In working out the details for my relay based controller, I realized that I had overlooked the potential of using the Spal Fan PWM controller with the power hungry Taurus fan. I’m assuming that Spal used some reasonably clean form of either Pulse Width or Pulse Frequency Modulation and if so, the 30 amp limitation for that controller can be worked around. The controller (as is, without any modification) should be able to act as the smart front end to a high current switching module. In this environment, the Spal controller would be hooked up just as their instructions call for, except that the connections for the fan would actually be attached to the switching module. This “module” is not much more than a solid state relay & has the capability of taking a lower current pulse train as an input (this part is similar in function to the activation coil of a mechanical relay) & essentially duplicating the timing characteristics of this pulse train with a high current output (this functionally replicates the high current side of the mechanical relay). Essentially, a transistor designed to switch high current, along with a handful of other simple components would let people who already own a Spal controller to extend the use of it to more powerful cooling fans.

 

something like this, Spal---> Ford starter solenoid? (cheap and handles tons of current.) ---> Mark8 on high

 

Unfortunately it's not quite that simple. A mechanical device doesn't have the on/off response needed to be able to handle the square wave that would come from the controller. You need the solid state switch to do the job, but parts-wise, the cost wouldn't be much different from getting a solenoid. I'm looking at some high current switch kits now & if I find something suitable, I'll post a link.

 

I'm assuming that the major problem with the Spal controller was it's poor current handling capability - at least that's what a few on-line complaints have led me to believe. If this is the case, this switch should solve that problem since the controller would be able to operate with very low amps and leave the high current pulse train creation to the switch. If there is a different problem that I haven't heard of, then this mod may not help.

I've found a high current solid state switch kit that looks good and it also appears that I can get my hands on a Spal PWM controller, so I'm going to order that kit (with some minor modifications) and will build & test the rig I described & see how it works. Assuming things work good as I think they should, those that have this controller will be able to upgrade it's capability for less than $20.

I'll post updates as they happen.

 

Well I thought I'd make a brief update to this thread even though I haven't accomplished much. I got a Spal PWM fan controller and found it was quite easy to open the case but when I popped it open, I was really surprised by the complexity their designer put into there. I was expecting a much simpler layout and had thought I could just change a few components on the high amp side and convert the 30 amp capacity to something higher while leaving the smart/semi-programmable end intact. Their board has a lot of surface mount components installed making it really difficult to "reverse engineer" the design and without a good idea of how the circuit is put together I didn't want to go hacking away, possibly destroying it, so I decided to put the case back together and wait for some information on the high current solid state switch I found on-line.

 

The high current solid state switch parts are ordered and should be here next week some time, depending on how well USPS and Canada Post interact, then I'll assemble the whole setup and see how it works - it should work, it's sort of like adding a solenoid to a mechanical relay control unit that can't deal with the current needed.

 

Why so complicated? All you need is an temp switch to kick a solonoid to power the fan.

Thats what I did with the Taurus fan in my Jeep. You can get ones that are adjustable as well. I used one from flexalite.

Also note the Taurus fan needs more than 30amps. A 30amp relay wont stand up to it. I had to switch to a solenoid.

Or are you trying to use the high and low setting? I just used the high on mine and abandoned the low.

 

Well the answer to your question isn't completely simple either. The "why" response to adding a solid state switch to the Spal controller is that the controller is Pulse Width Modulated and can't handle a load above 30 amps and you can't add a mechanical switch like relay or solenoid to a pulse width modulated controller - the mechanical switches can't respond fast enough and you could end up with a single speed fan, a no speed fan, and burned mechanical switch contacts. Adding this switch should give the owners of this controller a wider variety of application. The "why" to my involvement is that I was looking for a pulse modulated controller that would work with fans like the taurus. The "why" to pulse modulation, especially on a high current draw fan, is that you end up with:

• A variable speed van vs. a single or two speed fan giving you better and more stable temperature control for your engine,
• very limited "in rush" current,
• less overall power used,
• less "fly back" current than using mechanical relays and solenoids so you need fewer diodes for electronics protection.
• easier to interface to OEM temperature sensors. With a mechanical relay system, you end up needing 1 thermal switch per speed.

You can use a single heavy duty relay for single, high speed, a single 40/30 amp relay for single, low speed, or almost any automotive relay along with a small solenoid to drive the motor in either low or high speed. I wouldn't use just a switch directly to either a solenoid or motor - both will cause contact burning in the switch (your starter solenoid is kicked off with a relay, instead of directly from the starter switch). To use both speeds on the taurus fan requires more parts and logical layout & the difficulty factor depends on how many bells & whistles you want to include in the overall controller. I have another thread started on putting together a mechanical controller for the taurus fan & will post a couple of schematics in the next few days - this will give people a bit more of a choice of how to change from mechanical fans to e-fans should they want to.

 

Gottcha! You're going for fancy.

The solenoid I'm using is a bit more HD than a regular starter relay(and continuous duty). The 30amp Bosch relay I started out with lasted maybe 30mins so it got tossed pretty quick.

Since the Jeep sees mostly offroad duty simplicity and durability were key. The solenoid controlled by a thermastic probe so far has worked well. I also put in an override switch for manually controlling it. The solenoid also has diode in for kick back protection but as the system stands alone from the rest of the Jeep electrical system it shouldn't really need it.

Is the Spal system similar to the controls that were being made up for the Lincolin Mark IV(?) fans? I read up a bit on that when I did the Taurus fan mod but was more than I needed.

 

The Lincoln and Taurus fans are quite similar and both are quite thirsty when it comes to amps if you turn on the "electric tap" full, but if you use a train of pulses to "bump" the motor up to speed and then adjust the bumps to keep the motor running at any particular speed. This way, you can see what the coolant temperature is (by reading the voltage level coming from the sensor), and increase or decrease the fan motor speed to keep your engine close to a selected temperature. This is how controllers like the Spal PWM are designed to work, but there are very few of these on the market that can actually handle the large cfm fans available from your local junkyard - there's one made by DCC (hard to get, you essentially need to join a fan club to get on a list to buy one), and Painless (this one is about the best I've seen so far, it'll handle up to around 70 amps - I haven't tried it, but the reviews & specs all read good). All the others appear to have taken some serious shortcuts and won't last much longer than your 30 amp relay did when connected to the Taurus style fan. I don't know how Ford controlled these fans, but my guess would be that the ECU would read the coolant temperature and then, based on that temp, would trigger some relays to either turn the fan to LO, HI, or OFF. If they didn't use relays, they wouldn't have needed 2 speeds - the pulse train works on the fan set to it's highest speed potential.