Thermofan problem

[Dooley]

I've got a little 10" thermofan that replaced the belt driven fan in my Sierra, I'd originally got that for a front push fan but did an engine change and wanted to keep the Swift pulleys, so put that on the radiator by itself. Little small but one of those things where it works for now so leave it be.

It runs whenever the cars on, the relay is triggered by the ignition so it's on constantly whenever the car is.

Now just today it wasn't turning on with the ignition, I got rid of a waterproof connector that I'd been having problems with and put some bullet crimps on, only to find that it wasn't the connector, a fuse had burnt out.

I replaced the fuse, the fan ran for about a second or two and then the second one popped.

Now I've disconnected my wiring and checked it all, infinity ohms from power wire to chassis, infinity ohms from power wire to negative wire. So it's not a short.

To make sure I put in a 15A fuse, my wiring can easily handle that, not so sure about the lead off the fan so I didn't run it for long and anyway the fan was running fine.

Now I'd checked the current draw of it a few weeks ago, had an inrush current of about 9.6A and the avg current running was 7.5A, so there is no way it should be blowing fuses. However it has stopped working once before due to a fuse melting in the cheap inline holder. I put that down to too much contact resistance in the holder...

I'm thinking for some reason the fans drawing quite a bit more current than it's supposed to.

Anyone got any guesses ?

[chimpboy]

It's difficult to say, but it's hard not to think that the fan might just be on the way out. The fact that it's running all the time would contribute; normally they're only on when you're doing very slow speeds or idling, so running them 100% of the time eats up their lifespan pretty fast.

Given that they don't cost much, I'd suggest obtaining a new fan - perhaps a bigger one, 12 or 14"? - and hooking it in. If it doesn't blow the fuse, you know the fan was the problem. If it does blow the fuse, you'll still have some troubleshooting to do but you probably won't be sorry you got a better fan.

And then either way, I would really recommend looking into a thermoswitch for the fan. I would think there already is one on the swift motor, surely.

[chimpboy]

By the way, I just checked a fan I have here, it was off a 1990ish Barina which I think was a rebadged Swift, and it's about an 11" fan. So I guess a good 12" would probably do.

[murcod]

It does sound like your fan is dying. Does it still spin freely by hand?

I'd suggest the biggest fan you can fit in (10" is way small!) and renewing your wiring to larger cable. (The less voltage drop you have in the cable the faster your fan will run- even 0.2v will make a noticeable speed difference.)

I'd also use a 20amp fuse after renewing everything.

[Dooley]

It's difficult to say, but it's hard not to think that the fan might just be on the way out. The fact that it's running all the time would contribute; normally they're only on when you're doing very slow speeds or idling, so running them 100% of the time eats up their lifespan pretty fast.

Given that they don't cost much, I'd suggest obtaining a new fan - perhaps a bigger one, 12 or 14"? - and hooking it in. If it doesn't blow the fuse, you know the fan was the problem. If it does blow the fuse, you'll still have some troubleshooting to do but you probably won't be sorry you got a better fan.

And then either way, I would really recommend looking into a thermoswitch for the fan. I would think there already is one on the swift motor, surely.

It has a Sierra intake manifold, I'm guessing that's where the Swift one would have gone ?

Far as I can tell the Sierra doesn't have one, what looks like a thermoswitch is I'm guessing the sensor for the temp gauge, it's only got one contact.

What's the best way to add one in, can you figure out what voltage the sensor is at x temperature and have that as the switching point ?

Or is that too unreliable and you really need a dedicated thermoswitch ?

It does sound like your fan is dying. Does it still spin freely by hand?

I'd suggest the biggest fan you can fit in (10" is way small!) and renewing your wiring to larger cable. (The less voltage drop you have in the cable the faster your fan will run- even 0.2v will make a noticeable speed difference.)

I'd also use a 20amp fuse after renewing everything.

It spins freely by hand. Well I'm going to see what will fit, thinking maybe 12 or 13". Yeah I go for at least about 5A overhead in the wiring over what the fuses are rated at. I used 15A wiring for this fan.

edit: Actually how about a t-piece for the thermoswitch ?

[chimpboy]

You can buy adaptors at autobarn etc ... you cut the top radiator hose and put the adaptor there, and it has a threaded hole for a thermo fan switch.

They look like this:



But what I did was drill a hole in the thermostat housing then tap thread into it for a sensor. But you need an M16 tap which is not common.

For an idea of common thread sizes and temps, see: http://www.outerlimits4x4.com/phpBB2/ftopic147839.php

Or get one that's a spare part for a Swift then get the adaptor to suit, then you know it will be at the right operating temperature and play nicely with the thermostat.

[stuee]

You can by an after market thermo fan switch from davies craig. Supercrap and the like sell them. When we did my mates car we used one and it has a probe that sits in the radiator hose. Its a long wire like probe that squeezes out between the hose and the hose connector so you don't have to cut any hoses or add t-pieces and what not. We also didn't have a problem with leaking. Only issue we've had so far was a supercrap relay sticking on otherwise its been very reliable.


Linky to product:
http://www.daviescraig.com.au/main/ther ... p?prodid=1

From memory the kit cost about $60. Could probably buy something a lot cheaper from the wreckers but this was easy and it had an instruction manual

[nicbeer]

that one that chimp has posted up is good.

i run one in my sierra for the mech water temp gauge.