Radiator fans testing and engine temperature gauge
 

2003, base, MT.

I noticed that, at least on the driver side, the fan does not activate on low speed.

Do they have separate relays? Low and High speed? And then separate for Left and Right? 4 relays total?? Any way to test them without Durametric?

Furthermore, if low speed is dead, is it the power supply or the fan itself?

Now, the engine temp.
I was told, 2 years ago, that the water pump was replaced. Sounds about right as I had to burp the system a couple of times. Not much, but noticeable. Now the coolant is steady.

It takes a while for the engine to reach 180 F. I get it, large engine (volume wise), plenty of coolant. Although still too long for my liking....
But then, when driving normally, it stays at 180 or so. On colder days slightly below 180 F mark, on warmer a tad above.

If I push it a couple of times and I reach say 200 region (halfway between the 180 mark and the next one), it will stay there. I do not see much of "down" movement, back to 180 or so, even after a longer steady drive.

What is the normal temp?
Can it fluctuate, in a sense visibly on the gauge, when driving?


My thinking - could the coolant flow be restricted? Could the thermostat be faulty - a tad open on cold - hence long warmup, and not opening wide enough on hot - hence keeping the higher temp longer?

The radiators are clean as I cleaned them last year. Added a mesh to avoid leaves accumulation for future. Mesh opening is about 12 mm square, so not so restrictive.

thanks

On the early Boxster's, the radiator fan speed was controlled by resistors in the circuits, which were mounted on the radiators themselves. As these were prone to fail over time, Porsche later switched to pulse width modulated fan motors, which eliminated the resistors, but when the PWM fails, you need to get an entire fan assembly.

Yours should be the resistor type.

OK, I get it. The resistor would smoothly controlled the speed? Or it would be low and high?


As for testing - without durametric how one would activate speeds.


According to the parts catalogue all Boxsters (986) were equipped with same radiator fan (resistor based). It lists just one part number.

The resistor gives you low speed, no resistor gives you high speed only.

I have never tried testing the fans without Durametric, PST II, or PIWIS; all of which test them with simple commands. But I would imagine that it could be done using a tool like the Power Probe, but you would need to pull off the front fascia to do it, which is why we prefer going the software route.

OK, I get it now. It is like a blower fan resistor but one speed only.

It seems it is easier to get a whole used assembly than the resistor itself.


As for the engine temp - is this what I observe normal?

You need to understand something about the dash temp display in these cars: It is little more than an idiot light that moves. The display itself is nonlinear and well known to be grossly inaccurate.

And as for the fan resistor, people source way cheaper aftermarket version that work perfectly and are often found on Amazon. Do a search on the subject.

I think it’s the opposite. Easier to replace the resistor.

I did a search and aftermarket resistor runs 150 or more.


I did not say easier to replace - easier to get the whole assembly, i.e. cheaper.

Used assembly is way cheaper than the resistor itself.

https://www.ebay.com/itm/185682621714?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=BzI4Ds5DQdO&sssrc=2047675&ssuid=DjOmHBhRQu i&widget_ver=artemis&media=COPY

And post for myself or others to know how to test radiators without PIWIS, Durametric or other expensive tools.

Turns out each fan and each speed has its own relay - yup, a total of 4 relays (53 model).
All of them are next to the fuse box in the foot well.

So if one of the speeds does not work - check the relay.
A 12 V battery charger will work - connect 85 and 86. Then test for resistance across 30 and 87.

Now, with all relays removed, test for power in pin 30.
Use a 12 or 14 AWG wire, strip 20 mm (about 1") of insulation. Using a hammer, smash the copper wire a bit to make it flat blade.
Now you can insert it to the socket.
Connect 30 to 87 (watch the relay orientation).
First insert to 87 and then to 30 (this way you do not have 12 V power in exposed wire).

Each speed will activate.
I do not recall the order, but I believe it was High Left, Low Left, High Right, Low Right - starting from the left to the end of the tray. Relays are 19, 20, 21, 22.

In my case - all relays work OK, low speed is gone on Right, while Left side is grossly imbalanced. Appears to be aftermarket fan which I read are known to be imbalanced.

It may help to remove the 4 screws around the fuse panel to drop the foot well side kick panel.

Ah. Gotcha. Assuming that the used resistor isn’t also bad. I’ve only had one die in nearly 200k miles, so the odds ARE in your favor.

Here's some old discussion about replacing the resistor with an aftermarket one. I have done it on two cars in the past and have not had one of the replacements fail yet after 3+ years. Buy a pair and replace both.

https://986forum.com/forums/diy-project-guides/70000-low-speed-fan-resistor-alternative.html
https://986forum.com/forums/performance-technical-chat/54024-radiator-cooling-fan-resistor-values.html

the ebay or amazon resistors for the fans work great and they are only like 10 or 15 bucks, that will probably fix the lack of slow speed on the fan, as for the temp you are seeing they are perfect on or around 180 and 200 when you push seems very normal, if is taking too long to warm up is not restricted it could mean is to un-restricted in other words your thermostat could be staying partially open when cold