[djustice]

I have had 2 generic 12" 80W "china" fans that has been on the car for the last 4-5 years, they are fed by 2x 20 AMP relays, and each fan has a 15 AMP fuse.

These fans draw about 6-7 amps each , but on a really hot day stuck in traffic the temp wil start to very slowly creep.

I have just gotten 2x spal VA10-AP50/C-61A - 1221 cfm
According to the data sheet they draw maximum 14,5 AMP each.

Now i installed them and ran the car up to temp, while i watched the holley efi handheld to se when the ecu triggerd the realy for each fan: Fan 1 on i hear nothing go to check and it is not spinning, wait for fan 2 .. and not spinning.
I check the fuses and both are blown, so i change to 20 AMP fuses letting the car cool completley down. same story when i bring it up to temp, both fuses blow,
now i shut the car off and reinstall fuses do a hot restart and both fans Work!

Next day after it is completley cooled down same story again both fuses blow on intitial startup, change fuses and both fans work on a hot restart.

The fans probably has a lot of inrush current on intial startup

I find this strange as it is my understanding that as a wire or component gets hotter resistance increases, i find it odd that the fuses blow when cold, and not hot..

Per now i have tested with 25 AMP fuses and it seems to hold for now (2 hours of driving) but i dont want to overburden the realys , so this is not a permanent solution.

[george kujanski]

Electric motors have an inrush current that can be many times greater than the running current. That is most likely what you are seeing. You may need to upgrade the relays also.

George

[johnta1]

I'd try using a (resettable?) circuit breaker instead of fuse.

Like this pic

[ID67goat]

Originally Posted by george kujanski

Electric motors have an inrush current that can be many times greater than the running current. That is most likely what you are seeing. You may need to upgrade the relays also.

George

Agree with this. I think I would size the relays and fuses for 2X the nominal current.

[djustice]

Thank you all for the pointers i'll do some shopping.

[Speargun]

What AWG wire are you feeding the circuit with and how long is the run?
I would feed those fans with at least 12ga wire, direct from the battery, through a quality relay, and make sure that all connections & grounds are good. I was burning up the Bosch 30a relays so I installed a 12v 80amp continuous duty solenoid.

[djustice]

Seems i misunderstood the rating of my relay, it's a dual realy rated at 40 amp, i was under the impression that both relays in the same enclosure where a total of 40 amps.
Turns out it is 2x40 amps so i am good with the 25 amp fuse fuse for each fan.
I am running 2.5 mm2 wire size i think that is 14 AWG. The run out of the relay to the fans is about 2.5 foot, the pigtail comming out of the fans seems to be the same wire size.

[roger1]

The purpose of a fuse is to protect the wire and not the device.
So you pick an amperage based on the gauge and distance of the wire. This is why you always should place the fuse as close to the source as possible. Otherwise it defeats the purpose of having a fuse.

There are charts to help you do that.

Here's one I like:

[djustice]

Thank you for the chart, it seems everything is as it should.
Just a little confusion over the relay amp rating on my part.

[HWYSTR455]

Yeah, the current draw is rated at a constant, and on-spike can be high. If you're turning them on-off-on-off at full, the spike can be harsh. Not just on the relays or wiring to the relays, but everything between ALT-BATT and fans.

I'm willing to guess that C-61A at the end of the part number is that spike.

Just to say, I would suggest running 10g wire, and a good grade wire, not your parts store 'hook up' wire. GXL wire is the minimum I would run.

They make 70a relays that the one power tab is slightly wider, and work in the same relay holders, you just need a larger spade terminal for the holder.

Auto reset or solid state relay are not cheap, and can run upward of $70. You would be better off running a PWM fan controller, that have 'soft start'. It will make the fans last longer too.

.

[HWYSTR455]

Waytek has a selection of solid state relays:

https://www.waytekwire.com/products/...-State-Relays/

Poke around there, you will see the typical bosch type 70a ones, and the terminals too.


.

[djustice]

Originally Posted by HWYSTR455

Yeah, the current draw is rated at a constant, and on-spike can be high. If you're turning them on-off-on-off at full, the spike can be harsh. Not just on the relays or wiring to the relays, but everything between ALT-BATT and fans.

I'm willing to guess that C-61A at the end of the part number is that spike.

Just to say, I would suggest running 10g wire, and a good grade wire, not your parts store 'hook up' wire. GXL wire is the minimum I would run.

They make 70a relays that the one power tab is slightly wider, and work in the same relay holders, you just need a larger spade terminal for the holder.

Auto reset or solid state relay are not cheap, and can run upward of $70. You would be better off running a PWM fan controller, that have 'soft start'. It will make the fans last longer too.

.

You are rigth, i would love to run a pwm controller but i dont know how that will play with the sniper ecu output grounding them.
Rigth now the sniper is controlling the fans and it's just ground on/off, it Migth not matter at all if it turns on a relay that activates a pwm controller?
I am probably overthinking this too much

[HWYSTR455]

You would just run the controller outside/independently of the Sniper, the temp trigger would be from the controller's own sensor. No need to use the Sniper to trigger it.


.

[JSchmitz]

You can also get slow blow fuses that will accommodate a brief spike.

[djustice]

Originally Posted by JSchmitz

You can also get slow blow fuses that will accommodate a brief spike.

That was my initial intent, researching this it seems glass and porcelain is the most common style for slow blow, not so much blade-style. But there seems to be a company named littlefuse or something that makes those,

[JSchmitz]

Originally Posted by djustice

That was my initial intent, researching this it seems glass and porcelain is the most common style for slow blow, not so much blade-style. But there seems to be a company named littlefuse or something that makes those,

Yeah, I'm not sure on the blade style. The old "AGC" glass fuses do:

https://www.napaonline.com/en/p/BK_7821335

[roger1]

I use the time-delay Midi/AMI fuses made by Littelfuse. Waytekwire.com has them and fuse holders for a really good price. Blade type fuses don't work well for higher draw devices like fan motors. For relays that are used in the engine compartment, I use Hella weather-sealed skirted relays. Waytek carries those too.

[Scott65]

I've been successfully using fusible link wire ahead of my 40 amp relays for awhile now. Not sure if it's technically correct but it's been reliable and trouble free for years now. However, I use a power distribution lug right behind the headlights powered by 8 gauge wire to power all the relays up front, headlights, and fans, and at one time an electric water pump. In other words a short run from a rugged power supply.