kyreb1862 said:
I drove the car this morning with the headlights, heater fan and wipers on and there was no slowing of the turn signals. It only seems to happen when the cooling fans kick on.
Okay, now, what happens (and I will repeat myself),to headlamp brightness, heater fan speed, etc, when the cooling fan comes on and the T/S are activated.
Does the charge indicator glow?
Do the headlamps get dim?
Does the heater fan slow to less of a breeze than normal?
I see you tried everything else on, but did not see any reports on ammeter.
You may have a higher resistance in the feed to the fan and t/s if they are on the same circuit.
A relay will bypass directly to battery for fan feed.
Now, just for a drill:
Engine off, keys in pocket, bonnet open.......how loose is the fanbelt?
Can you turn the cooling fan by hand without the crank turning?
One of the reason I asked about the ammeter in the first reply was that a bad alternator, poor alternator connections, or loose (slippping) fan belt under high load will also do that, BUT it will also manifest itself in other electrical functions.
The heater fans can be a fairly high draw, or, the fans could be on their way out, like bearings going bad.
Have we spun the cooling fans by hand to see if they are starting to lock up?
Another off-the-wall issue that I have seen before (not often), is rust.
I have seen body/chassis rust issues that adversely affected the ability of the ground path of the power at the load to return to the source.
Fenders (wings) where they bolt down, radiator supports, engine to frame, battery, etc.
Now, theoretically, if the fan ground (common) is connected to the same place electrically as say the front turn signals, and the corroded/rusted grounds will handle the turn signals, but not the fan, and cause the turn sinals to slow when the ground point voltage level increases when the fan is on......
I have no idea the condition of your vehicle/grounds/wiring changes/ etc.
Got into the shop this morning to look up the electrics.
Main power feed off battery terminal of starter solenoid goes to pin 7 of fuse block.
Main power to ignition switch also comes out of 7.
The (usually) green wire direct to the thermostat for cooling fans also is in 7.
BUT:
Fuse in pins 5 and 6 next to 7 and 8, 6 feeds the turn signals (and all sorts of other bits).
IF you or someone (shop or P/O) has connected fan thermostat to the wrong pins (most likely the one next to 7, which is 5), you are no longer loading direct from battery, but now off the feed to accessories.
Something to look at anyway.