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It's officially the beginning of SoCal's 6 weeks of less than ideal weather. I'm now going on my second season of no heat in my 95 S420. I was trying to figure the problem out last year, but then it warmed up again and I forgot all about it.
Items Replaced: 1. Duo Valve (used but apparently tested for operation) 2. Interior Temperature Sensor in the overhead console 3. Coolant Flush 4. Firewall Hoses that lead to the heater core (unrelated?)
I went through the procedure of pulling the DTCs from the climate control cluster using the instructions on k6jsrf.com
DTCs: 1. 75 Heater supply unit circulation pump (A31m1), open or short circuit 2. 83 Heater supply unit left duovalve (A31y1), open or short circuit **) 3. 87 Heater supply unit right duovalve (A31y2), open or short circuit **)
After clearing the DTC's and driving with the heat set to high for about 10 minutes, only code 75 returned.
Problem I Caused: The 3 pin connector going to the base of the module next to the solenoids crumbled when I removed it while replacing the duo valve last year. I then forgot to look at which order the wiring goes in, so I may have it hooked up wrong. I have tried to move the order around, but no dice. If someone could take a photo of their connector order that would be great. Also, if you have any ideas on where I can buy a new connector?
My first thought is that perhaps the replacement valve is bunk seeing as it's not brand new. Before I jump on procuring another one, I want to gauge your feedback on whether you think it may be something else.
12-14-2021, 05:19 PM
