Is this a starting or run capacitor
- Thread starter LazyDog
- Start date
![IMG_9268[2237].jpg](/forums/data/attachments/98/98362-91612df7cdee8066ee893f2664a99475.jpg)
Its a starting capacitor, the fans can draw up to 40 amps!! That's a lot more than I would have ever expected.
Volvo and Saab use 2 fan relays for the engine cooling fans, this I believe is the same type of resistor, if it fails and they frequently do there will be no fan operation whatsoever. Are your fans are not working? The fix is not difficult.
this is a Saab unit.
This the one I use and mount it on an aluminum plate further up away from the engine.
ARCOL part # HS100 R22 J
HS100 Series Aluminum Housed Axial Panel Mount Resistor, 220mOhms +/-5% 100W
This is the basic wiring for it.
ARCOL part # HS100 R22 J
HS100 Series Aluminum Housed Axial Panel Mount Resistor, 220mOhms +/-5% 100W
This is the basic wiring for it.
Last edited:
So is that resistor meant to increase the amperage to the fans? Is it true that some cooling fans can use 40 amps?
I literally took electricity 1-3 in collage 10 years ago.. I can't remember anything about current and resistors, its sad really. Use it or lose it..
I literally took electricity 1-3 in collage 10 years ago.. I can't remember anything about current and resistors, its sad really. Use it or lose it..
Think I answered my own question.. The resistor is used to control the speed of the cooling fan. 2 separate circuits, one uses the resistor to keep the fan operating at a lower speed. The based on the engine temp sensors data, a circuit without a resistor is used to power the fan at an increased speed to increase cooling of the engine.
Now, how do both of the fans turn on at speed for the ac condenser cooling?
How does only one fan operate at a lower demand for speed based on temperature?
Does the PCM use the temp sensor input value to select each fan condition? AC operation switch provides a input to the PCM that outputs a speed condition too? Pretty neat little computer circuitry.
Now, how do both of the fans turn on at speed for the ac condenser cooling?
How does only one fan operate at a lower demand for speed based on temperature?
Does the PCM use the temp sensor input value to select each fan condition? AC operation switch provides a input to the PCM that outputs a speed condition too? Pretty neat little computer circuitry.
The above fan was a new replacement for the older style w/ out the resistor.
The cooling fan low speed is control by the PCM using the temperature sensor. The high speed is control by the AC been on.
The high or low inputs are run into a relay that outputs the desire speed.
The cooling fan low speed is control by the PCM using the temperature sensor. The high speed is control by the AC been on.
The high or low inputs are run into a relay that outputs the desire speed.
The Volvo only has 1 large relay.
Like this one? What year and model is this? This is a Volvo high low, I understand it replaces the 2 individual ones on later models and later than this they used an electronic module. How does it switch to high speed without the AC being on?
EGT sensor tells PCM temp, PCM puts out voltage signal to power a relay, that selects 4 different conditions per input voltage?
No, the resistor is needed for both fans to operate, if it dies no fans work. The systems that use the resistor is a bit of a weird setup that uses 2 sensors the resistor and the pcm to control fan speed.
On this one (Saab) it runs on low on one fan the high on the same one then both high, the AC switch enables the high speed relay which automatically triggers the other fan. One sensor is in the radiator and the other in the rear of the head.
Regardless if it is 2 individual relays or a module it performs the same job.
Even if the both relays (or the double relay module) are in perfect working order the resistor is the weak link. In the picture the OP posted you can see the three wires going into the resistor like the diagram I posted 2 wires in one out to the fan motors.
So does the PCM have one wire with differing voltage outputs? Two wires with differing voltages?
On this particular car IIRC 1 wire it goes to the low fan relay. Both relays are intertwined, I will look for the wiring diagram. Other cars that use 2 relays have 2 wires from the PCM that go to terminal 86 on both relays.
Edit: this one is not a variable speed just a simple high/low.
Edit: this one is not a variable speed just a simple high/low.
The Volvo cars that I am aware that have this set up is 93-98 model years and it includes 850, S70, V70 models.
From what I see on my car, the low speed is run by the computer using the temperature sensor as reference. When I turn the AC on it goes into high speed.
Hmmm, I thought the engine computer controls the fan's speed via pulse width modulation (PWM) (https://en.wikipedia.org/wiki/Pulse-width_modulation). Yes, these fans do draw a ton of current. My car's fan fuse is 50amps!
Many newer cars do but most older models probably do not.
If it is a later model it probably is triggered by the ECM but the ECM is still triggering relay(s) either old clickers or an electric module. the ECM cannot carry the amps the fans require.
