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Old 05-14-2018, 09:53 AM   #1
105Charlie
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Default LH2.4 Running fans?

Hi,

I've converted my 343 (the little weird volvo) to LH2.4 to run the redblock turbo conversion.

I've added a couple of fans to the rad but am unsure of the correct wiring for this? I understand the ECU has low/high fan connectors but I assume these run via a relay etc etc. I should still have the old relays from the 940 loom so if I need any of that I should have it.

So I'm just after advice on the best way to wire up my fans so the engine doesn't cook!

Thanks,
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Old 05-14-2018, 09:56 AM   #2
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The ECU fuel computer will trigger the relay first low speed then high. The wires from the ECU to the relay are the grounds for the relay. Relay hooks right to the battery.
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Old 05-14-2018, 10:09 AM   #3
105Charlie
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Quote:
Originally Posted by sbabbs View Post
The ECU fuel computer will trigger the relay first low speed then high. The wires from the ECU to the relay are the grounds for the relay. Relay hooks right to the battery.
Perfect, exactly what I needed to know.

So run power to the relays, connect the low/high to the relays, connect fans to relays? Should I run one relay for each fan or can I just wire them in together?

Any chance you know what relay it is? I'm sure I can find it if not
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Old 05-14-2018, 10:53 AM   #4
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We'll the relay is the one connected to the electric fan, it's usually up close there by the battery and the radiator. It's a volvo relay, two stage made for it. Each fan? 940's have one two speed fan, it starts out at low speed then goes to high speed this is so you don't draw too many amps. If your doing something custom then do it.
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Old 05-14-2018, 09:28 PM   #5
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To run the fans, you'll need a LH2.4 ECU from a 940, and a wiring harness from a 940. The 240 harness/ECU doesn't include the 2 hi/lo fan control wires or circuits.
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Old 05-15-2018, 03:51 AM   #6
105Charlie
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I've added two fans so I'm hoping I could wire them up together, it's custom but I'm hoping to keep it as close as possible.

I've got a 940 loom and I'm running LH2.4, not sure where you got 240 from
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Old 05-15-2018, 01:38 PM   #7
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You can always just add the two wires from the ECU to the relay if your LH harness doesn't have them. Yes you do need a 9xx ECU to run the fans also. Thos 5xx ones don't do it. Also a 951 don't do it, needs to be like stated the later 940 ECU's, the nine ex-es.

Yeah just wire both fans to the relay should work as long as it's not too much of a power draw on the relay and melts it. Should be fine, the stock 940 fan is one big one, so if your running two they must be smaller.
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Old 05-15-2018, 08:09 PM   #8
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Quote:
Originally Posted by bobxyz View Post
To run the fans, you'll need a LH2.4 ECU from a 940, and a wiring harness from a 940. The 240 harness/ECU doesn't include the 2 hi/lo fan control wires or circuits.
Boo hiss. I was going to get this upgrade underway. But will the 940 ecu run a 240 2.4 ?
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Old 05-15-2018, 11:08 PM   #9
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I looked at some wiring diagrams and it's not so clear cut. The '91 940 runs the fans off the A/C relays, not the ECU. The '92 940 wiring diagram shows ECU pins 10&11 running the fans. I have a ...937 ECU from a '92 940 that has the fan circuits and, as sbabbs mentioned, I have a ...951 ECU from a 240 without fan circuits. The 940 LH2.4 ECU will run a 240 (assuming that the ECU doesn't include an immobilizer).
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Old 05-16-2018, 03:55 AM   #10
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If you are intending to use the Volvo 940 relay be aware that when the high speed fan circuit cuts in, it disconnects the low speed fan circuit, which would be no good if you have one fan connected to each. You would end up with only one fan running at any one time.
The best solution is to common the two output wire from the relay together and use them to run both fans at the same time whether the high or low speed circuit is active.
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Old 05-23-2018, 08:31 AM   #11
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For my 2 speed fan I am just installing a BMW 2 speed fan switch and using the volvo relays along with the oem wiring harness.

Only thing special needed is an inline coolant adapter for the switch plus a bmw dual temp switch and wires.

http://www.therangerstation.com/tech...tric_fan.shtml
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