Engines dies when brakelight are activated

I have a 1978 Peugeot 103 with the coils inside the magneto.I got the bike running today and it runs and idles excellent until I apply the brakes then the engine dies.The headlight,tailight , brake light and the light switch all work fine.I installed new bulbs and swapped in new brakelight switches from a working 103.The brakelight bulb works and is not burned out, but like I stated earlier when I pull either brake handle then the engine cuts out.If I keep the rpm's tached up I can keep the engine running even when the brakelight is activated.All the lights and brakelight do work and work correctly but I guess something is shorting or /grounding out.How can I test and diagnose the lighting and ignitin coils? Also I have a wiring diagram from mopedriders .org but the wiring diagram is not the correct diagram for my application because the only wiring diagram that I could find is for a single rear tailight/brake light combo bulb and my bike has two seperate tail light and brakelight bulbs.Does anyone have the correct wiring diagram ( the two bulb type diagram for internal coils?).I have an audioble continuity tester and traced the tailight wires.The tailight that I have has four wires and looks like it is all factory wiring, the blue wire grounds to a bolt on the fender,there is a yellow wire which I guess is the switched 6volt feed,a black wire that goes to the magneto and a second black wire that that is grounded to the frame somewhere .Where should I start? How can I test the different compents while they are still on the bike? It would be nice to be able to check seperately the ignition coil ,light coil and condenser without having to unsolder and swap out out each component ! THANKS, PEUGEOT1

Re: Engines dies when brakelight are activated

probably: the brake light circuit is killing spark by grounding the spark circuit. I can picture the engine at high rpms continuing to run, but run badly.. Ignition sounds healthy and i don't suspect faulty components.

usually, a wire connects the condenser to the points.. this wire might branch off. It ususally branches to the kill (engine stop) switch and the key ignition switch. Both of these switches can kill the spark/ignition by grounding the ignition circuit.

Problem seems to be the brake circuit is somehow connected to the ignition circuit mentioned above.. activating the brake grounds and completes the brake light circuit and the brake light turns on, but it also incorrectly grounds the ignition.. so the engine dies.

With the key ignition ON, kill switch set to RUN and the brake engaged (ON), there should be no continuity between the brake wires and condenser wire .. you might check for that first. If there is continuity, the condenser wire is grounded and no spark...

perhaps a wrong connection.. or perhaps two wires with worn insulation side-by-side are making electrical contact... trace the brake light circuit wires, search for where they electrically join the ignition.

Re: Engines dies when brakelight are activated

Joew Two thumbs up for the lightning fast reply.Where can I get a wiring diagram?There is no key on my Peugeot, but I did put a new kill switch on my bike ,a switch from a 1980 Peugeot tsm but I totally disconnected the switch and I still experinced the same symptoms ...dies when brakes are applied. When I disconnect the brakelight switches and connect them together ,I Have no brakelight but the bike runs like new and starts with a mild single pedal kick.So you think a wire off the condenser might be shorting out? Do you have a wiring diagram THANKS PEUGEOT1 IN VIRGINIA

Re: Engines dies when brakelight are activated

i happen to be hangin around..

'totally' disconnectiing the kill switch means you yanked all the wires out and are positive there is no connection between them and the brake.. the wires matter as much as the switch.

After looking through the Resources- Links thing above, i see a couple of Peugeot manuals HERE that may help..

yeah.. i still do think the brake light circuit is somehow connected to the ignition .. run a continuity check .. ignition components seem to be just fine.

Re: Engines dies when brakelight are activated

Joew Thanks for your help I really appreciate this. Yes I installed the new switch with new electrical connectors that I can easily pull apart and disconnect.I downloaded the dot org diagram from the repair manual section but for some reason I can't download the the PDF acrobat reader and I let it download for four hours but I can't get the 103 owners manual to download it won't download and I don't know why ,can you get the owners manual or at least the wiring diagram part to download because I can't. A correct wiring diagram would be useful ,I have a wiring diagram for the single dual use tail/brake light model design but mine is a two bulb.The site you refer to has 3 Peugeot items, a repair manual, a dealer service manual and that owners manual that I can't seem to download.I can access the repair manual and I got that wiring diagram and I have several of the dealer service manuals(they don't have wiring info) but I need the correct wiring schematic. THANKS PEUGEOT1

Re: Engines dies when brakelight are activated

no sweat .. this thing is 7 Meg but only 12 pages.. probably just a very high resolution scan..

There's a wiring diagram on the last page so I captured it and made a jpg.. Quality is pretty close to original (crappy) PDF.. see attachment.. 75K

What you're interested is in the "Complementary wiring diagram in alternative with a tail stop light unit .. whatever.." on the right.

Dont ask me what they mean by "Reactance coil" .. i know what reactance is but never seen a coil anywhere near a light bulb.. they can't mean a choke coil found in radio equipment...


Re: Engines dies when brakelight are activated

I never seen anything like this and dont understand it... Since the brakes are directly wired into the ignition coil, a "choke" coil kinda makes sense..

If you're lost like me, see how the Rectifier also has a "reactance" unit thing in it's circuit? Find that, and you've probably found what's needed on the tail light circuit too..

anyway good luck with it..

Re: Engines dies when brakelight are activated

Electrical Peugeot wiring 101 class in now in session! What was Peugeot thinking .The more modern design 103...1980 and newer with external ignition coil and no rectifier or resistor seems to be a much improved designThe older system has a resistance coil under the back of the seat and there is a rectifier with 3 wires mounted on the frame right above the engine .The rectifier is a barrel shaped thing that looks similiar to a condenser and I am not sure how to properly test these two components but I guess I can try to swap them out from another working bike.Sometimes I don't like the swap out method of troubleshooting electrical parts because it is possible that what caused the original component to be damaged or fail might damage the components that are tempoarily swapped in for the test. Thanks ...to be continued PEUGEOT1

Re: Engines dies when brakelight are activated

JOEW ,Thanks for getting the wiring diagram of the ignition components I appreciate you doing that.Did you also download the other complete and total diagram you know the one that will show all the components lights, horn ,switches frame grounds I need that too? I definitely appreciate all your time helping me with this beast.I wonder why I can't download that owners manual?I can download the repair manual with no problem but when I try to download the 103 owners manual the whole screen freezes up as soon as it gets two page 2. I was able to get to page 3 once ,but then the screen and whole computer hangs up locks up...very weird.It wouldn't download when I had win98 ,and it wouldn't download with win2000....very weird! Did you have to log on or log in before you downloaded that jpeg? I have a slow dialup service but it still should have worked even if it takes an hour or two. ONCE AGAIN MANY THANKS Keep up the good work . PEUGEOT1

Re: Engines dies when brakelight are activated

I use Netscape.. click the pdf file link and the webpage tells Netscape to offer the choice: save to disk or Open in Acrobat. I chose Save and no problems.. 'cept its 7 meg.. but with DSL it took only a minute or two.

like i said, its only 12 pages.. The original seemed to be scanned as raw bitmaps (huge file size) .. I did a Print Screen of the .pdf page, opened in Paint, saved, and converted that bitmap to a jpg.

Im outta here for a while but i'll convert the other 11 pages to jpg when i get back.. I think i can shrink them into a small file that will work as an attachment here.. maybe zip or compress the thing too..

afaik, no log in required over in mopedriders.org, but i was already logged in here.. i dunno whats up..

i do know what it's like to not have a manual.. this one might have some useful bit of info..

Re: Engines dies when brakelight are activated

A rectifier is a diode or two.. Basically, it's job is to make sure current flows only one way.. its a one-way valve. AC flows both ways. Rectifiers change AC to DC while voltage drops somewhat..

When they fail, current flows in either direction..

Minimum voltage required to pass is around 0.6 Volts per diode in the series (this is why voltage drops).. A multimeter probably sends about 3 or 4 volts.. maybe 6 V when testing a diode or rectifier. Testing with a single 1.5 volt battery probably wont work.

A 3 wire rectifier probably has 2 internal diodes.. (half wave rectification.. splits and sends out in two directions)

picture it as a "Y" .. The leg of the "Y" is where current comes in (negative) and the arms of the "Y" have current flowing outwards (positive) to two differnt destinations..

Chances are you will see VERY high resistance (megaohms) in one direction and medium resistance in the other .. If so, teh rectifier is ok.. Your guess is as good as mine as far as which wire(s) is which.

Re: Engines dies when brakelight are activated

since im gonna be gone a couple days, wanted to get this up..

I missed this page while skimming the manual.. seems there are 24 pages , not 12.. 2 pages to a pdf "page".

here's the page with component hookups.. see attachment

got the manual in jpg format but its over 4 meg and i dont wanna post it here like this..


Re: Engines dies when brakelight are activated

My sachs has an automatic shutoff when you touch either brakes. this could be it. Its a sfatey measure so when you are using your front brake you don't fly over the handle bars.

Re: Engines dies when brakelight are activated

Don Pflueger /

no. its more likely that you have a bad brake light bulb, or a bad ground in the tail light assembly. no bike ive ever seen has any safety switches like you describe. and i've been building, riding, and racing bikes for about 30 years and worked in a honda dealership servicing bikes. the only thing that comes close to a safety switch is scooters where you have to squeeze the brake lever to start them.

Re: Engines dies when brakelight are activated


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