Electrical question: any problems adding 12v sources together?

[harpon]

Is 12 volts added to 12 volts still just 12 volts?

Problem- adding a manual "on" switch or an adjustable cooling fan system to the existing one.

Can I have one 12 volt source feeding the fan and the other still possibly coming on?

The need is my 96 Aspire - the radiator fan is controlled through the PCM computer and only has a temp gauge sensor and not a coolant switch-

I don't believe I have the option of getting a cooler switch- i.e. 185 instead of 207 degrees

yet I can get an aftermarket variable temp controller with a thermo sensor that attaches to the radiator, or I could possibly just add a manual switch to turn the fan on earlier.

I don't want to scuttle the OE system which appears to be functioning- I just want the fan to come on at a lower temp. If I add power to the line otherwise, will it damage anything if the OE system then kicks in and throws 12 volts that way as well?


Current bike project- vintage Peugeot mixte frame to mount electric battery on.
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[r34king]

You could wire in a separate circuit and leave the stock wiring alone. But why do you want to change it. Is the car overheating?

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[harpon]

Yes a bit at this point, but other than that I'd just like a larger margin than a fan set to come on at 207, in Florida in the summer. I saw coolant fan switches for other cars that came in variable default temps like thermostats and thought this might be worthwhile if not too much hassle and expense.

I also noticed these on the bay:

https://www.ebay.com/itm/28mm-Water-Temp-Temperature-Joint-Pipe-Sensor-Gauge-Radiator-Hose-Adapter-/272580327993?_trksid=p5731.m3795

a piece of conduit that a generic temp switch threads into, which might be a boon if the other system has problems- and it might also add a little more coolant to the overall quantity, especially if you used longer hose lengths.

[ryanprins13]

I have a manual switch while keeping stock sensor. The switch is ground, not positive. It take a little more thinking to do. Negative is fan off, no negative is fan on

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[harpon]

So it's like the kill switch on my motorbikes. I can't imagine how that works as the circuit gets no power otherwise. Do you have it wired through a relay?
have one of these on the way, though the switch isn't gonna go in my block.

https://www.ebay.com/itm/Electric-Engine-Fan-175-To-185-Degree-Thermostat-Relay-Wiring-Switch-Accessories/181908266542?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

I was out earlier and tested the A/C fan on the other side of the radiator- it came on and even seems to reverse polarity, but I'm not sure if the circuit is turning it on yet. I was going to test it more warm when I got back from the store just now, but got a big cloudburst two blocks from home

I recall the negative switch on the Festy from a few years ago, and I still have to deal with this issue on my '91 which is still parked with 75K on the meter- but I'm wondering if the 96 Aspire works the same, having no separate thermo switch, only the sensor and being controlled through the computer?

Here's some Aspire stuff at Rock Auto:

https://www.rockauto.com/en/moreinfo.php?pk=3843714&cc=1105254&jsn=494

https://www.rockauto.com/en/moreinfo.php?pk=4791498&cc=1105254&jsn=496

https://www.rockauto.com/en/moreinfo.php?pk=3843708&cc=1105254&jsn=739&jsn=739

[harpon]

I'll probably wire the Festy with a negative switch to the tenp switch like ryanprince, but the Aspire only has the temp sensor sending unit- that also sends the reading to the temp gauge. The first unit above is how I may go- attach the sensor to the radiator- the square box is not calibrated, but I can set it by the reading on my thermostat radiator cap, and run the wire to the positive of the fan- it should then in theory send current to the fan leads at a lower temp of my choosing, independent of the threaded sensor and the PCM or ECU computer..

[ryanprins13]

The loss of negative switches the oem relay on somehow. Its on the low current side what i wired in

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[harpon]

Finally ordered one of these-

https://www.ebay.com/itm/Speedmaster-PCE184-1005-Adjustable-Electric-Thermo-Fan-Switch-Kit-12V-/311834715977?_trksid=p2349526.m4383.l4275.c10#viTabs_0

Not sure if I'll put it on the radiator fan or the A/C condenser fan- The radiator relay is functioning normally, but the condenser fan appears to come on only very late- and not sure when it should otherwise.

I've had the old drill out and creating air flow in some other places- that helps too- the Aspire hasn't got a huge grill. Removed a lower panel down below the belts- the water pump is leaking at the bearings- so that comes off when it's changed. The more straight coolant I keep adding the better the condition- I may be ready for another beach run soon, but gotta get this fixed soon.

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