Low Speed Fan Resistor Alternative - 986 Forum - The Community for Porsche Boxster & Cayman Owners

kk2002s · 11-12-2017, 03:43 PM

So right side radiator fan wasn't running the other day as the left side kicked on. Didn't work turning AC on, so I jumped the low speed relay (#21 for right side low - Bentley's has a typo for this) and it still did not operate. I jumped the high speed (#22 for right side high) and the fan worked so it must be the low speed Resistor.
$120 to replace just the resistor and no aftermarket - Are You Kidding me.
$150 to replace the fan with resistor, now that actually seems reasonable.
I'm so cheap so!!!
There are articles on buying an air cooled resistor (.5 Ohm, 100 watt) - $9.95
So I bought (2) for when the left side goes out or I screw up
I was going to have to splice the (3) wires (All Green, Green White strip, All White) If I bought the Porsche resistor so this work was the same
Mounting was the question. There is a metal tab at the back of the chamber where the fan was. I had to simply drill a hole through the plastic, it was at the perfect spot to mount one corner.
I used #8 1-1/4 stainless steel bolts, nylon locking nuts (2/bolt) and plastic wire hangers.

Wiring - All Green wire goes to ones side
- Green/White strip wire and All White wire both connect to the other side
I did not soldier. I used crimp fittings and heat shrink tubing. I may pay for that with time.

I mounted and used a backer for the other hole. I had the inner fender off so I could get to this area easily.

And the final product from the front

JayG · 11-12-2017, 06:35 PM

Nice writeup!

Boxstard · 11-17-2017, 07:49 PM

Did the same fix, very cost effective and so far dependable through the summer after 5,000 miles. If I recall, I used 50w registers slightly below 0.5ohm, and the original clamp could wrap it around just like factory install, after cutting off the mount ears.

Also added a toggle switch to manually turn on/ off the fan, so I got full control to keep the engine cool consistently in heavy traffic during summer, plus easy to diagnosis for bad fan/ register with a flip of the switch.

Gelbster · 11-18-2017, 10:52 AM

If you are concerned about summer heat in slow /no-go traffic. suggest the simple mod of relocating the Temp sensor for the engine compartment purge fan.If you reposition it closer to the cylinder head , it will turn on the exhaust fan sooner/longer.

Quote:

Originally Posted by Boxstard

Also added a toggle switch to manually turn on/ off the fan, so I got full control to keep the engine cool consistently in heavy traffic during summer, plus easy to diagnosis for bad fan/ register with a flip of the switch.

Stiglitz · 06-11-2018, 09:57 AM

I'm about to install a replacement resistor for rad fan.
Is 100w 1 ohm resistor ok?

Currently not running,at least one lead is corroded off the original.

Can't justify $150 for a $5 resistor

Thx in advance
2002 base

Oggie · 06-12-2018, 01:29 AM

The original resistor is about 0.5 ohm. If you have a couple of 1 ohm resistors, put them in parallel and you will be fine.

I replaced mine with a single 0.5 ohm (0.5R) 100W resistor about 6 months ago and it has been working fine ever since.

Stiglitz · 06-12-2018, 03:29 AM

I ordered two, so I'll parallel them. Hope to have them tomorrow. Makes me nervous not having them working, especially with weather in the 90's! (Central Florida).

Thx Again!

kk2002s · 06-12-2018, 06:33 AM

So the product I used was that Arcol HS 100 R5 J as pictured. it is .5 Ohm therefore I only used 1
The fan works as expected for low speed
I did buy 2 so I was ready for the other fan's low speed to die at some point.

Stiglitz · 06-12-2018, 03:28 PM

Installed in parallel, pretty easy.
Did not even have to pull the wheel.

I'll post some pics tomorrow

Working as expected

Stiglitz · 07-24-2018, 06:32 AM

78F350 · 09-08-2019, 04:28 PM

One of my '99s had been running a little hot for a while and I thought it was just from debris in the radiators. Over the course of a year, I cleaned the radiators and replaced the water pump (It was due anyway) It still was running on the 0 in 180 where my other cars would be on the 8. Then, on a long drive it got worse and the AC was blowing warm. BOTH radiator fans had quit working and I had probably been driving for a long time with only one.

I still had a pair of these resistors (if parts are cheap, I buy extras.) from when I did it a few years ago on another car. Once I recognized the problem it was a quick and easy fix.