Quote:
Originally Posted by 400HO F-BIRD
I like your suggested way to use a voltmeter to verify if this is the actual problem. The only thing is to know what is an acceptable voltage at the terminal. Is it 12 V, or maybe 11,5 V or what?
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Open-circuit voltage at the battery terminals should be 12.6--12.8 depending on the battery construction. I guess Absorbed Glass Mat (AGM) batteries tend to be on the higher end of that scale.
Under the heavy load of cranking the engine, voltage at the battery can drop to 9-ish volts, but higher voltage is better. A light load on the battery--the ignition system, starter solenoid, maybe brake lights--voltage at the battery might be 12.3--12.5, something like that.
So your voltage at the "S" terminal will be in relation to the voltage available at the battery (system voltage). I'd be uncomfortable with lower voltage than 1/4 volt below "system voltage" at the moment. 1/2 volt down is
probably excessive, 2 or 3 or 5 volts down from whatever the battery voltage is, is beyond excessive.
The BEST way to check this is via a "Voltage Drop" (VD) test. As you know, "VD" is to be avoided (or with electrical circuitry, minimized.) Connect voltmeter + lead to battery +. Connect voltmeter - lead to the "S" terminal, or to your extended "diagnostic" wire which is connected to the "S" terminal. Crank engine, (or at least turn key to "Crank") read voltmeter. Voltmeter shows the
difference between voltage at the battery vs. voltage at the "S" terminal. You'd expect a reading of ~1/4--1/2 volt when the key is turned, but I bet your vehicle has more VD, with higher voltage showing on the voltmeter.
Quote:
Originally Posted by 400HO F-BIRD
I've had already thought about installing a temporary wire from the S-terminal to the battery (without connecting it) to have as a back-up if I end up in the same situation again. That way I would both get home and know for sure that it is the original wire to the S-terminal that is the cause of the problem.
Do you think that could work?
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Absolutely...given that the additional wire has to be routed
and secured to avoid chafing/burning, or accidental contact with the battery; and that when connected to the battery +, it's going to crank the engine even if the car is in-gear, and even if the ignition is not turned on. If the ignition is on, the engine should start and run.
I've had two friends that had significant problems with vehicles that started because the neutral safety switch was bypassed. One got lucky, when the car took off, it "only" destroyed the bigass wheeled battery charger that was in front of the car. The other guy was injured. The wire you're considering will do the same as a bypassed neutral safety switch.