One of my rad fans has stopped working...
 

Is that likely the motor or resistor pack? How do I tell?

Thanks!

Assuming the fan runs in high speed mode but not low, most likely its the resistor.

If you have a Durametric cable, you can activate the fans in low and high speed. If the one that is NOT working in low speed, runs at high speed, then its the resistor of the relay.

If you don't have a Durametric, then you can try a few other things.

You can test the relay by switching the low speed ones one for the other. If the fans operate at before with the relays switched, then it's not the relay.

You can test the ballast resistor. Here's a link that show how. http://986forum.com/forums/general-discussions/38026-c-fan-speeds.html.

If the fan doesn't run at any speed and you've switched the relays and the working fan still works, then the motor is the more likely culprit.

Good luck

The fan does not appear to operate at all currently.

I think the other one only operates in high speed mode...

The only thing I'm 100% certain of is that one fan runs in high speed mode while the other either fails to operate or is running in low speed mode. This is assuming it's not obvious when a fan operates in low speed mode. If it is obvious when the fan is running in low speed mode, then as above - one fan high speed only, the other fan dead.

Most likely the resistor. They fail all of the time.

The radiator fans in the Boxster run at two speeds. The low speed runs when the car engine temp is higher than 206°F or the A/C is on. The high speed runs when the coolant temperature is higher than 215°F or the A/C freon pressure is higher than 16 bar. High speed fan operation simply goes straight to the fan. The low speed is created by sending power through a ballast resistor which reduces the power to the fan and creates the low speed operation. The resistor is prone to failure.

Here is the test sequence that I followed:
(1) Fuses
(2) Relays
(3) Fan motors

First, check the radiator fan fuses, Row C, #8 and #10, 40A.

Next, test the relays - Start a cold engine, trans in neutral with parking brake on. Get down on your knees and put your left hand up on the low speed relay (either #19 (left) or #21 (right)), then reach up and turn on the A/C with your right hand. If the relay is good, you'll feel a "click" in the relay and the fan will turn on in low speed. Turn a/c off and the relay will click again. You can also do this test using a Durametric to turn the fans on to low (my version of Durametric does not have high/low, just on/off and on is low speed). If a relay fails to click, replace it.

http://i1114.photobucket.com/albums/...psaaa101ec.jpg

Next, test the fan motors by jumping the relay to force the fan to operate at high speed. Remove both the low-speed (#19 for left) and high-speed (#20 for left) relays for the fan that isn't working (or #21 and #22 for right). Cut and strip a piece of wire about 1.5" long. Insert one bare end in the output socket (pin 87, center bottom horizontal slot) for the low speed relay and the other end in the output socket for the high speed relay.

http://i1114.photobucket.com/albums/...ps37620c9a.jpg

With the jumper in place, put the relays back in and test. Start the car cold, turn on the A/C, and verify that the fan is now operating (it will be at high speed because of the jumper). If the fan is running at high speed with the jumper, then the ballast resistor (which controls low speed operation) has failed. If not, then the fan motor itself has failed (because it won't operate at either low or high speed).

A replacement resistor is about $100-$125.

With your clarification try these things...

1) Set the internal car temperature to as low as it will go. Start the car and turn on the AC. Get out of the car and move to the front so you can hear the fans. Both should operate in low speed. If neither fan is running in low speed, then I would guess both low speed ballast resistors are broken. This was the case for my car.

2) If you find in step 1 that one fan runs in low speed and the other doesn't, turn the car off and switch the low speed fan relays. Then repeat step 1. If the fan that didn't run in step 1 starts running and the other one stops running, then you have a bad relay. If the fan that did not run in step 1 still doesn't run, then that fan's ballast resistor or the fan motor itself is broken. Steps 3 and 4 will help identify if its the motor.

3) Steps 1 and 2 focused on low speed operation. Step 3 and 4 will test high speed. Begin by switching the high speed fan relays. If the fan that does not work in high speed starts working after the switch and the one that worked originally stops working, then the relay is the problem and you'll need a new high speed relay. And you will have ruled out a broken fan motor.

4) If the fan still doesn't work in high speed, then you'll need to jump the high speed relays as described in the URL I posted earlier (thstone's post shpws a picture). After jumping the relays, if the fan still doesn't work, you probably have a bad motor. To finally sort this, you might have to test voltage at the fan motor.

Hope this is more helpful.

Thanks guys. How much do the relays typically run. If they're cheap, first step might just be to replace those...

First step should be just to test them via the touch and click method thstone mentioned. Really, it's pretty easy to do. Did mine this way trying to figure out why my drivers side fan would not work in low speed.

If you plan to keep the car though, get a Durametric or used PST2/PWIS so you can perform better diagnostics and turn on functions like this. It'll be worth the money you'll save going to the dealer the first time you use it.

The relays are cheap ($10) but its almost never the relays. That would be too easy and too inexpensive. :D

Thanks, I'll probably bag a relay or two just to be on the safe side!

OK, today the dead fan was working. Weird.

Any thoughts on what might cause an intermittent fault. Probably rule out blown fan motor for starters...

Do both fans run at low speed when you run the engine with the AC on so its blowing cold air? If both work at low speed, then the resistors are OK. If one doesn't run at low speed, the ballast resistor probably needs replacing. When the AC is off, the fans run at low or high speed depending on coolant temperature.

If low speed operation is intterment with the AC on, one guess is that the ballast resistor is beginning to fail (crack) and it hasn't reached the point where it fails completely. Once a ballast resistor fails completely, the fan will not run at low speed under any conditions

Thanks, I don't think low speed works on either fan and never has during my three years ownership. I'm in the UK, so can go quite a while without activating the fans due to generally cold ambient temps. Sometimes months.

So the situation as far as I know is that neither fan runs at low speed and one fan is intermittent at high speed. It definitely didn't trigger a couple of weeks ago when the other fan was running at high speed. But today both fans definitely were running at high speed as normal. Would this be the resistor pack?

Also, do the replacement motors come with resistor packs?

I'm assuming you've played around with switching the relays and perhaps tried jumping the sockets as shown in the diagram in one of the posts. If so and the fans operate as you describe, then I'd would replace the ballast resistors on both sides to get low speed operation. The low speed operation helps the AC condensers work more efficiently.

You can replace the ballast resistors in two ways. One is the simple approach where you remove the fender liner, cut the wires leading to each resistor and splice in the wires from the new resistors. I did this and it took about 45 minutes per side. I used heat shrink over the splices to seal the connections. ILook at this thread for more detail: http://986forum.com/forums/general-discussions/38026-c-fan-speeds.html

The other way is to remove the fender liner and the cover for the fan. Then you replace the resistors. I did not do this because of the extra work so I'm not sure how the resistor wires connect. They may just plug in.

I don't know why one fan would work at high speed and the other one would work intermittently. Perhaps the high speed fan relay is loose or there is a poor connection. No idea really.

PS: I'm not sure, but I don't think the motors include resistor packs.

Yes. The parts geek fan has the resistor and the whole assembly is about $160.the resistor alone is about $110, so it makes sense to buy the fan assembly and replace everything to be on the safe side.

Small update.

The fan is now working consitently all of its own accord. I'm 100% certain it wasn't working that day. I'm 100% certain is has worked every time the fans have spooled up since. That day was the first time since the winter the fans had been triggered, out of interest.

I assume it's a cracking ballast resistor behind this odd behaviour. I'll keep an eye on it for now...

Reviving old thread
 

So how do I differentiate between low and high speed?

I have a 99....both fans operate, fuses are good and relays click. I'm just not confident the low speed is working. Fans come on with the AC, but they are loud. I find it hard to believe it's "low" I'm hearing. Car runs a bit hot...fans kick on and cool her down. I thought it may have been due to the temperature outside but it was cooler today and when I drove it it still get hot and the fans kicked on to cool it down. It usually heats up to just below the 100 hash mark and then the fans kick on. After a ton of reading on this I do know that the gauges are notoriously inaccurate. I just would hate to run the car hot. So is there anyway to if the fans when they're running are either on low or high? It's never overheated, I am between low and high coolant mark on the reservoir and I have the newest .04 blue coolant cap.

Am I worrying about nothing? Install low temp thermostat?