Questions about new fan + SDS compatability

[MikeFleming]

Mike, what size wire, relay and fuze would you recomend with that spal fan?

Me Mike??

Depends on total length of cabling required. It's nominally a 20Amp circuit, so 12 gauge. If more than 8 feet of total cable length (power + return/ground) then use 10 gauge. Larger is always better. use 30 or 40A rated relays in sockets for each replacement, if needed. Solder connections to relay socket for best electrical conductivity.

And if you're gonna get technical use red jacketed wire for power, black for ground/return. Hide them in that black cable wrap stuff so it looks pretty.

[SchoolBoy]

Ha ha, yes Mike I ment you. Now would I be correct in say'n I need to 2 40amp relays wired in parallel? Also Do I need a fuse between the power block and the relays?

[MikeFleming]

Why two relays??

Yes, there should be a fuse in the circuit somewhere - either from the starter solenoid battery terminal to the r4lay power circuit or between the relay and the load (fan).

[SchoolBoy]

The two relays was just something I had read. The Idea being that the 2 relays will share the load when you turn the fan on keeping it from over heating the relay.

As for the fuse, to me it would make sence to put it between the relay and the starter solenoid that way it protects the relay and the fan. Unless the spike would come from the fan killing the relay?

[MikeFleming]

One relay is sufficient. Assuming the fan will draw a start-up peak in the 18Amp range, and fall back to ~12 when at full speed, I would use (1) 30 or 40A fuse (in an insulated fuse holder), one 30A relay (in a socket) and 10 or 12 gauge wiring.

In series as follows (text electrical diagram!):
Solenoid battery (+) terminal ->
fuse - 30A ->
30A relay power side contact ->
Other side of relay contact ->
fan power (+) connection

Fan (-) connection ->
Secure, clean, direct chassis ground (fair) - OR - direct connection or battery negative (-) terminal, cable or ground block (best)

Then the coil side of the relay is pretty simple. One side goes to the same ground wire as the fan power leads. The other coil wire goes to whatever you're using to trigger the fan - such as the previous power out form the [working] SVO fan controller to the stock fan. Coil wiring can be relatively small - 18 gauge is fine.

[DaveS]

The two relays was just something I had read. The Idea being that the 2 relays will share the load when you turn the fan on keeping it from over heating the relay.

Relay contacts have maximum current ratings; I suspect the duel relay setup was due to the contacts not being rated at or above the protective device rating (fuse). By choosing the correct relay (if possible), you'll not have to parallel relays.

The downside of putting two relays in parallel is that you cannot guarantee the amount of current that will pass through each of the relay contacts. As the contacts wear and become pitted, resistance increases and the flowing current will decrease through that set of contacts and increase through the other set. No guarantee that you'll split the current evenly.

Choose a relay with contacts rated for the flowing current (or as close to it as possible) and be done with it. If you have to parallel contacts, you can get a relay that has a pair of contacts (like a DPST switch); this will obtain the parallel contact arrangement you noted earlier.

With all that being said, the fewer times the relay has to close and open, the less wear on the contacts. Program your on-off points with as large an amount of hysteresis (A property of a system such that an output value is not a strict function of the corresponding input, but also incorporates some lag, delay, or history dependence, and in particular when the response for a decrease in the input variable is different from the response for an increase. For example, a home thermostat with a nominal setpoint of 75° might switch the controlled heat source on when the temperature drops below 74°, and off when it rises above 76°.) that is realistic.

[SchoolBoy]

I only need a 4 pin relay, but a 5 pin will work just don't use the 5 pin correct?

[Raven855]

I only need a 4 pin relay, but a 5 pin will work just don't use the 5 pin correct?

I added this relay last weekend. It is a 4 pin 30 amp. I used 10 gage wire on the supply and ground because that is what I had.
image.jpg

[SchoolBoy]

Well we got this all installed and running, but it keeps poping the 30amp fuse, any ideas.

[MikeFleming]

The fuse blows in microseconds or minutes?

First thought is the wiring is not right. But it's really hard to tell from here.

[SchoolBoy]

Minutes/days. I drove the car 2 Saturdays ago 80miles to the show and it was fine except the headlights dimmed to about 1/2 strength. So since then we have been working on replacing the alternator, a bunch of questionable wiring at the voltage regulator, back of the amp, both battery cables, and one spout wire. We hooked everything up today and started our test to see if the charging system would keep up. It does ok until the fan kicks on then it drops to 12.3 ish. But during this I would turn the spal on with the defrost switch. On two occasions the 30amp fuse has blown during these tests both done within 2 hrs of each other. Now the fan does not run and stop while in defrost mode. It runs, I switch it off, then go to switch it back on and we get nothing no spin at all.

Pics to come in a bit. We used 12 ga wiring.

[SchoolBoy]

Also on the fan itself is a spal sticker with type va18-ap71/LL-59A 12v I'm wondering if this motor isn't a 60amp motor?

[Meotchh]

Also on the fan itself is a spal sticker with type va18-ap71/LL-59A 12v I'm wondering if this motor isn't a 60amp motor?

No it is not a 60A motor. For the motor to draw 60A, it would have to have a resistance of approximately .216 ohms. Now if you check the motor, & observe resistance of less than 0.416 ohms, then I would say you have a bad fan motor. If you measure a resistance of approximately 0.619 ohms, you have one of the following problems:
- a wiring problem
- a relay problem
- an odd intermittent problem with the fan.

It's not impossible that the fan would be the problem in that scenario, but it is unlikely.

[SchoolBoy]

Meotchh, the fan did in fact measure a resistance of .200 ohms. I will be calling Spal on Tuesday to see what they say....

[SchoolBoy]

So I called Spal and they told me to try a 40amp relay and fuse first. He said the motor I have is power hungery on start up. So I ran down to napa and snagged one. So far it worked last night but I didn't run it to long.

[MikeFleming]

IMHO, get a different, lower-power fan and motor. That much current draw is never a good idea.

If it were my car, I'd be happier to see something with less than 20A start-up and less than 15A run current.

[Meotchh]

So I called Spal and they told me to try a 40amp relay and fuse first. He said the motor I have is power hungery on start up. So I ran down to napa and snagged one. So far it worked last night but I didn't run it to long.

If the fan motor has a resistance of .200 ohms, it is pulling far greater than 40A. If you told the Spal representative the motor was measuring .200 ohms & that person told you a 40A relay would work, I suggest you talk to someone else there that understands BASIC DC electronics. I gave you the formula so you can calculate the current draw given that you know the resistance of the load & the supplied voltage. Having that information you should already know a 40A relay & fuse will NOT work.

Further more, I would suggest you ask Spal to supply you with the electrical specs for that fan motor. Resistance & tolerance would be all you need to understand how much current it will draw.

[MikeFleming]

If the fan motor has a resistance of .200 ohms, it is pulling far greater than 40A.

at 0.20 Ohms, it would pull 70 Amps at 14 VDC. THAT would be totally unacceptable for automotive use. imho.

[rodster]

at 0.20 Ohms, it would pull 70 Amps at 14 VDC. THAT would be totally unacceptable for automotive use. imho.

Do I smell smoke?

[MikeFleming]

BTW - a 70AMP circuit should have 4ga wires. Might get away with 6ga for a short distance though.