Light on speedo even when ignition switch is off--flashing battery on speedo after atv is started

You are not alone.

https://www.google.com/search?q=2018+Polaris+Sportsman+Highlifter+1000%2C+no+start%2C+no+electrics

..

If your HS400ATV is not powering up even with a fully charged battery and you've already replaced the ignition switch, there may indeed be another module or component that could be causing the issue. Here are a few possibilities to consider:
1. Main Fuse: Check the main fuse for the ATV. It is typically located near the battery or within the fuse box. Ensure that the fuse is not blown and is making proper contact. A blown main fuse can prevent power from reaching the ignition switch and other electrical components.
2. Starter Solenoid: The starter solenoid is responsible for engaging the starter motor when you turn the ignition key. If the solenoid is faulty or not functioning correctly, it can prevent the ATV from powering up. Inspect the solenoid for any signs of damage or loose connections. Consider testing the solenoid or replacing it if necessary.
3. Kill Switch/Safety Interlock: Check if there is a kill switch or safety interlock feature on your ATV. These safety mechanisms are designed to prevent the ATV from starting under certain conditions, such as when the brakes are not engaged or if the ATV is not in neutral. Make sure these switches are in the correct position and functioning properly.
4. Wiring and Connectors: Inspect the wiring harness and connectors for any loose, damaged, or corroded connections. Pay close attention to the connections between the battery, ignition switch, and any other modules or components. Clean and tighten any loose connections, and repair or replace any damaged wiring or connectors.
5. Electronic Control Module (ECM): The ECM or other control modules could be a potential source of the issue. These modules control various electrical functions in the ATV. However, diagnosing and testing these modules often requires specialized tools and knowledge. It may be best to consult a professional ATV mechanic or an authorized dealer who can properly diagnose and test the modules if needed.
If you've checked these possibilities and the issue still persists, it is recommended to seek professional assistance. They will have the expertise and equipment necessary to diagnose and resolve electrical issues specific to your HS400ATV.

check the battery volts while running, should be around 14

2004 Sportsman 700 AWD not working..... - Polaris ATV Forum

www.polarisatvforums.com > ... > ATV Repair and Maintenance
Feb 18, 2013 - Go Back · Polaris ATV Forum > Polaris ATV Technical Discussions > ATV ... AWD wont engage. 2. The instrument / speedo works. 3. The AWD switch is ...Polaris ATV Junkie! .... four wheel drive not working polaris sportsman. Won't go into 4 wheel drive
Feb 1, 2013
4 wheel drive not working
Nov 13, 2011
2004 700, 4WD engages by itself
Oct 28, 2011
4wd is stuck on
Dec 3, 2009
More results from www.polarisatvforums.c

check safety switch (emergency shut off)

Sounds like a bad switch

2002 polaris 400 atv wiring Bing images

Take your battery to O'Reilly's or AutoZone and have the CCA (Cold Cranking Amps) checked..(load test).. this WILL tell you if your battery is good or not.
Just because you have 12 VOLTS doesn't mean it's A GOOD BATTERY..You MUST have amperage to start/run your ATV

If the green light isn't on in the dash it won't start even if in neutral. If it is then it's probably the neutral switch

the solenoid for the ignition and starter has failed. Also remember the brake has to be applied to activate the starter system.

My 400 has a brake switch interlock. Don't forget to check that function.