Rebuilding Rear Duovlave. Will 13% difference in DCR work?

[pcmaher]

I'm in the process of rebuilding my rear duovalve assembly in my 95 S600. The left rear duovalve (A31/1y1) coil winding was open. I took the assembly apart, and measured the diameter of the coil wire at 0.0144 inches. The closest I can translate this to in AWG size is 28 gage HML magnet wire. Total turns was 1, 150. Total DCR of the original coil is 15.4 ohms. After removing the old wire and winding new wire on the bobbin, I get a DCR of 17.7 ohms. This is a 12.99% difference from the original winding. I am assuming that this difference is because the wire size is not 28 gage, but a metric size close to 28 gage. This concerns me. A difference of 10% wouldn't bother me so much. Since this system is logic controlled, I assume that the position of the duovalve plunger can be infinitely adjusted within it's limits. If the coil DCR is off by 13%, I am concerned that the plunger may not be positioned correctly during operation. Does anyone out there have a good understanding of the duovalve operation to tell me if this will cause a noticeable difference in performance?

[Brett San Diego]

This is the valve that opens to allow hot coolant to flow to the heater core, right? It seems that it should just be an on/off thing. Either hot coolant gets delivered to the core or it doesn't. The cabin temp is then modulated by turning the heater blower on and off controlled by temp sensors inside the cabin.

It seems too complex to try to regulate temp by regulating how much coolant flows through the heater core. But, then again, plenty of things may be overengineered in these cars.

Good luck with the fix.

Brett

[myarmar]

It is on/off, but not as simple. It is getting PWM signal from the controller. The flow is regulated by changing duty cycle (on vs. off time). I don't think 13% will make a difference. As long as the valve can open and close with available battery power you should be OK. System will regulate itself.
Reg. Mike

[pcmaher]

Excellent feedback. Duty cycle makes sense. I saw no means of proportioning these valve partially open / closed. They are designed to be either open or closed. I'm documenting this as I go, and am posting the details as I have time on my webpage. Thanks guys.