I have this glow plug :
https://www.ebay.com/itm/NEW-Mercedes-W140-W126-350SD-300SD-350SDL-S350-Diesel-Glow-Plug-Relay/151364568887?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
during prestart up I have ABS light come up and goes away soon as car is running. Cruise control is working. AC is another issue. It's working , well compressor and producing super cold air, but working only with short plug, as I bought this way. I got new relay as you told me , but it didn't fix a problem, it will not turn compressor on, but it may be too cold now. I will try to nail air conditioner close to summer time.
Would be air conditioner not working because of this OV relay?