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Testing the master contactor

8

8 Builder

Active Member
I have an ES 24115 master contactor. I wanted to hear the contacts close when power was applied. I used a small 12 volt lead acid battery for the test. I hooked the positive lead of the battery to the contact labeled BAT. I then touched the negative lead of the battery to the small control terminal on the front of the master Contactor. The diode is in place and properly oriented. Connecting the negative lead to the control terminal resulted in what seemed like a direct short circuit. Lots of Sparks and heat from the wires. Isn't this the correct way this is wired in when in actual use? No clunk, no joy.

News flash...I took the diode off at the control terminal end and when the contactor was energized in this configuration it worked properly. Bad diode? It WAS hooked up properly with the red band on the diode nearest the battery connection.
 
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If you have a digital multimeter you can check the diode. Most have a diode check position. Forward should be about 0.7V. If it doesn't have a diode check position use the ohms range. Forward low resistance, reversed high resistance.
 
8 Builder said:
I have an ES 24115 master contactor. I wanted to hear the contacts close when power was applied. I used a small 12 volt lead acid battery for the test. I hooked the positive lead of the battery to the contact labeled BAT. I then touched the negative lead of the battery to the small control terminal on the front of the master Contactor. The diode is in place and properly oriented. Connecting the negative lead to the control terminal resulted in what seemed like a direct short circuit. Lots of Sparks and heat from the wires. Isn't this the correct way this is wired in when in actual use? No clunk, no joy.

News flash...I took the diode off at the control terminal end and when the contactor was energized in this configuration it worked properly. Bad diode? It WAS hooked up properly with the red band on the diode nearest the battery connection.
Click to expand...

Is the red band a heat shrink on top of the diode? If so, it may not be oriented on the diode correctly by whomever fab'd it. If it is covered in heat shrink, I'd carve that off and see if the line end of the diode matches the heat shrink.
 
Contactor

Thanks guys. I will try these suggestions asap. When it comes to the electrical and electronics end of things; that sure is where the Education part is constantly there for me!
 
Diode test

OK guys, after following your suggestions on testing the diode I have found the following. The diode has the same resistance in either direction. On my very expensive harbor freight multi meter it tests 001 on the 200 scale. Using the diode testing feature, (Which I have never used before), the test shows the same number in each direction. Looks like I have a bad diode.
Since I felt that I would be throwing the diode the way, I cut open the yellow shrink wrap jacket and found that the red stripe on the jacket was on the same end as the stripe on the diode, so it looks like it was assembled correctly.
I don't want to repeat the mistakes I might have made when testing the contactor and causing harm to the diode. Is there any way of applying power to the diode that would kill it?
Thanks for all of the help. Rich.
 
Yeah so it sounds like your diode is dead. Order another and check it first before install. No big deal.

As noted, if the diode was installed at some point where it was forward biased and it didn't have any current limiting (resistor in series) then that may have cooked the diode. Diodes that work or measure the same in both directions are not diodes any more.:D
 
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