Chrysler Repair: 1995 Chrysler Concorde, 1995 chrysler concorde, starter solenoid

Question
I own a 1995 (3.5,V-6)Chrysler Concorde.I recently started experiencing problems with the car not wanting to start at times.Sometime it starts right up ,then other times I may have to let it sit a while before trying again,or turn the key in the ignition and hold it for 2 -3 seconds and it sometimes kicks in.My fault codes read 12,21,and 77 and the check engine light comes on periodically,mostly while idling.Can you tell me what's wrong with this car?I think it may be the starter,or the ignition switch going bad.

Answer
Hi Stephen,
Assuming that the problem has to do with initiating the starter motor, rather than with the engine "catching" and idling, there are several possibilities. The starter relay is necessary to energize the electrical switch on the solenoid that actually applies the high current from the battery to motor windings. So it could be the motor brushes that carry the current, the solenoid itself, or the starter relay located under hood in the power distribution box.
The motor relay will only close if the ignition switch works, the gear shift is in park or neutral, and the relay is good. So I would, when the motor will not respond to the key, have a helper try the ignition key while you open the hood and check to hear the starter motor 'click' or not. If so then the ignition switch and gear shift safety switch are ok. If not, then a volt meter will be needed to determine which of the above switches is the problem.
If it does click, then it is possible that the internal switch points in the relay are oxidized, and again a volt meter applies to the brown wire at the starter motor solenoid will tell you if the relay points are conducting because the output of the relay is carried on that brown wire to the solenoid. Or you could buy a new relay if it isn't too costly. If the 12V appears at the brown wire at the starter solenoid and if the battery is fully charged, then either the starter solenoid or the motor brushes are bad...those are usually replaced with a rebuilt unit rather than sorting out which is at fault.
You might want to be sure that the battery voltage ia at least 14 volts as it sits, and also check that the fat red wire on the + post of the battery is connected firmly to the starter motor. But always disconnect the - post clamp from the battery so as to avoid shorting the battery when you examine the red wire as that would cause a large current pulse and a potential serious burn. Make sure the battery clamps are shiny as are the posts. Then apply a dab of battery post/clamp compound to the clamps and post and reconnect the battery, + post first, then - post.
The 21 code says that one (or both) of the oxygen sensors located one on each exhaust manifold is not working properly. The 12 code says the battery connection has been interrupted recently (check the clamps/posts, as above). The 77 says there is something wrong with the cruise control circuit.
Roland