Hvymtlc5

My 78 came with two spal fans that were wired by Bubba. Would like to restore their functionality to the most effective use. Should both these fans be wired to a relay and sending unit to come on when a certain water temperature is obtained (like my C5) or should they come on one at a time (see kits for this)?

To me the install would be simpler if I have them BOTH set to come on at 200 degrees. Does it make a difference?

Bullshark

For my application on the 502 RamJet, I kept them independent, one sensed by water temp, and the 2nd tied to A/C (or staged to a higher temp sensor)
Here are a couple of thoughts that may help you decide:

1) There can be a pretty healthy surge on the alt if you dump both start-up fan loads (25amps each) at the same time. Better have an alt and volt regulator that can handle the instantaneous loads of your TOTAL system in addition to the inductive kick that switching on and off both fans at the same time will induce. Very good grounds are very important.

2) With my Be-Cool aluminium radatior, the BB runs cool as a cucumber with just one fan in most hot summer days, w/o A/C

3) Variable fan speed control sounds attractive, but I don't think it is necessary, at least in my application, especially if you stage the two fans at two temps.

Just a couple of $.02 thoughts

Bullshark

Ganey

Staged.

Hvymtlc5

I don't have A/C and it's not in the picture for a while......so I guess I could build a relay to turn the second fan on maybe 5 seconds after the first so the amp draw isn't so high. Other choice is that since I have a 4 core alum. radiator (never really driven thae car before I took it apart) I may not even need the second fan.....?

gkull

I have one set to come on with the ignition key and the other is a manual toggle switch so I can have it run when I'm out of the car or if i see the temp gauge climbing.

Hvymtlc5

Another good idea with a manual switch! I keep thinking all the complicated ways with relays and sensors. Good old toggle switch and good temp guage could keep it simple.......

gkull

I bought the lighted toggle that handles 50 amps or something. so I can see that it's on. I also have a manual switch for my OD lockup

chris75stingray

thats how i have mine. i only turn the fan on when the temp reads about 190+ . i have an aluminum rad with only an electric fan and i hardly use it.

Hvymtlc5

Since I don't have the A/C installed anymore ... instead of installing another toggle switch I think I will wire the fan to the "hot" compressor wire and then I can turn the fan on by using the A/C switch......

shafrs3

Another option that I've had success with is a soft start module from Summit Racing or Jegs. It starts the fans slowly thereby softening the shock to the charging system and varies the fans speed according to engine temp.

Boofers

I would wire them in series for low speed operation and parallel for high speed operation. Use a relay to switch between the two settings. Put your temp sensor monitoring the radiator temp, not the engine temp.

78pacer

I installed the dual SPAL's in my '78. I used the wiring that came with Dewitt's kit and a 195 deg temp sensor in the intake manifold. It's an easy job if you have the relays, wiring and sensor as a kit. Call Tom Dewitt and save yourself a lot of unnecessary time and headaches.
Mike

0Tom@Dewitt

We have now changed to standardize on the SPWM (controller) for our fan controls. The older relay package and switch is still available but I think Spal will eventually drop it because the controller does so much more. The SPWM controls one fan by itself and for dual fans you need to buy the extra relay harness (SPFRH). You never want to wire the fans together or in series. Each fan should be individually fused and protected so you loose a fuse, not a fan.
The SPWM will ramp the fan speed as needed instead of running full blast. It is also capable of using the stock temp (gauge) sending units so you do not have to install anything into the engine, simply tap off the gauge sender. The controller has a two-prong plug for the sender and a lot of the older ones are single. This can still work by using the green wire only. But just to make sure that you are not going to have trouble, we now include a two prong switch with each controller. When you run two fans (duals) the controller works in conjunction with a relay harness. You then have a primary and secondary system. The controller ramps up the primary fan and if it gets to full speed, then it kicks on the seconday fan and starts ramping the primary again. It has auto AC accuation if you have that feature. Direct link

shafrs3

Mr. Dewitt,
I've looked at the PDF file detailing the specs of the Spal 11" dual fan unit. With respect to the static pressure column that relates to airflow and amperage values, what does this static pressure figure mean? Is it a pressure the fans might encounter behind the blades? If this is true I can’t imagine a situation that would cause this.

0Tom@Dewitt

Puller fans are like vacuum cleaners, sucking air through the radiator core. Spal lists a range of air flow/amperage for different restrictions in front of the fan. The thicker the radiator or density of fin, the higher the restriction. The higher the restriction, the higher the amp draw. Just like when you put your hand over the vacuum hose, you can hear that motor scream. In most cases, you can use the middle of the range to estimate your air flow/amperage unless of course you're doing something really special.

shafrs3

Thank you. That makes perfect sense.

tersian

Tom,

Bought your direct fit with the dual SPALs, it only came with one relay so I wired both through that relay, I blew the fuse the other day and started thinking one relay wasn't such a great idea, so now I see SPAL has this new module out, can you PM me the price on this and maybe an ideal of how to make it work with the sender I have installed instead of having to wire it into the sender going to the gauge. I like having senders at two distinctly different spots on the engine.

78pacer

Tom,

I would be interested in the pricing as well. I think that is a good design.
QLakes@charter.net
Mike

MEGALADON

Wow, I need one of those to.

0Tom@Dewitt

Here it is boys!
controller