The OVP takes a few seconds to change. It caused erratic behavior on my car, started by killing A/C in city traffic. Then one day driving home the ABS light came on, and I think the tach may have zero'd out (in addition to no A/C). I stopped by the mechanic who pulled the OVP, said he couldn't believe it was in there that long ("antique" was his words
) and he put in another one and no problems since!