Honeywell 40003916-003 3-Port V4073A issue?
Over the course of a few weeks the heating and hot water has been a bit of an issue, issue being intermittent hot water and heating, initially thought it was this silly tado thermostat i have + i replaced the router so thought that might have been the issue and then problem went away after a few days. Suddenly yesterday, no hot water and/or heating, the tado thermostat is calling for heat and hw, i can see the lights pop up for both when activated in the app . I took a look at the 3 port valve and can see there is absolutely no resistance on the switch at all, when heat or hw is called, i can hear a whirring noise like the switch is trying to move to the left/right but it struggles to get anywhere... am i right in thinking there should be some resistance when moving to left to right, the switch is comletely free and no resistance whatsoever... tempted to replace just the head as maybe the motor and/or spring is goneski... only replaced this about 5 years ago, thought these things lasted an eternity... maybe they dont make em like they used to... any better ones out there? i currently have Honeywell 40003916-003 3-Port V4073A
Advice from 5 local tradespeople
The issue is likely with the 3-port valve, specifically the actuator head, not the thermostat or router. The lack of resistance when the valve is switched indicates a problem with the motor or spring within the actuator, possibly due to age or wear and tear. Replacing just the actuator head might be a viable solution. While 5 years is a relatively short lifespan for a valve, they can fail prematurely. There are other brands available, but the Honeywell V4073A is a common and generally reliable option.
Yeah first of all I would check the wiring
Making sure when calling for heat
You have 240v on the white wire
If calling for water only should have power to orange wire nothing on grey
If calling for both heating and hot water
Nothing on grey 240v on white If this is all correct
Change the synchron motor inside valve head
Change for an EPH head. They have ones with a Honeywell adapter. better and easy to change once new wiring is installed. 3 port valves go all the time some within the year but most just outside so out of warranty. 5 years is good going.
The 3 port valve needs replacing, if it's Honeywell you can usually just change the head
Sounds like you're on the right track, and you've done a solid bit of troubleshooting already. Based on what you’re describing — intermittent issues leading up to complete failure, the actuator motor making a noise but not actually moving the valve, and the lack of resistance when manually moving the lever — it definitely points to the motor or internal gearing in the actuator head starting to fail, if not completely gone already.
Yes, normally there should be some resistance on the lever when it's working properly — especially when it’s powered off — as it's connected to a spring-return mechanism. If it feels totally loose and moves freely with no spring-back, that’s a classic sign the internal spring or motor mechanism has packed up.
The Honeywell V4073A heads are generally pretty reliable, but like you said — they don’t always last forever, and 5 years isn’t unusual for one to go depending on system use and wear. You can definitely try just swapping the actuator head rather than draining the system to replace the whole valve body, which saves time and mess. Just double-check the spindle on the valve body itself still turns freely — if that’s seized, you’ll need to replace the whole valve.
As for alternatives, Honeywell still makes decent gear, but some engineers rate the Drayton Mid-Position Valve actuator heads (like the MA1) slightly better in terms of durability and motor longevity. That said, compatibility and wiring layout will differ slightly, so stick with Honeywell if you want a like-for-like quick swap.
