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I have a Autopilot PCB which runs a 12v dc hydraulic pump which has been running fine until now. When the pump is not attached the output from the PCB is 12v. When i connect the pump the output drops to 4v and the pump doesn't run. Ive tested the pump and it is working fine.

http://tinypic.com/r/1zciiw3/8

Ive tested the large capacitor and it seems fine. If someone could point me in the right direction as to where I should be looking I'd really appreciate it. Thanks

Only managed to find this diagram. I will keep looking.

http://i60.tinypic.com/ra7p77.jpg

Pump specs

enter image description here

The power supply is a large battery bank which is fed by a 75hp diesel engine.

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    \$\begingroup\$ If you would supply us with some more info (meaning specifications) concerning the power supply and the pump then maybe we can make a useful comment. With this limited info it's anyone's guess. \$\endgroup\$ – Bimpelrekkie Sep 22 '15 at 8:00
  • \$\begingroup\$ If you send a crappy picture of a skin sore to your doctor do you believe a correct diagnosis would happen? \$\endgroup\$ – Andy aka Sep 22 '15 at 8:05
  • \$\begingroup\$ As others have said, more info is needed. Do you have a schematic of the Autopilot PCB? A wild guess with the current info is it may be a faulty NTC (used for in rush current limiting) \$\endgroup\$ – Oli Glaser Sep 22 '15 at 8:40
  • \$\begingroup\$ Apologies. Im trying to find the info now. \$\endgroup\$ – eeejjaaa Sep 22 '15 at 8:50
  • \$\begingroup\$ Fuse, relay, MOSFET (in that order). If the fuse was bypassed at any point or the board fiddled with, maybe blown off trace(s). \$\endgroup\$ – Spehro Pefhany Sep 22 '15 at 11:26
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it seems that your pump need more current. give it from SMPS or transformer (15 -20 A)

if the current supplied is not enough for the pump it will drop the voltage

check your pump current rating and give required current,

pump draws more current when load is applied

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