Re: how to test igniton/starter switch
Posted by HH56 On 2023/10/8 14:04:05
Power to BAT and use a volt meter between batttery ground and the other terminals. Key off, no other terminals hot. Key to left, only ACC hot. Key to right both ACC and IGN hot. Key to start and only IGN and STRT hot. Make sure the switch feels and moves smoothly between all positions and there is a good solid voltage at each position. Also make sure slightly moving, bumping or wiggling the key and switch does not make the reading start being erratic. You can also use an ohmmeter between BAT and the other terminals. In the same positions you should read a dead short going between the same terminals or at most a couple of ohms instead of a voltage. At any position, if you get a resistance reading of more than a couple of ohms suspect the switch might have a bad internal connection to a terminal. Same test with wiggling the key. Even the best of static tests will not be able to find a connection issue that only becomes apparent because of something in the switch heating up.
The issue with the switches mostly begins with the start contact. The large pinion shift solenoids used on senior models pull a lot of current which stresses the rather small start terminal in the switch to the point it pits and becomes rough or even melts. Once either happens the moving contact plate it and the other contacts rely on wants to stick or not move between positions. In that instance often the spring cannot return the moving contact to the run position when you let go of the key after the engine starts and starter hangs on and keeps running. The other issue with the switches is Packard started adding more of the heavier current needing accessories and the ACC contact started becoming overloaded. Overloading heats and warps the plastic contact support which brings up other issues and eventually the switch does not make reliable contact. That is often noticed when the key starts needing to be jiggled for the switch to work.
Here are a couple of photos showing the melted start contact and contact plate along with the active switch combinations.
Attach file:
terminals.jpg (67.55 KB)
ign sw copy.jpg (176.77 KB)
The issue with the switches mostly begins with the start contact. The large pinion shift solenoids used on senior models pull a lot of current which stresses the rather small start terminal in the switch to the point it pits and becomes rough or even melts. Once either happens the moving contact plate it and the other contacts rely on wants to stick or not move between positions. In that instance often the spring cannot return the moving contact to the run position when you let go of the key after the engine starts and starter hangs on and keeps running. The other issue with the switches is Packard started adding more of the heavier current needing accessories and the ACC contact started becoming overloaded. Overloading heats and warps the plastic contact support which brings up other issues and eventually the switch does not make reliable contact. That is often noticed when the key starts needing to be jiggled for the switch to work.
Here are a couple of photos showing the melted start contact and contact plate along with the active switch combinations.
Attach file:
terminals.jpg (67.55 KB)
ign sw copy.jpg (176.77 KB)
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