A/C and fan speeds

[thom4782]

I've read a number of posts about Boxster fan speeds.

With the A/C off, it's clear the fans are off when the coolant temp is below a specific temperature (say T low) and on high speed above a different temperature (say T high). In between T low and T high, the fans run at low speed.

Here's my question. When the A/C is turned on, do the fan operate at low speed immediately even if the engine has not warmed up to T low? my fans operate at high speed when the refrigerant pressure goes above a certain pressure.

I'm asking because either the fans aren't turning on a low speed when I turn on the A/C or they are on but I can hear them above the engine noise. I don't have a tool to test the fan operations directly.

Thanks

[Meir]

hello thom.
the fans are controlled by 4 different relays, located above the fuse box on the driver side kick panel.
you can remove the relays and "jumper" legs 30&87, to activate each fan in its relevant speed.

let me know if you need more details, i will try to post some pics.

you should be able to activate each fan separately, both in high or low speed.
if one of the functions doesn't work, it usually has to do with defected fan resistor.
with that said, when the fans are on low speed, it is very hard to hear them.

[thom4782]

Thanks Meir:

I tested the relays by putting my finger on each relay and pushing the snowflake button to activate the A/C. When I do this, the relays click, which I could hear and feel. I still can not hear either fan on low speed.

So my next move is to jump the pins. Here's my follow up question. When I pull the each relay, how do I know which pin is 30 and which is 87?

[tony_fury]

Originally Posted by thom4782

Thanks Meir:

I tested the relays by putting my finger on each relay and pushing the snowflake button to activate the A/C. When I do this, the relays click, which I could hear and feel. I still can not hear either fan on low speed.

So my next move is to jump the pins. Here's my follow up question. When I pull the each relay, how do I know which pin is 30 and which is 87?

thom4782:
Most relay have them labeled on the bottom by the pins.
Example

[Meir]

Following Tony's excellent pic,And just to clear.
leg 30 is the center vertical, and 87 is top horizontal.
(purple and red in Tony's pic).

[thom4782]

Thanks everyone for the advice. It was very helpful. Unfortunately, it looks like bad new for me. When I jump the fans to test low speed, neither one comes on. When I jump the fans to test high speed, both work. It looks like I'll need two ballast resistors. I'll have the independent shop test in the morning using its computer just to make sure. Again, thanks

[teleski]

Can you clarify; turning the AC on switches the relays but the fans do not run, i.e. if you walk to the front of the car they are not running?

I ask because I have always assumed that the resistors fail by presenting an open circuit and you can verify their integrity by measuring their resistance < 1ohm between pins 30 of the low and high speed relay sockets. I have yet to let my car run long enough to have the high speed fans kick on. I should probably do the jumper trick to at least hear what they sound like.

[thom4782]

I'll be glad to clarify.

I've preformed several tests. Last night, I turned on the A/C with the engine cold. I could not hear either fan operating at low speed. I waited until the refrigerant pressure triggered high speed fan operation, both fans operated. So I know at this point, both fans work and the fuses are OK.

This morning with the engine cold, I pulled out both low speed relays and jumped them to see if the fans cam on at low speed. They did not. I repeated the test by turning the ignition on. No operation. I started the car with the AC off. Still no low speed operation. Finally, I turned on the A/C. Still no low speed fan operation. When I removed the high speed relays and jumped them, the fans operated at high speed

My understanding is that with then engine cold and the A/C on, jumping the low speed relays will start the fans. In my case, this didn't happen.

If I had a multimeter, I would try measuring the resistance between the 30 pins on the high and low speed relays. But alas, I don't.

BTW: My understanding is that both fans run a low speed when the A/C is on. If I'm wrong, I'd love to hear about it bcause it could be that the fans only operate a low speed when the coolant gets hot enough. If that's the case, then my test wouldn't not have worked because the engine wasn't up to operating tempereature for the thermostat to turn the fans on.

[thom4782]

Does anyone know if it is possible to test the resistance of the ballast resistors using a multimeter in the relay panel. If so, which pins would I use - 30 and 87 in the stage 1 relay sockets?

I'm looking for a way to confirm the resistors are bad before I start opening up the front of the car to replace them.

Thanks

[teleski]

Down in this thread you can find the instructions. Basically you want to measure between pin 87 of the low speed relay socket and pin 87 of the corresponding high speed relay. The ballast resistor is connected across these pins.

The claim is the resistor should be 0.55 ohm. I have a standard dmm which cannot measure this accurately, my leads have nearly half-ohm by themselves. I think you simply want to make sure that you measure 1 ohm or less meaning the resistors are intact. They should only fail by presenting an open circuit, not a short, afaik.

Radiator fan not turning on when AC is off - 986 Series (Boxster, Boxster S) - RennTech.org Forums

[thom4782]

Thanks everyone for the advice especially as it related to jumping the stage 1 relay to see if I could make the fans run at low speed and the pins identifiaction needed to measure the resistance of the ballast resistors.

The car failed both tests. So it's time to unbutton the front and replace the two resistors. And, while I'm doing that, I get to clean the debris between the condenser and the radiator.

[Meir]

Originally Posted by thom4782

Thanks everyone for the advice especially as it related to jumping the stage 1 relay to see if I could make the fans run at low speed and the pins identifiaction needed to measure the resistance of the ballast resistors.

The car failed both tests. So it's time to unbutton the front and replace the two resistors. And, while I'm doing that, I get to clean the debris between the condenser and the radiator.

You do not need to remove the bumper to get to the resistors, but it's a good idea to do so, and clean the radiators. Did that last weekend. Very easy.

[thom4782]

Can anyone suggest a good DIY reference (hopefully with some pictures) for changing the ballast resistors? I'm looking for one that gets at the resistors by removing the fender liner. Thanks