Aprilaire 4238 Circuit Board<div style="text-align: left;"><strong>[Product Information]</strong><ul><li id="replacementPartsFitmentBullet" class="aok-hidden" data-doesntfitmessage="We're not sure this item fits your " data-fitsmessage="This fits your "><span class="a-list-item"><span id="replacementPartsFitmentBulletInner"><a href="#" class="a-link-normal hsx-rpp-fitment-focus">Enter your model number</a>to make sure this fits.</span></span></li><li><span class="a-list-item"> Aprilaire #4238 circuit board for 4238 700， 760， 760a， 768.  includes wiring harness.  this part does not work with the 700a/700M models (see relay part # 4740) </span></li><li><span class="a-list-item"> Aprilaire 4238 control board for the 4238 700， 768， 760. Circuit board length measures 4"， width is 2" and 11/2 inch high. This controller mounts on the motor board bridge (rp-4243) </span></li><li><span class="a-list-item"> The Aprilaire 4238 700a， 700M and 700 manufactured in 2008 and later are Series two and designed primarily for an automatic humidistat. To turn-on these units require a humidistat that sends 24V to the humidifier </span></li></ul></div><img src="http://ecx.images-amazon.com/images/I/41z%2Bws1I8uL.jpg" noproxy>