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Re: Starter Gremlins
Posted by Old Guy [Email] (more from Old Guy) on Mon, 27 Nov 2017 21:14:50
In Reply to: Re: Starter Gremlins, eric in vermont [Profile/Gallery]
, Mon, 27 Nov 2017 17:42:27
Eric in Vermont,
I've got 12-14 volts to the primary solenoid post, continuity between the chassis and the engine block via the primary grounding wire, and a functioning ignition circuit (12-14 volts when activated). What I also have (under the conditions described in the original post) is an energized engine block - in other words if I test for voltage between the chassis and engine block, I'm reading the same 12-14 volts.
When I say there is voltage across the post, I'm referring to the second smaller post that connects the solenoid to the starter. This post is directly connected to the ignition circuit via the solenoid windings and is what the internal tab of the solenoid connects to when the solenoid is activated and retracts. Normally, when the ignition switch is activated, power will run through the ignition wire connection, then through the coil wires (activating the coil and connecting the internal tab to the primary power at the main post while simultaneously extending the starter gear). The power then transfers via the wire on the smaller post to the starter motor coils, activating the starter, and is grounded on the far side of the starter brushes to the starter casing/engine block and returns to the battery.
Should the body of the solenoid also be connected to the smaller post? On both my original solenoid and my brand new replacement, this is the case, which seems odd to me. You mentioned the possibility of a shorted starter. I'm not sure how you check that as the starter is intentionally grounded to the casing (after the windings). Is it possible the culprit is rather a shorted solenoid?
Unless I'm missing something, the smaller post should never be powered unless the ignition switch has been activated. The fact that it is means that power is running backwards through the assembly so that when the ignition circuit is turned on it is effectively nulled because the circuit is already saturated.
It's not uncommon to damage electronic ignition circuits when troubleshooting, and I'm guessing that while the module creates a magnetic field, it should not be grounding to the distributor. I'm also guessing that I may have a bad/grounded temperature sensor. Both are relatively easily replaced. The alternator is a bit of a crap shoot. I've added a remanufactured unit from a later Saab 900 that has a higher output as I'm running double electric cooling fans, an AC unit and modern radio system. As a retrofit, it's possible I don't have the connection right for the charging trouble light. The new alternator has an internal voltage regulator. What still has me scratching my head, however, is with all three disconnected (and no voltage across the engine block) I'm still not getting any action out of the starter.
posted by 173.174....
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