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Husqvana CTH 172 Ride on lawnmower

149 Views 2 Replies 2 Participants Last post by  swalshire
Hi all, new to this site but I hope you can shed some light on an electrical issue I have. I have a ride-on mower that I have restored from being in a tired state. When I bought it, the guy before me had sealed shut the bagger sensor & the deck engage sensor. I thought nothing of it at the time but I can see why he did it now.

My issue is, after starting the mower, the moment I go to engage the deck, it cuts out electrically, once the sensor button is left to release. I have looked at the push button sensor in question & it is getting 12 volts across from starter to key as it should from looking at below. But when button is left open by moving handle away the circuit is broken.

I checked the sensor & its working correctly. Normall Closed on when button pushed in, Normally Open when button out. What I see is that I am getting 12v across the Norm Open pins when engine running with button in but once I release it cuts out.

I found out I can overide this by pulling out the 12v wires & then the sensor works correctly & deck will engage with button out. However I believe this is not correct, I have discovered that the seat sensor does not need to be in circuit for mower to start, nor does the bag interlock work.

Apologies for the detail but I am stumped on this. Also I have 3 relays on the mower but only see 1 on the schematic ?
Font Rectangle Schematic Parallel Engineering

Would appreciate any help or if there was a more detailed schematic available.

Thanks, Sean
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are you using the word "sealed" as in relay logic noting that once the circuit is actuated it will maintain itself closed?
I kind of follow some of what you are saying. Could it be the extra relays were an attempt to modify the circuit to defeat or enhance the safety circuit?
Hi Laser3kw, sorry yea, what I mean is that he used a small nail to jam in the button & keep it closed on the bag sensor & clutch (deck engage) sensor. When the ignition is turning, the contacts are closed to allow current flow from 1 to 2. (clutch sensor).

Then when you allow the button to spring out, contacts 1 & 2 open to stop the starter & also closes the contacts allowing current to flow from 3 to 4. But when you do this the engine cuts out. The 12 volts going through 3 & 4 are causing that. If I remove 3 & 4 from the sensor, the engine will stay on with button out on sensor. This is what should happen, sensor is only to allow engine start without the load of the clutch engaged.
Font Line Parallel Rectangle Diagram
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