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Old 23-08-2015, 19:11   #1
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Volvo MD7A starter wiring questions

Hi again!

Thanks for all the help I have been getting. The boat is slowly, but surely coming along.

I went to re-hook up my starter today and got confused. There is an extra "male" quick connect on the starter that I did not expect to see. I do not have a stray wire in the engine room that would attach to it (I also don't have a key switch, but that is for another post).

I just want to get the wiring right.

The MD7A Volvo Penta factory wiring diagram is wrong. It does not list the smaller horizontal quick connect at the bottom of the starter. I looked at aftermarket starters and don't see this "feature" on any of their starters. I have also looked at the schematics from Volvo's part's website to no avail.

There are three connections on the starter (please correct me if I am wrong).

#1) cable from battery lug (via battery switch)
#2) a vertical normal sized quick connect on the top of the starter--I think this is where the key switch activates the solenoid. Please correct me if I am wrong.
#3) (this is the confusing one) a horizontal smaller sized quick connect at the BOTTOM of the solenoid. Is this a ground? Any ideas?

Pics are included. All pics are from the back side of the starter.

Any ideas as to what each of these connections are for?
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Old 23-08-2015, 19:36   #2
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Re: Volvo MD7A starter wiring questions

It's 12v for accessories, like the coil on a gas engine. Older cars had a dropping resistor before the coil. When you engaged the starter the voltage drop in the system would be so much that with the resistor dropping it even more, the engine would not start. Why they couldn't have a coil that would operate on 12v is beyond me.
So it could be a solenoid from the past.
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Old 23-08-2015, 19:47   #3
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Re: Volvo MD7A starter wiring questions

Quote:
Originally Posted by Guy View Post
It's 12v for accessories, like the coil on a gas engine. Older cars had a dropping resistor before the coil. When you engaged the starter the voltage drop in the system would be so much that with the resistor dropping it even more, the engine would not start. Why they couldn't have a coil that would operate on 12v is beyond me.
So it could be a solenoid from the past.
Hmmm.

And is there any way to tell for sure if this is what it is? I have a 12v meter.
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Old 23-08-2015, 19:47   #4
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Re: Volvo MD7A starter wiring questions

To clarify:

The engine is a 1981ish 2-cylinder diesel Volvo.
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Old 23-08-2015, 19:54   #5
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Re: Volvo MD7A starter wiring questions

Sure. Solenoids are solenoids. You will have batt voltage while the starter is engaged. After you let off the key you will have no 12v volts at the terminal.
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Old 23-08-2015, 20:43   #6
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Re: Volvo MD7A starter wiring questions

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Sure. Solenoids are solenoids. You will have batt voltage while the starter is engaged. After you let off the key you will have no 12v volts at the terminal.
So when I hit the starter if I don't get any 12v coming out of that terminal then I know it is a ground?
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Old 23-08-2015, 21:09   #7
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Re: Volvo MD7A starter wiring questions

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So when I hit the starter if I don't get any 12v coming out of that terminal then I know it is a ground?
I don't think so. It should be open or very high resistance but I think you will get 12v. You don't need any ground down there.
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Old 23-08-2015, 21:32   #8
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Re: Volvo MD7A starter wiring questions

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I don't think so. It should be open or very high resistance but I think you will get 12v. You don't need any ground down there.
Got it. So if don't attach anything to that little terminal when first firing it up no harm, no foul correct?
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Old 23-08-2015, 21:59   #9
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Re: Volvo MD7A starter wiring questions

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Got it. So if don't attach anything to that little terminal when first firing it up no harm, no foul correct?
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Old 25-08-2015, 16:01   #10
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Re: Volvo MD7A starter wiring questions

a little off subject, but does only one have a wiring print for the tach hookup for a volvo md7a
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