Best high speed : 1 relay after the switch Reduce overall current flowing in the old circuit : 1 relay before the switch Best of both worlds : 3 relays after the switch Normally you put the relay after the switch in order to get rid of the resistance of the switch (and flaky connectors...). So you would get more voltage if you put the relay(s) after the switch. That's three relays if you want to secure the 3 speeds, but there is not much to be gained in "relaying" the lower speeds. If you look at the spal catalogue p.72 they specify this model incorporates a 3/4 speed resistor (presumably bobbin of nichrome wire) which purpose is to raise the resistance for the lower speeds. My guess, is that the resistance gained through the relay will be marginal compared to the built-in resistor. For sure if you put the relay before the switch you loose a bit of high speed (as some voltage is lost in the switch), but at low speed the current would not pass through the old fuse/relay box, which is the bottleneck of these cars. Regardless on your final layout (before/after switch, single/triple relays) The issue from then on is where to obtain the 12v for the relay(s): maybe you can tap voltage directly from the ammeter as this is as close as it can be from the battery and alternator. You would have to add a dedicated fuse as you are bypassing the fusebox. Maybe a 15A fuse with automatic rearm properly located behind the instrument cluster?
You could salvage the pwm controller from a 12v screw driver, then three resistors (/potentiometer) on the rotary switch so as replicate the trigger of the drill and "drive" the controller. Another solution is that these SPAL can be delivered with 4 speeds resistors, so you can select 3 nice speeds and discard the one you do not like.
Good day Raemin, You could do this, but I prefer I am a bit of stickler for things to be done more formally and precisely. Consequently I will design my own circuit and printed circuit board for this module. Although my approach may appear to take more effort, in the end the resulting solution: a. will be tailored to the issue at hand b. be fully compatible with the motors used (so the design will work, as opposed to might work) c. have a minimum number of components d. be smaller and so easier to install into the dash area e. be easier to install, as the wiring will be specific to our cars. Because of the above the time/effort will actually be less than trying to kludge an existing off the shelf solution that may or may not be designed appropriately for our application (e.g. input transient voltage protection). Lastly, the final design will be professionally done which is in keeping with our cars. Cheers, Sam
The Air conditioning was running very nicely today after it was gased up and I am very happy with the upgrade. Although the compressor didn't turn on as I didn't realise the brown wire needed to be connected up to the 5th terminal on the after market blower switch. This gives power to the air conditioning switch but only after the blower fan is turned on I noticed when I was in some stop/start traffic that the fan on high speed (3) speeds up and slows down slightly with the revs of the engine. So a relay on the high speed output connected from the amp cable as suggested will be on the list to do. I then drove my 2018 Volvo straight away after and thought how similar the air flow and the sound from the fan was to my Ferrari now. Although the temperature won't be as cold
The best thing I've done to my car is to smear (sparingly) silver conductive grease on as many electrical connections as I can get to. This reduces the contact resistance & allows everything to work like it did when it was new. It was amazing how much brighter the head lights were & all fans/blowers & windows sped up. Just be very careful not to cause any unwanted electrical tracks. Cheers, Al https://www.ebay.com.au/itm/CircuitWorks-Silver-Conductive-Grease/163299082186?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
