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Central Heating & Storage Heaters Forum
Honeywell V4073A mid position valve not moving: motor or PCB?
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<blockquote data-quote="jt12345" data-source="post: 455991" data-attributes="member: 29695"><p>I *do* like this forum system, but it does take a little bit of "getting-used-to" at first! <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p></p><p></p><p></p><p>Yes, I'm aware of that. But since moving or touching anything has "temporarily fixed" (irony alert!) the problem twice already, I'm inclined to just spot-probe potentials/voltages if that provides me with the same info (and it should do!) Another issue with removing the power and using the meter on the ohms range is that there is of course the parallel circuit through the diode, switch 2 and the 13k resistor which might modify the resistance measured, so I feel certain of how to interpret the reading.</p><p></p><p></p><p></p><p></p><p>I thought I had. I posted on the 20th Nov: "Yes, it does". But I'm not sure that my response was indicative of anything since, as I added at the end of that same post "It's a classic intermittent problem - every time I strip it down, it starts working perfectly!"</p><p></p><p>I had a good look at that circuit diagram over the weekend and all of a sudden I realised that if both of the inputs to switch 1 are live, (and *if* the switch is working correctly!) then the switch's output should be live too (an equivalent statement to "its resistance should be zero"). So I now realise that my very first post contained the answer to my question:</p><p></p><p></p><p></p><p></p><p>If I'm only getting ~63V on the motor feed (the same as the switch output), micro-switch 1 *must* be (intermittently) "fubar'ed". I've just sprayed both micro-switches with contact-cleaner and it's now working. Time will tell...</p><p></p><p>Thank you, ProDave and Rob_the_rich, for your help - I think I've got this circuit understood now. With best wishes, jt.</p></blockquote><p></p>
[QUOTE="jt12345, post: 455991, member: 29695"] I *do* like this forum system, but it does take a little bit of "getting-used-to" at first! :-) Yes, I'm aware of that. But since moving or touching anything has "temporarily fixed" (irony alert!) the problem twice already, I'm inclined to just spot-probe potentials/voltages if that provides me with the same info (and it should do!) Another issue with removing the power and using the meter on the ohms range is that there is of course the parallel circuit through the diode, switch 2 and the 13k resistor which might modify the resistance measured, so I feel certain of how to interpret the reading. I thought I had. I posted on the 20th Nov: "Yes, it does". But I'm not sure that my response was indicative of anything since, as I added at the end of that same post "It's a classic intermittent problem - every time I strip it down, it starts working perfectly!" I had a good look at that circuit diagram over the weekend and all of a sudden I realised that if both of the inputs to switch 1 are live, (and *if* the switch is working correctly!) then the switch's output should be live too (an equivalent statement to "its resistance should be zero"). So I now realise that my very first post contained the answer to my question: If I'm only getting ~63V on the motor feed (the same as the switch output), micro-switch 1 *must* be (intermittently) "fubar'ed". I've just sprayed both micro-switches with contact-cleaner and it's now working. Time will tell... Thank you, ProDave and Rob_the_rich, for your help - I think I've got this circuit understood now. With best wishes, jt. [/QUOTE]
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Honeywell V4073A mid position valve not moving: motor or PCB?
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