Have been riding weekly for few hours each week in same place. Yesterday had an overheating flashing display and full bars on temp with beeping. Stopped and checked coolant level which was between lines on resivoir. Pulled and swapped fan relay, no change. Then ignition off for a minute then back on. After a few seconds the fan cuts on (engine off) and bars go down and it's OK.
Happened 3 times near the end of our 30 mile ride. Mostly slower trails, no climbing or mud. Just dirt, woods, and grass. Radiator clean. I only have about 270 total miles on the machine. So it's not muddy, beat up, or abused. Always have 2 riders so we generally take it easy. We spend 3+ hours for these 30 miles, stopping to fish or crab.

On third overheat I noticed that while trail cruising (10-20 mph) my thumb stays steady but something changed in how the engine was responding from perfectly smooth to light surging and immediately the temp bars started to rise. Took about 5 minutes until beeping and flashing warning. When it happened the third time I knew it was something related because I noticed it the first 2 times but disregarded it. I would compare it to how a new rider rides and tries to ride very slowly but they aren't used to the thumb throttle so they bump it back and forth so the machine surges up and down in rpms especially with rougher terrain (ruts and bumps) but I am very used to my throttle and wasn't moving it at all when this started.

I've never had it back to the dealer because it's 2 hours away and only problem previously was a starter relay that I replaced myself a while back.

Any ideas? We were done for the day so I don't know if it will keep doing it but it probably will. We have over 100 hours on these same trails at easy speeds with no other issue prior to this.

[2015 Z Force 800 53/Trail EPS]

On the new ones the fan relay is triggered by the ECU which gets it's info from the coolant/water temp sensor...which as I recall has two sections, one for the dash display and one set for the data to the ECU. If the relay and the fan motor are ok, and it appears they are, then there either has to be an issues with that temp sensor...which there have been in the past, or some intermittent connection somewhere for the fan circuit..possibly the fuse box-related....or something with the ECU. Either/or the fact is CFMs can not take being over heated even once...let alone 3 times now. Need to find and fix the problem before the next ride. 

Thanks for the reply. Gotta to let it run to day for about an hour and of course, no signs of any overheating or any odd behaviors. I didn't ride it, just idled and revved some. It stays at 150f and the fan comes on and off everyrdew seconds and I get the normal 4 bars on the coolants. gauge.

There is a plug that was touching the radiators fill neck wrapped in the radiator cap chain so I moved it out of the way. Not sure what it is, maybe a sensor or something.

It didn't seem to be hot when it was beeping Sunday but that doesn't really mean anything. I have attached a few pics. Coolant was green and clean and full. I hate chasing problems like this.

I let it run for another half hour to really get it heat soaked. The fan wasn't running every few seconds anymore and it was starting to climb bars on the gauge so with careful preparation and water hose blasting I removed radiator cap to a geyser of green coolant all over.
Being uninjured, I then decided to check the relays again. 2 of them seem swollen and I'm wondering if the heat soak is causing them to go bad but only when very hot. Picture attached.

Problem is the relays test fine on the test bench but they maybe be cooling down quicker than I can test them.

[2015 Z Force 800 53/Trail EPS]

Why are they getting so hot...if that's what's happening. What is "Heat Soaked" Have you tested the amp draw on the fan motor?

They may be crappy relays. I ordered a pack of new ones so I'll switch them and see what happens. I continued to let it run for a while and it didn't repeat the issue after moving the relays around from other slots. I can test amp draw and see buy I'm hoping this is the issue. I will also look at the temp sensor at the radiator.

"heat soak" is when you've been running a long time, especially at low speeds and the whole engine compartment gets hot because of the heat. Everything is hot. It's normal but weak parts can't take it.

Hello, I'm new here. Just bought a new 2021 zforce 800 trail.took it out for the first time yesterday. While driving up a dirt mountain road , at about8 miles I heard like a compression pop behind the seat didn't see anything but decided to turn back. Got about 1/4 and noticed the temp rising 4 bars. I shut it off  then turned it back on temp sign was flashing and all bars lit up. Waited about 15 min , turned back on still 4 bars. Pushed and coasted couple miles turned back on still hot. Checked fluid level, it was full. opened over flow no movement, then pulled radiator cap. Made a mess. Walked back for truck and trailer drove in a far as I could. Went back to cforce, finally cooled, put some water to fill up. Drove it to the trailer then dropped it off to the shop.  Any ideas what went wrong? I haven't heard anything from the dealer yet. Didn't hear a fan kick in at anytime. Should I be worried about damage to the machine? Thanks

[2015 Z Force 800 53/Trail EPS]

Hello, I'm new here. Just bought a new 2021 zforce 800 trail.took it out for the first time yesterday. While driving up a dirt mountain road , at about8 miles I heard like a compression pop behind the seat didn't see anything but decided to turn back. Got about 1/4 and noticed the temp rising 4 bars. I shut it off  then turned it back on temp sign was flashing and all bars lit up. Waited about 15 min , turned back on still 4 bars. Pushed and coasted couple miles turned back on still hot. Checked fluid level, it was full. opened over flow no movement, then pulled radiator cap. Made a mess. Walked back for truck and trailer drove in a far as I could. Went back to cforce, finally cooled, put some water to fill up. Drove it to the trailer then dropped it off to the shop.  Any ideas what went wrong? I haven't heard anything from the dealer yet. Didn't hear a fan kick in at anytime. Should I be worried about damage to the machine? Thanks

Could be several things but making a sound like that and way-overheating...especially so new.. concerns me. Hope the dealer can fix it. Let us know.

I have the same problem. Its not the reley. It is the automatic fuse for the fan. He is in the black plastic box on your picture. You can order same type of ffuse or you can put ordinary  auto fuse

In this box

I changed with this one but bigger ampers then original

Thanks. After removing and re-plugging the problem has not come back but I will keep that in mind.

I have a 2019 800xc.  This past weekend was the second time the engine got hot.  The fan relay was very hot.  I th8nk it stopped working until it cooled off.  This was after about 40 miles on trails at about 5 or 10 miles per hour.  It was about 55 degrees F. 

Is there a higher quality relay I can get that will hold up a bit better to heat?

[2015 Z Force 800 53/Trail EPS]

I have a 2019 800xc.  This past weekend was the second time the engine got hot.  The fan relay was very hot.  I th8nk it stopped working until it cooled off.  This was after about 40 miles on trails at about 5 or 10 miles per hour.  It was about 55 degrees F. 

Is there a higher quality relay I can get that will hold up a bit better to heat?

Any relay built..anywhere other then China is of vastly better quality..however do know that relays that run hot usually indicates they are pulling at or near their amp load limits for a prolonged period. Most of these relays are rated at 20 amps...China's probably a little less. Yes, replace the relay as it is most likely toast but check the load. It may be that the fan motor itself had a problem and is pulling way more amps then it should. Not enough to blow a fuse..yet but getting close.

The relay's coil can also be a problem and run hot however it will also show to pull more milliamps then it should. With the right tester that too can be checked. As I recall they are usually somewhere between .050 and .035. This was the problem with many older units with fan switches. They would pull closer to one amp which caused the old fan switches to get hot and burn out internally. Those that went through several switches finally replaced the relay and ended the problem. The new ones don't use a fan switch, they use the ECU to ground the relay as needed bu the input from the temp sensor.