Testing a Solenoid
 

How is a stater solenoid tested? I want to find out if the solenoid is good or on the edge of failing.

The only safe way to test is is to remove it from the engine. The starter will "kick" when it is engaged so either mount it in a vise or secure it in some fashion. Connect a 12 volt positive lead to the starter positive terminal and a grounding strap to the body of the starter. Use a 12 volt jumper wire an touch it to the small terminal on the solenoid. You might have two small terminals on the solenoid so if one doesn't engage the starter try the other.

Don't know why you'd go through all the trouble to test it when it's less labor time to simply replace it.

Generally the Bosch solenoids work until they fail. Sneaky SOB's rarely give any warning.

http://www.peachparts.com/shopforum/diesel-discussion/393428-expert-starter-solenoid.html

See #15.

Be aware that if the starter brushes are failing, the solenoid will not pull in. This is because the pull in coil is " grounded " through the starter motor. The hold in winding is grounded to the case however.

Are you having some sort of improper operation? If so, what are the symptoms?

There ya go! More info than you'd expected. The members of this forum are sure a handy bunch to know.

The funny thing is that no one has yet to answer the question. How was Bosch able to bench test their solenoids? I would like to determine if the solenoid on my starter needs to be replaced or not.

It is not funny at all. Remove the solenoid and Post #3 will show you EXACTLY how to bench test the solenoid. It is a double solenoid with a pull and hold solenoid in there. No one is going to hold your hands here.

What are the exact perimeters that Bosch uses to determine if a solenoid passes quality standards at the time of of manufacture and do not tell me that the pass or fail standards at Bosch are that it turns on or does not. I am looking for very exact information.
I had already bench tested the motor and the solenoid before asking this question. I know that everything works. I want to how long it will last. I want to know how to determine the life span of the solenoid. Not just that it works or not.
Oh and by the way I do not need my hands held. Thank you very much.

You could contact Bosch however, I doubt they would give this info out ( or even have it handy. ) .

It is very likely the Bosch manufacturing test for most of this coming off the line is " works or not ", with a few pulled for more extensive testing.

Do you have a sense of what characteristics you are looking for?

What quantitative tests have you performed on the starter motor? This would give me some sense of what test equipment you have and how it can be applied to the solenoid testing.

It is very difficult to determine how much longer your specific solenoid will last unless you have records of number of crank cycles , length of each crank cycle and amperage draw for the solenoid coil and starter motor . You will also need statistical data from other failures to determine MTBF and where on the curve your solenoid lies.

. . I hold the truths to be self evident. . .

You are asking a question for which there is no absolute answer. If you are half as experienced as you make yourself out to be, you already know that manufacturers spend untold amounts of time and money trying to determine the expected lives of their products in various environments and uses. Regardless of the results of this testing and the average values obtained, many units last far longer than would be expected and some fail after very few cycles.

Just as a Magnaflux test will tell you that a part is not presently cracked, it does not tell you that it will not crack tomorrow. There is simply no way to predict how long any individual unit will last. If you are worried about your solenoid, replace it, but there is no guarantee that the replacement part is any better than what you have or that it will last any longer. Actually, given the quality of electrical parts today and the number of failures encountered right out of the box you might be better served by sticking with what you have.

As mentioned above, only Bosch knows what the *Exact* parameters are for a test. Likely winding impedance, winding insulation resistance, and whether or not "it turns on or does not".

Solenoids are pretty simple. They work or they don't. There isn't much else to test.

Yea thats what I thought the answer would be. Sorry but I made the mistake of not framing the question in better detail. Which brought about a lot of answers which I already knew.
I had already spoken with a starter repair company. They said that it was almost impossible to predict when a solenoid would fail which is what I already suspected.
I am not 100% sure about the this starter. I can tell that it has been rebuilt but the solenoid is probably original. At 50 years old I have doubts about the longevity and performance of it. It is the lack of history with this car that has caused many a problem for me. This being my second full restoration of a 60s era Mercedes. I have learned that it is better to just rebuilt or replaced almost everything.
My goal was to find out if there were a way to measure the performance of the solenoid and find out if it was still within the specifications for optimum performance. I am sure these specifications exist. But is the equipment available to actually measure it and will Bosch supply and the specifications?
I am tempted to purchase a new solenoid and install it on the starter but I do have another starter which I may put into the car. I know the history of this starter as opposed to the one I took out of the car.
And yes I do know a lot about these cars but my Achilles' heel of auto restoration is the electrical systems. I have the damnedest time trying to figure it out or more accurately remembering how everything works electrically.
I think everyone and I appreciate all of your answers.
Take Care

Let me hold your hands one more time.

1) solenoid works or doesn't work. It is only a coil and the MTBF is in the million.
2) there is a big metal contact inside to shunt the 12v to the starter motor. They can be pitted and don't make good contact. Starter/engine motor will not turn as a result.
3) the starter motor winding plus the carbon brushes are in series of the pull solenoid. If they are not in good shape then the solenod will not pulled and shunt the big contact. So no click noise. No starter/engine turn.

Good luck.

Let me make extra comments.

a) If you don't hear the solenoid click ( pull solenoid working ) then it could be the pull solenoid or the starter motor winding/carbon brushes. The winding and the brushes are in SERIES with the pull solenoid. That is why sometimes you hammer on the starter motor and it will work. It is because the carbon brushes is on a dead spot on the winding armature.
b) If you hear a click but no turn then it could be the BIG contact pitted inside the solenoid or the starter motor winding/carbon brushes faulty.
c) Solenoid and start motor are interdependent and is difficult to be 100% sure which one is at fault.

If you have ANY reservations about the quality or condition of the solenoid, replace it. It's an inexpensive part, and the time to replace it is when the starter is removed from the vehicle. The solenoid itself very rarely fails, it's usually the switch contacts that fail (hence the clunk, but no start condition). It's impossible to inspect the switch contacts, the course of action is replacement.

Gee, nothing like being clueless about electrical parts then getting belligerent with those that actually know how things work.