The previous owner of my 64 installed SunPro gauges - gas/temp/oil psi/volts. All of these seem to be working fine. However whenever I flip the switch to run my wipers (one speed) the gauge (except the oil which is mechanical) needles kick back to the far left. Once the wipers are off, they're fine again. Any ideas? I'm not that informed about electrical stuff so any advice will be appreciated!