Probably a varistor rather than a simple resistor. I suspect they've just simplified the symbol.
Varistors are commonly used in electronics as voltage limiters/arresters. In this case it will be to limit the back-EMF generated by the relay coil, to prevent interference and potential damage to the relay drivers.
https://en.wikipedia.org/wiki/Varistor
A diode can be used instead (across the relay coil), but has the disadvantage of slowing the relay movement, which can result in contact arcing/burning.
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Mark
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2002 FE S8 Ebony Black Pearl
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