Couple of radiator fan questions

@Dr.Jeff - thanks for all the info! I suppose the thread is the same as the OE Fiat fan switch? If so - I'm thinking that this would be perfect for me. I have a single fan (no AC), and I have a second fan handy (for my turbo project, to help with water to air intercooler) - I think the 95/102 would be perfect for my needs.

I already have a relay for my fan, and could easily add a second relay for the other fan - using the the VW fan switch. Perfect, and thanks once again!
 
myronx19 said:
I suppose the thread is the same as the OE Fiat fan switch?
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Yes, same thread pitch and diameter - direct fit in the original Fiat rad, any aftermarket one made for the X, or any VW rad (an optional replacement for the stock X rad). ;)

Shop around for the VW switch, as prices vary widely between sellers. But look for one that verifies the temp ratings that you want; many listings do not specify and unfortunately not all of the switches with the same part number are the same temps. As mentioned before there are a LOT of misidentified listings - I see many with the same part number but different settings/specs.
 
Dewolf said:
I have written about that fan relay somewhere else here.

2nd Radiator Fan Wiring

I hesitate to update, knowing that forum members here seem strongly to prefer doing things the Hard-But-Right way instead of the Easy-But-Wrong way... But there may be a bit of useful info in here for future browsers of this thread. I simply rewired the fans in parallel instead of in series...
xwebforums.com
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Thanks for the link. A couple questions about using the Volvo part. It appears to be essentially two standard relays in one housing? Is it any different than just using two standard relays (of the appropriate amperage)? Also, in reference to the wiring diagram in your link, why add a third relay to trigger this dual relay? Couldn't you wire the ignition switch into the low current circuit going into the Volvo relay? Lastly, it appears the Volvo relay requires proprietary connectors to wire it? Thanks for adding these details to help me understand.
 
Dr Jeff
I like the Volvo for ease really. One power in and your relays are ready to go. There isn't a low current circuit on the Volvo relay. The fans draw current through the 12V in via the relays. You can use the single relay from the ignition if you don't want fan run on after shut down. I don't use it. I wire straight to the battery using a 30 amp fuse. That way the fans will run after shut down if needed. The other bonus is, you won't noticed any alternator current draw using the battery as the power supply. Or at least I never have.
 
Dewolf said:
There isn't a low current circuit on the Volvo relay. The fans draw current through the 12V in via the relays.
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I see that now. So ya, the extra relay would be needed if you want it "switched". Thanks for the added info. ;)
 
Dewolf said:
Dr Jeff
I like the Volvo for ease really. One power in and your relays are ready to go. There isn't a low current circuit on the Volvo relay. The fans draw current through the 12V in via the relays. You can use the single relay from the ignition if you don't want fan run on after shut down. I don't use it. I wire straight to the battery using a 30 amp fuse. That way the fans will run after shut down if needed. The other bonus is, you won't noticed any alternator current draw using the battery as the power supply. Or at least I never have.
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What version thermoswitch are you using? Is it one like the ones we are discussing? I probably have half a dozen of those relays.
 
I use the VW one. Can't remember the part number but they're all pretty much the same.

I just wire up my own connectors and use heat shrink and flexible split auto conduit.
 
From Matthew Volvo website:

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Looking at the Volvo / Ford cooling fan module diagram... it does NOT appear to be a CAN signal ( pin 4 -> 64/90 -> ECM 5 cyl T, pin B:8) There is no evidence of a direct link to coolant temp, so that must be handled internally to the ECM based in input from the ECT. I don't have design&function manual for this that would explain the nitty-gritty of it all.

I can try connecting (+,-) to the module (4/71) main plug & grounding the 3rd wire directly & through some resistance to see if I can modulate the fan speed. Maybe I will need to use an Arduino to modulate the pulse?

The fan itself is about 16" OD, so no way to use that


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The Volvo controller....

IMG-20200901-091940.jpg


The Volvo ME9 EMS guru says it uses a PWM signal via the EMS. No data available, so I don't quite know how to test that. I have all the connectors

IMG-20200901-091947.jpg


IMG-20200901-092100.jpg
 
lookforjoe said:
it uses a PWM signal via the EMS
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So that sounds like the ECU actually does the controlling of fan speed (i.e. creates the PWM), and the module is more if just an interface of some sort - perhaps a variable relay? This isn't my area of knowledge by any means so I'm just trying to get the general idea of it.
 
Dr.Jeff said:
So that sounds like the ECU actually does the controlling of fan speed (i.e. creates the PWM), and the module is more if just an interface of some sort - perhaps a variable relay? This isn't my area of knowledge by any means so I'm just trying to get the general idea of it.
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That is my take on it. I don't know how to go about emulating the PWM signal, since I have no way of gathering that info/data. I can try hooking it up to my Honda EMS & see if it does anything. I think the Honda system also 'manages' the ground signal

Screen Shot 2020-09-02 at 8.11.14 PM.png
 
lookforjoe said:
I don't think it would - pretty sure they both manage the ground.
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I've been working working a lot with (Maxx)ECU lately and per my understanding you can not use a PWM signal for fans etc. -The current is to high and could destroy the ECU. Using a relay is not an alternative as it cannot handle the relative high frequency from the PWM signal (20-200Hz), and even if it could, it would wear out quickly. A transistor based relay might work? The ECU PWM signal is good for small devices and currents only, such as boost controllers, idle valves etc.
 
Bjorn Nilson said:
I've been working working a lot with (Maxx)ECU lately and per my understanding you can not use a PWM signal for fans etc. -The current is to high and could destroy the ECU. Using a relay is not an alternative as it cannot handle the relative high frequency from the PWM signal (20-200Hz), and even if it could, it would wear out quickly. A transistor based relay might work? The ECU PWM signal is good for small devices and currents only, such as boost controllers, idle valves etc.
Click to expand...

Well, that would explain the hefty controller (shown above) on the fan shroud. As shown in the Volvo and Honda EMS wiring diagrams they definitely control the fan using an internal (to the EMS) modulated ground signal, definitely no load involved on the ECU side - one can tell from the gauge wire they use for that - visible in the three-pole connector pic above. Not sure what the difference with an aftermarket EMS would be in that regard.
 
A DMOS solid state relay could work for that application. If you don't need the isolation, you could go with just a transistor and a few components.
 
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