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Old 12-02-2018, 11:17 PM   #1
BLACKMAYO
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Default Radiator temp switch(for ac) Efan conversion

Hi bricks fans, im about to do an e fan conversion on my 740t 91 i was hoping to have an answer about the temp switch for a dual speed fan. Can i use the switch on top of my radioator and if its a dual speed? Volvo pn 1274962 thanks!
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Old 12-02-2018, 11:37 PM   #2
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That's the 'it's way too hot turn on the AC pusher fan switch'.
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Old 12-03-2018, 09:02 AM   #3
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So can i use the switch for a two speed e fan comversion?
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Old 12-03-2018, 09:11 AM   #4
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No. It's a single-speed switch, and goes on way too high.
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Old 12-03-2018, 09:48 AM   #5
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Originally Posted by BLACKMAYO View Post
So can i use the switch for a two speed e fan comversion?
Depends how how you like your coolant.
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Old 12-03-2018, 10:30 AM   #6
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okay thanks, but the 940 came with an e fan. In that case they were only one speed? or the ecu control the two speed signal?
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Old 12-03-2018, 12:21 PM   #7
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Originally Posted by BLACKMAYO View Post
okay thanks, but the 940 came with an e fan. In that case they were only one speed? or the ecu control the two speed signal?
LH2.4 940s control the fan with the ECU
Regina 940s control the fan with:
a) low speed is triggered by a pressure switch in the ac condenser and only comes on when ac is on and pressures reach x psi.
b) high speed is triggered when the radiator temp switch contacts close, around 230F.

Far too hot IMO. Plenty here will tell you 230F is an acceptable temp for iron block aluminum head engines but I beg to differ. My hypothesis is that volvo gave the 940s a massive radiator and let convection do the job and that the high speed trigger was only used as an overheat switch. You must idle for 5+ minutes for that high speed to come on in a 940 with the big rad on a hot day. So most of the time temps don't get that high unless you're idling. Different story in a 2/7 series with the smaller radiator. Temps will rise much faster and you will see 230F temps more regularly. Sure, it'll work, but volvo had their engines running under ~195F for how many years? Then all of a sudden upped the temps, probably for fuel economy and efficiency reasons.

To each their own. Pretty positive the engine will last longer running at 200F or less than it will at 230F. Simple physics. Higher heat causes expansion and iron and aluminum expand at different rates. The more they expand at different rates, the more 'scrubbing' that takes place and the faster the HG will fail. And heat = pressure, and pressure = failed cooling systems. They DOUBLED the operating pressure in 7/9 cars in comparison to the 240s, and it is dumb. Unless you like doing heater cores in volvos. We all know the 7/9 heater control valves fail too. They ALL fail earlier than they should. Wonder why I constantly see 940s with blown HG. They start leaking coolant, then stupid volvo and their stupid fake temp gauges do absolutely nothing, so people keep driving them without checking fluid.
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Old 12-03-2018, 12:39 PM   #8
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Quote:
Originally Posted by PromiseRing View Post
LH2.4 940s control the fan with the ECU
Regina 940s control the fan with:
a) low speed is triggered by a pressure switch in the ac condenser and only comes on when ac is on and pressures reach x psi.
b) high speed is triggered when the radiator temp switch contacts close, around 230F.

Far too hot IMO. Plenty here will tell you 230F is an acceptable temp for iron block aluminum head engines but I beg to differ. My hypothesis is that volvo gave the 940s a massive radiator and let convection do the job and that the high speed trigger was only used as an overheat switch. You must idle for 5+ minutes for that high speed to come on in a 940 with the big rad on a hot day. So most of the time temps don't get that high unless you're idling. Different story in a 2/7 series with the smaller radiator. Temps will rise much faster and you will see 230F temps more regularly. Sure, it'll work, but volvo had their engines running under ~195F for how many years? Then all of a sudden upped the temps, probably for fuel economy and efficiency reasons.

To each their own. Pretty positive the engine will last longer running at 200F or less than it will at 230F. Simple physics. Higher heat causes expansion and iron and aluminum expand at different rates. The more they expand at different rates, the more 'scrubbing' that takes place and the faster the HG will fail. And heat = pressure, and pressure = failed cooling systems. They DOUBLED the operating pressure in 7/9 cars in comparison to the 240s, and it is dumb. Unless you like doing heater cores in volvos. We all know the 7/9 heater control valves fail too. They ALL fail earlier than they should. Wonder why I constantly see 940s with blown HG. They start leaking coolant, then stupid volvo and their stupid fake temp gauges do absolutely nothing, so people keep driving them without checking fluid.
This may be a dumb question powered by inexperience, but can you just swap the larger 940 radiator into the 740 and solve the problem?
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Old 12-03-2018, 02:49 PM   #9
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This may be a dumb question powered by inexperience, but can you just swap the larger 940 radiator into the 740 and solve the problem?
I wouldn’t consider it solving the problem. Afterall, what volvo did was really just a band aid.

I believe the radiator itself might fit, Idk? But it is physically taller as well. So the lower tax support may be different. You’ll have to search. Also, the wide ness of the rad will interfere with the NA airboxes I think. Again, gotta search cus I’m just guessing.
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Old 12-03-2018, 03:10 PM   #10
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You could swap the front clip and it would bolt up.
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Old 12-03-2018, 03:34 PM   #11
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Quote:
Originally Posted by PromiseRing View Post
LH2.4 940s control the fan with the ECU
Regina 940s control the fan with:
a) low speed is triggered by a pressure switch in the ac condenser and only comes on when ac is on and pressures reach x psi.
b) high speed is triggered when the radiator temp switch contacts close, around 230F.

Far too hot IMO. Plenty here will tell you 230F is an acceptable temp for iron block aluminum head engines but I beg to differ. My hypothesis is that volvo gave the 940s a massive radiator and let convection do the job and that the high speed trigger was only used as an overheat switch. You must idle for 5+ minutes for that high speed to come on in a 940 with the big rad on a hot day. So most of the time temps don't get that high unless you're idling. Different story in a 2/7 series with the smaller radiator. Temps will rise much faster and you will see 230F temps more regularly. Sure, it'll work, but volvo had their engines running under ~195F for how many years? Then all of a sudden upped the temps, probably for fuel economy and efficiency reasons.

To each their own. Pretty positive the engine will last longer running at 200F or less than it will at 230F. Simple physics. Higher heat causes expansion and iron and aluminum expand at different rates. The more they expand at different rates, the more 'scrubbing' that takes place and the faster the HG will fail. And heat = pressure, and pressure = failed cooling systems. They DOUBLED the operating pressure in 7/9 cars in comparison to the 240s, and it is dumb. Unless you like doing heater cores in volvos. We all know the 7/9 heater control valves fail too. They ALL fail earlier than they should. Wonder why I constantly see 940s with blown HG. They start leaking coolant, then stupid volvo and their stupid fake temp gauges do absolutely nothing, so people keep driving them without checking fluid.
thanks for that reply mate! i think im gonna go with the BMW 80 / 88* C (180/195*F) dual temp switch P/N 61318361787 for my efan dual speed setup!
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Old 12-03-2018, 08:43 PM   #12
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Originally Posted by BLACKMAYO View Post
thanks for that reply mate! i think im gonna go with the BMW 80 / 88* C (180/195*F) dual temp switch P/N 61318361787 for my efan dual speed setup!
Thats what I ended up doing.

Bought one of these

https://www.ebay.com/itm/BLUE-Water-...4C8p:rk:4:pf:0

Then just drilled and tapped it for the BMW sensor.
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