Key off, still running

[james64]

Volvo Penta AQ140A with points keeps running with key off. Replaced ballast resister and tested at 12.2 volts going in and 8.3 going out to coil. Still keeps running. Is there something else I could check?

 

[Scott Danforth]

welcome aboard

check the lead from the S-terminal on the starter. should not be power other than cranking

check the key switch to make sure its off (purple wire) (they do go bad)

 

[james64]

I will check out those tomorrow and get back to you, thanks.

 

[kenny nunez]

There is a diode that some alternators on Volvos have that when it goes out the symptom is what you are experiencing. It will be a short lead near the alternator with a spade connector that is used to excite the alternator regulator.

 

[james64]

I had replaced the ballast resistor with a 5 ohm resister because the other one fell apart. Checked switch and s terminals, all good. Maybe I should get a smaller ohm resister?

 

[alldodge]

Its not the resistor, could be your key switch has shorted out internally. The key supplies 12V to the resistor, so power is not being turned off, my guess its the key

 

[james64]

Power to resister cuts off with key. Unplugged wire from alternater to resister and motor dies with key, plug wire back on and it stays running with key off.

 

[james64]

With key on and not started, the resister has 10.4 volts going in and 8.4 volts coming out.

 

[alldodge]

Many of the later VP motors used diodes coming from the ALT to power the electric fuel pump. The AQ has a mechanical fuel pump unless someone did some changing.

Its hard to see but in the drawing, the wire coming from the ALT thru pin B (black wire) goes up to a light. The other side of the sight is 12V power coming from the key pin 75. So if the ALT stops producing power the bulb is turned ON by using the ALT as a ground.

Key pin 30 is main power to key, which comes from motor connector pin C (red wire). When key goes to ON, it supplies power to key pin 75 and 15. Key pin 15 supplies power thru motor connector pin D to the + side of coil.

http://162.144.28.33/lib/volvo/manuals/aq120b_140a.html#/48

 

[james64]

OK, I traced the wires. One purple wire from run position on key switch joins with another purple wire that goes to + side of coil and both wires connect to one end of resister. The other side of resister goes to alternator. When I unplug wire from alternator the engine cuts off with key switch. When I plugged the alternator wire back on the resister the engine keeps running when key is turned off. Makes no since to me. As stated above, the resister properties test good. It seems something is wrong with this wiring configuration. In present state, wouldn’t the coil have constant voltage from wire on key switch?

 

[james64]

FYI- The boat is a 1979 Yukon Delta 25’ 9” with AQ140A and dual sidedraft carbs.

 

[alldodge]

The other side of resister goes to alternator

This connection should not be there. The diagram above verify's it. A resistor will do nothing to stop voltage, it only reduces it.