Hi Dennis, I have the Isotherm 3751 ASU SP system and I experienced something similar last Fall. The unit was alternately flashing yellow/red and was not working. I shut turned off the power at the breaker, clean up the defrosted moisture in the bottom, and threw out the mayo, mustard, and ketchup. I turned the unit back on and it started working. I started reading up on Isotherm ASU trouble shooting, but the unit has been working fine since.
Prior this occurrence, I noticed a good amount of frost build up on the cold plate which I attributed to a poor seal on the access lid. I have since improved the lid seals and added a 1” foam mat (cut from an exercise mat) to cover over the whole top. I don’t know if it was the power cycling, some odd frost build up issue with ASU, or something else, but the units has been continuous running fine for over 7 months now (knock on teak). - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ > On Jun 18, 2020, at 12:00 PM, cnc-list-requ...@cnc-list.com wrote: > > Date: Thu, 18 Jun 2020 09:23:23 -0500 > From: "Dennis C." <capt...@gmail.com <mailto:capt...@gmail.com>> > To: CnClist <CnC-List@cnc-list.com <mailto:CnC-List@cnc-list.com>> > Subject: Stus-List Isotherm ASU refrigeration troubleshooting > Message-ID: > <CANir+ysYh5t772=UN8Bqh0-740=ZZh8u02mKP=zcugh2onf...@mail.gmail.com > <mailto:CANir+ysYh5t772=UN8Bqh0-740=ZZh8u02mKP=zcugh2onf...@mail.gmail.com>> > Content-Type: text/plain; charset="utf-8" > > For those of you with a similar system, Touche' has an Isotherm 3701 ASU > refrigeration system. Got on the boat last Friday and it was not running. > The thermostat panel was alternately flashing yellow/red. > The operating manual said this indicates a fault in the electronic module. > > Following Isotherm's and generic Danfoss/SECOP compressor troubleshooting > procedures, I removed the red Isotherm ASU control module from the Danfoss > control module. It was simply plugged in and was easily removed by > pulling. (The ASU module senses voltage on the boat and increases chilling > when it sees increased voltage due to shore power or the engine running.) > > With the breaker off, I jumpered the "T" (thermostat) and "C" (compressor) > connectors on the Danfoss module then flipped the breaker on. There is a > 60 second delay built into the Danfoss control. This is NOT reflected in > troubleshooting tips. After 60 seconds, the compressor kicked on. That > indicated the fault may be in the thermostat circuit. > > I removed the telephone jack style thermostat connector which was plugged > into the ASU module, applied Tefgel, plugged it back in and out a few times > and put the unit back together. Voila! It works now. Just a dirty > connection on the thermostat plug in connector. Love $0 solutions. > > When I installed the unit, I had coated all the connections except the two > telephone jack style connectors with TefGel. Now all connections are > coated. > > -- > Dennis C. > Touche' 35-1 #83 > Mandeville, LA
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