Question
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Followup To
Question -
Completely Stock 1959 Ford Fairlane 500...In driving this car,with the lights on, coming to a stop, kills the engine every time you put the brakes on...My Son has replaced the ignition switch, light switch, checked front and rear lights for shorts..nothing helps?
Answer -
I need some more information:
What transmission does the car have, and which engine. Does the car have power brakes? Does the car still have the original type bulbs in the brake lights (1034 or 1157 bulbs)?
When the engine stalls, does it appear to be because the idle speed drops so low that it cannot keep turning, or does it appear that the ignition voltage goes too low to produce a spark? If you don't know the answer to that, get a test light from your auto parts store, and monitor the + terminal of the ignition coil while you try to reproduce the problem. The test light should flutter rapidly with the engine running at idle - that's normal. What I need to know is what does it do when the engine dies with your foot on the brake pedal. Does the light go out completely, or does it stay on, glowing dimly? If the former, does it come back on when you release the brake pedal?
When the ignition switch was replaced, was it for this reason, or was there some other reason to replace it? (The reason I ask is that one possible cause is an error in wiring the ignition switch, but if it was doing this with the original, undisturbed factory wiring, that is eliminated as a possiblity).
Give me the answers to those questions and I'll try to lead you to the culprit. Engine: 292 V8. Trans:Auto 2speed. ignition switch replaced for this problem, light goes out, stepping on brakes, no problem with lights OFF! Original bulbs all around...No power brakes....
Dick
AnswerOK, that narrows down the field of possiblities considerably - thank you.
There is definitely a wiring problem, but I'm not sure yet which wire is involved.
To track down the problem, we'll have to do some more fiddling. First, take both wires off the brake light switch - just let them hang loose without touching anything for the moment. Now try steping on the brake to see if it STILL kills the engine.
If it DOES, there is a wire rubbing on the brake pedal operated moving parts which must have a bare spot, and is shorting the ignition feed to the ballast resistor and coil circuit to ground. You are going to have to slither under the dash to find the culprit. Try not to move anything before you find it, because if you move the wires even slightly, the problem will probably go away, but it will come back later. When you find the bare wire, tape it up securely with electrical tape, and also move it and secure it so that it cannot contact any metal parts.
Ok, back to my 3rd sentence again:
If stepping on the brake does NOT kill the engine with the switch disconnected (which I assume will be the case), my guess is that the feed wire to the brake light switch is coming from the wrong terminal on the fuse block. To investigate this, use your test light to probe the two wires that WERE connected to the brake light switch. One of those wires will have 12 volts when you are NOT stepping on the brake pedal - identify that wire, and try to trace it back to where it comes from. It should come from a circuit that is live all the time, not one that is connected to the ignition system. To prove this, temporarily replace this wire with a substitute wire from the same terminal on the brake light switch directly to the car's battery + post. Now connect the other wire (the one which goes back to the brake light bulbs - the other one we disconnected from the switch.) Now the brake lights should operate normally, and should not affect the engine at all.
If this is the result, it only remains for you to install this replacement wire permanently - rather than running it to the battery + terminal, you can route it back to the brake light fuse holder, and connect it to that terminal ( the end of the fuse that has no 12 volts when the fuse is temporarily pulled out). Tape off the wire that caused the problem and forget it, if you cannot trace it back to where it came from.
I hope this is helpful - let me know, please!
Dick
Apparently, my first answer to this was lost in the system somewhere - I hope this one comes through OK - I'm tired of typing!
Dick
