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Posted By Discussion Topic: solenoid test     40guy 07-07-2011 @ 3:21 PM reply profile send p.m. Member Posts: 270 Joined: Oct 2009 How do I bench test a starter solonoid {1940} with a ohm meter and what should the readings be? I got 1.7 to 2.4 but am not sure if i"m doing it right. supereal 07-07-2011 @ 4:31 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 If the solenoid has two small terminals, put the ohmmeter across those and see if the circuit is complete. If not, the relay coil is open. If you.have only one small terminal, check between the terminal and the mounting bracket. If the relay pulls, check between the large terminals to see if the points close. 40guy 07-07-2011 @ 5:25 PM reply profile send p.m. Member Posts: 270 Joined: Oct 2009 Thank you Supereal. I performed the test and here's what I got. The solenoid has one small post. My ohm meter is set at 20K. The meter reads 1 . without touching anything. Touch snall post and bracket, no change. Small post and battery side 0.00 reading. Small post and starter side 1 . reading. So; what does all this mean? supereal 07-07-2011 @ 8:48 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 You should set your ohmmeter at the low ohms position X1. if you get no continuity between the small terminal and the battery post of the solenoid, the relay coil is open. With the single small terminal, the relay coil is connected internally to the battery post, and receives ground thru the starter button. The reading in ohms is not important. You are looking to see if the relay coil is intact. From your readings, it appears the solenoid is defective. To confirm this connect one side of a battery to the small terminal, and the other to the large battery post. You should be able to hear the solenoid operate as you do this. As mentioned earlier, there are several configurations of solenoids. Old Fords with one small terminals use the internal connection to power the relay, while other makes use the bracket for ground, and provide power thru the starter button. They don't interchange, so you have to be sure which one you have. TomO 07-08-2011 @ 8:10 AM reply profile send p.m. Senior Posts: 7276 Joined: Oct 2009 Bob, check his readings again. He said his ohm meter read 0 ohms when connected to the small terminal and the battery post. This indicates that the coil is good. The ohm meter should be set at the lowest scale (R x 1) to check the coil. Another way to check the coil on the single post solenoid is to measure the voltage between the post and ground with 6 volts connected to the battery side of the solenoid. There should be 6 volts there. Due to the high current draw of the starter, it is best to do check the internal contacts under load, by measuring the voltage drop across the solenoid while the starter is engaged. .003 ohms can cause a .6 volt drop across the solenoid and that is excessive. The final test of a solenoid is will it activate and are the internal contacts good. A solenoid can have a good coil and not activate due to mechanical problems, or poor grounding when installed. The internal contacts and cables should not drop more than .3 volts when the starter is operating. This voltage is measured with the NEG meter lead connected at the battery post and the POS meter lead connected at the starter motor terminal and includes resistance in the cables and their connections. Tom This message was edited by TomO on 7-8-11 @ 8:22 AM supereal 07-08-2011 @ 10:46 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Tom: I took his explanation to mean he got no reading at all when he said "zero". He mentioned he was on the high scale and I, too, suggested he go to the "X1" setting, as the 20K setting will show a reading just by touching the leads. He should be able to hear the relay pulling if he puts a battery between the battery pole and the relay terminal, anyway, and if the solenoid is good, they will usually jump on the bench, as you know. I've seen very few defective solenoids over the years, as long as they are correct for the system voltage. A 6 volt unit in a 12 volt car usually pops the coil, and the reverse means a "buzz" at best. He didn't say whether he was using an analog or digital meter, either. A cheap analog meter should be in evryone's tool kit. I use mine more often than the pricey Fluke digital meter in our shop, except on modern vehicles where micro amps and volts are present. supereal 07-09-2011 @ 10:10 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 After rereading the initial question, I believe that the problem with a solenoid not seeming to work is the result of having swapped the battery and starter cables at the unit. He says he got a reading between the starter side and the small teminal. There should be no reading between the small terminal and the starter side, only the battery side. I've seen that more than once, as the cables were installed in what looks like a tidier position, but it deprives the relay coil of power, making the solenoid inactive. A lot of solenoids, and even starters, were changed because of that error.

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