Plumber needed for HW mixing valve

4240 Marble Ridge Rd near bass lake road, El Dorado Hills CA

Description

We need a plumber who knows how to fix a hot water mixing valve. The water in the heater is pretty hot (118 degrees - we set it at 120), but when we turn on a shower, it seems that the mixing valve mixes in too much cold water. As soon as the water starts flowing, the dial thermometer drops, even though the HW riser from the HWH stays scalding hot. See the attached photo. We have tried adjusting the valve from stop to stop, but that changes nothing. Would like to find a plumber who can either a) fix the valve (replace the guts?) or b) disconnect the current valve and put in one that works. I believe the piping is 3/4"