2003 Volvo c70, I swapped the motors in this car because he blew up the motor, I think it blew up because it got to hot. New motor is in but the fans

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#1
Make
Volvo
Model
C70
Year
2003
Miles
120k
Engine
2.4 turbo
I replaced the temp sensor and fan relay but fans don't come on unless I disconnect the temp switch. The won't come on with air conditioner either.
 
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#2
May not come on until ECT reaches a preset temp.
Need to find out if AC commands fans OR no fan until a preset High psi.

The fact the disconnected temp switch causes fan shows PCM is controlling the fans.
Time permitting I will check volvo 'logic' and repost.
 

nickb2

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#3
From memory, fan comes on @ 205f or so. It is a turbo, they run hot.

If you have any form of reading live data, that would help. If you see the engine @ 205ish and fan not coming on, and also the AC on, no fan, that circuit has a problem. Removing the temp sensor from the circuit tells us the PCM is seeing that, so that portion of the circuit is also fine.

This will go south soon.
 

nickb2

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#4
Also, removing the temp sensor, you must have had the key on and or engine running. I think the PCM should have seen that right away and stored a pending circuit code at the very least.

Here is a wiring of this circuit. Study it, and also tells us if you can get live data. Try checking the relay on shroud, it is a double relay, probably for two speed functionality such as ac and when engine is hot, it will go into second speed/high. Obviously one of those relays is working since fan turns when temp sensor disconnected, so this is maybe a pcm problem at this point.

Then again, vovlo logic will maybe have coded that also. Question I have not asked, duh!! Is check engine light on?
 

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nickb2

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#5
Proof of what I meant in above reply about relays and maybe this being a pcm problem if all wiring is ok, new sensor, fans turning when temp sensor disconnected is very much going quickly to a fried pcm, especially knowing where it is located, in the wheel well lining, much like mopar loved to do on this era car. It was a new time, saving of wiring, moved pcm closer to battery. Screenshot (31).png
 

nickb2

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#6
Try grounding the yellow wire at fan relay block on shroud, it will run low speed or vice verca, I can't remember which one does what speed, then ground the yellow and white wire, it should turn fan also, if that works, relay block is good, fan is good. \then pin test those yellow wires to pcm, if they are good, then only thing left is ecm/pcm if those fan relays are not coming on @ 205f ish.