# Fisher isolation module failure



## tempo12 (Nov 24, 2018)

Hi, everyone -

I've read quite a bit on this site, but this is my first time posting. I'm hoping someone can shed some light on a problem I'm having with a Fisher plow. Here are a few pieces of identifying information:

- Fisher straight-blade plow circa 2008 (I'm not 100% sure; I got it used)
- Minute mount 2, three wires connecting plow to truck
- Three-port isolation module (part number 29070)
- Fisher joystick controller (part number 8292)

The plow worked fine last year. When I went to use it this year, the controller wouldn't power up - the light was off. So I started troubleshooting. Here are some points I've verified.

- There's no power reaching the controller. Wire #1 in the vehicle-side controller harness tests at 0 V.

- Wire #1 in the vehicle-side controller harness is intact and has electrical connectivity from the harness to pin C, port B of the isolation module.

- Power is reaching the isolation module as expected. There is normal power (13-14 V when the truck is running) at pins C and F, port C and pin F, port B of the isolation module.

- The isolation module is properly grounded on pin C, port A (tested with a volt meter connected to battery positive terminal and grounded through this pin).

- The plow headlights work when connected - high and low beams. The plow parking lights also work. The plow right turn signal works but the left turn signal seems not to.

- All plow-to-truck connections have been double checked. The connectors are free of debris and coated with dielectric grease.

Thinking I had a bad isolation module, I ordered a new one. I tried it today, and the plow worked for about 10 seconds before dying with the same presentation as before (and as outlined above). So I'm thinking maybe I burnt out the new module? But I'm really at a loss to explain the causality... I'd be extremely grateful for any pointers or ideas!

Many thanks.


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## dieselss (Jan 3, 2008)

https://www.plowsite.com/threads/diagnosing-no-power-to-control.175150/


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## cwren2472 (Aug 15, 2014)

Edit: darn it!


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## dieselss (Jan 3, 2008)

cwren2472 said:


> Edit: darn it!


 hehehehehehehhehe

Should have let you post your own sticky for the first one...my bad


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## cwren2472 (Aug 15, 2014)

dieselss said:


> hehehehehehehhehe


It's ok. I actually screwed up the cut and paste anyway


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## tempo12 (Nov 24, 2018)

Thanks very much for the tip on that document! I'll follow it through tomorrow and let you know how it goes.


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## cwren2472 (Aug 15, 2014)

tempo12 said:


> Thanks very much for the tip on that document! I'll follow it through tomorrow and let you know how it goes.


Did you ever get this solved?


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## dieselss (Jan 3, 2008)

cwren2472 said:


> Did you ever get this solved?


Just wanna see if your right up saved one from plow malfunction are we?


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## cwren2472 (Aug 15, 2014)

dieselss said:


> Just wanna see if your right up saved one from plow malfunction are we?


Actually, my tutorials insist that the modules rarely fail and it sounds like his module failed. I wanted to see how wrong I was.


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## snowymassbowtie (Sep 22, 2013)

Check the red wire that comes out of the harness that goes to the controller. That red wire should be in the cab close to the 6 wire plug that the controller plugs in, follow that wire to where it goes (it usually connects to a fuse in the fuse box). That red wire needs to be connected to a 12 volt source. It could be a blown fuse where it connects,or the wire could just be disconnected . (Has anyone done any work under the dash ?) You will need to find a 12 volt source,(keyed power is preferred). Your turn signal problems are another issue. It could be one of 3 fuses that are near one the connectors that go into the module. I think there`s three of them, one for each turn signal and one for the headlights ?. Try that and post back.


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## ZamboniHDB (May 8, 2004)

ISO module controls the lighting and no plow operating functions

Did you check the ground wire on the vehicle side of the power harness which ultimately powers the plow motor?


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