I finally thought I had all my electrical woes sorted.... Even have an interior light working(Thanks Datto7).

CA18DET grafted into a 1200 ute wiring harness......

BUT - When I took it for a drive last night with the lights on, I noticed the indicator was waaaay slow.
And when the thermo-fan kicked in, the indicators stopped working altogether : - (

So what's the solution?
I'm thinking it may be the switch in the flasher unit (it's a 2 pin cheapie) drawing a lot of current & when the lights & thermo draw, there's not enough to "flick the switch".

When I bought the flasher unit, the guy asked if I wanted a low impedance unit. It threw me at the time because it had 4 terminals & I only needed 2.
Is this what I want?
Are the other terminals to run (accessories)power to it from somewhere else?

I also noticed that the interior light / dash lights dim slightly when the thermo-fan kicks in.
Does this mean I've got a poor grounding somewhere, or is it just the old 1200 wiring struggling to cope with the CA's current draw?

Thanks in advance.

Coops