Can't seem to correct this issue. In the process of replacing all ground straps on motor/frame and freshening grounding screws in dash/radiator support. Re-splicing connections. Can't find a rubbed wire. Any insight is appreciated.
'67 bird (convertible) rebuilt by past owner, 3,000 miles ago. Electric fan located in front of Be-Cool radiator. Toggle switch on dash for fan. Fan works perfect. Summit Racing 3 gauge cluster ... voltage, temperature, oil pressure. Works great.
With engine running, either driving or at idle at a light, gauge cluster works fine, all #s appropriate, temperature reads 190-210. The moment I turn on the fan, gauge needles jump, temp immediately reads 220-230, and voltage changes too. This is an immediate and sudden jump in the gauges with the toggle switch on/off. Then, the needles slowly come down over minutes .... but not back to baseline, with fan on. Oil pressure gauge seems least affected. Turn the toggle off, temp drops on gauge 15-20 degrees instantly.
Thoughts on troubleshooting ? Gauge cluster grounded to metal dash, electric fan grounded to radiator brace. Grew up in my dad's 4 bay 24 hr Shell service station, but electric gremlins are my weakness for sure. My experience tells me bad ground ... but I can't find it for the life of me. Any grey haired wisdom would be appreciated ! Thank you
Electrical issues can make a grown man cry. How is the fan wired? Most guys use a relay to operate a fan like that because the load is so great. Since you are doing wiring, check it out, and maybe re-wire it with a 40 or 60 amp relay so the load is not on the car itself. Remember these cars are over 50 years old and the wiring was not anywhere near what we have today.
You are welcome,and good luck. Also be sure to use a heavy gauge wire, like 10 gauge, or heavier. I have leaned towards using marine grade tin-coated wire for my car projects. The tin protects the copper just in case any water gets under the insulation. Solder all connections, then Liquid Lectric Tape, shrink wrap, more LLT, then finish off with some common electric tape. I rarely have electrical issues after that.
Problem solved ! Though I am not sure which move corrected the gauge jumping issue.
Grounding strap from body to frame on passenger side was missing - replaced it. Grounding strap from block to firewall was at some point removed and replaced with simple wire that was of too small a gauge - replaced it with the correct grounding strap. Battery terminals were worn, with negative side ever so slightly deformed that tightening fully was impossible. Didn't appreciate this until I applied some pressure to it. Replaced both terminals.
Now turn on the fan, and voltage gauge ticks down 1-2 volts (just at switch throw) and comes immediately back to around 14 volts. Temp and oil pressure never move.
Thank you for all the advice. I did pick up a relay and will keep it on hand. That was a great thought. It will be put to use.
