This one has been a real head scratcher in the shop.
The F&R Contactors will not engage on their own.
If we give them a little nudge through the access hole, the snap right on.
This issue has continued despite replacing the entire Contactor assemblies F&R and accelerator.
The EV100 checks out as does the diodes and the osc card.
Voltages are correct throughout and the capacitor checks out good as well using the old Clark "handyman" component tester.
I realize this is an antiquated system but if anyone has some helpful thoughts, we would be grateful!
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Thank you very much edward_t!
Great idea to basically bench test and work backwards from there.
Shorts to frame are one of our first standard tests when something is acting weird.
Thanks for the reminder though.
No park brake switch on this one, we have the company mandated auto engaging park brake that is working properly. Will run through it again just to be sure though.
We service around 400 company owned units out of our shop and we see our share of unusual issues but this one has been a pain for a few days now.
even though you have correct _voltage_ to the contactor coils, the current can be weak, if you have bad switches in the circuit, that are breaking down under a load.
I would recommend taking a set of jumper wires to the contactor coils (remove the wires from the coil to isolate it from the truck's circuits) to "eyeball" the operation of the contactor, and see if it is mechanical binding, or a "weak switch*" before it in the circuit. if it pulls in correctly when jumper-ed, then it is not binding, but is likely to be a switch that has a buildup of corrosion on the contacts of the switch. (my first switch that I would test would be the park brake switch if it has one, then the steering switches, but) any switch in the circuit could be the cause.
Since you say; "have a service manual to know where and how much voltage should be seen" I trust you fully read and understood the part that discusses "before troubleshooting" that is in the manual [before the troubleshooting section], that says to carefully check for "shorts to frame" on all power cables, and too fix any 'short to frame" of less than 100 K ohms, and you have (of course since you have the manual) checked and have clean connections when the battery is disconnected and out of the truck.
Yes, 36 feed to the coil and 13 across when actuating.
We do have a service manual to know where and how much voltage should be seen.
We only have another day or so to troubleshoot and then it will be the old school method of replace parts until it works.
Thanks again!
I think (a lot of times) we get told a "voltage" that is being read across a load, rather than 'with respect to battery neg and no load'.
12 volts across a coil may not be wrong or bad, just more or less worthless information, since the voltage seen is the voltage drop of that particular load's circuit, not the actual output/input voltage of the control circuit. we would HAVE to know where the probe leads are connected and what state the system is in to have any sort of clue. there are plenty of ev100 controllers that use a "pull-in" and then a (less current) "hold-in" voltage (it does not take as much current to hold in the contactor, as it does to pull in the contactor).
I wonder if, when the OP says he replaced the entire contactor, if they actually got the correct coils, and if they disassembled the new contactor as part of putting it in the new truck, as this problem is far more often the hold-down screw of the contactor moving tips, or the pin hole or pin on the bottom of the armature.
Hate to say it but the control voltage is not correct.
GE does not make a 12v system in the EV100 controllers.
Your control voltage should be battery volts which should be either 24 or 36v, which ever battery and controller it has in it.
If you are getting only 13v at the coil supply wire you have a problem and need to backprobe the system till you find where the voltage loss is coming from.
bbforks, I understand what you mean now.
The gap at rest.
The hold down is bottomed out but we will measure the gap and check against spec.
Thanks!
bbforks, was not aware of a a rest setting.
How is that adjusted?
Oem.
Voltages are in spec. according to service manual.
They try to pull but as you said, it acts like not enough voltage.
We replaced the entire Contactor set because we suspected bad coils but the issue continues.
Showing 13v across each coil.
Will just keep plugging away at it.
oem contactors or aftermarket?
the only reason they would not want to pull in is either binding or weak voltage.
there is nothing to adjust on these, everything is fixed
check for voltage drops on the circuit.
Sounds like the magnetic field to pull the contactor in is weak or the setting for the contactor when at rest is too wide. What battery voltage do you have under load?
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