistance) flasher units are available for a pittance (<$5). Besides the low price, the other benefit of using for a generic electronic flasher relay is that external conditions do not determine flashing speed, which is electronically and internally regulated by the relay assembly. In fact, the "variable load" designation means that the flasher will function with different wattage bulbs, variations in circuit resistance, etc.

Get a 3 prong flasher unit with terminals marked "X," "P" and "L." There are different spec units available. Littlefuse makes a unit designated "EFL 300" that is appropriate- if you cross reference to that, you will get the right part. The X terminal is the +12V input, the P terminal output drives the flasher indicator in the instrument panel, and the L terminal drives the load (bulbs).

In the '02, the typical flasher wiring is comprised of a 4-wire circuit, including the following: brown (ground, of course), black/white (instrument panel flash indicator), green/violet (+12V) and green/yellow (load- bulbs). The brown ground wire is not used with the electronic flasher. The configuration of the male spade connectors on the flasher unit is very similar to a headlight connector. A female headlight connector with pigtails (available at most any auto parts store) works fine as an adaptor between the 3-prong electronic flasher unit and the '02 flasher connector. Note, however, that for a few bucks, many auto parts stores can provide a more precisely fitting plug intended specifically for turn sign flashers.

Just solder .25" male spade connectors to the pigtails (use shrinkwrap to cover your solder connections, of course) and plug into the '02 connector. Connect the "L" terminal to the green/yellow wire, "X" to the green/violet wire, and "P" to the black/white wire.

Conclusion

So, why do this? (1) Endless, cheap source of flasher units; (2) flasher is unaffected by and insensitive to slight variations in resistance in the old '02 wiring; and (3) nicely paced, perfectly timed flashing (again, regardless of slight variations in resistance in the circuit).

Although these flasher relays works with variable resistance, this setup will alert you to a burnt-out bulb by increased flashing speed like the original, non-variable load '02 flasher. Note: I am not advocating this as a solution for poorly maintained '02 flasher circuits. Use good bulbs, and keep your grounds, connectors and bulb contacts clean!

If you have any questions, feel free to post them to the Message Board!