[oaejames]

I’m trying to track down an electrical problem in a ‘89 5.0. When the head lights or park lights are turned on while the windshield wipers are on the wipers slow to a crawl or stop completely and all of the dash gauges go “off scale”. This happens at all wiper speeds. The muti-function switch was suspected and replaced, but the problem was not resolved, has anyone out there ran into this problem?

[reddogsmustangs]

Try another head light switch, then look for high resistance in wire harness.