Radiator fan circuit issues

ASSISTANCE Electrical & Entertainment Systems
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Radiator fan hasn’t came on on its own ever since i did my b20b swap in april 2008. i had to extend the wires that go to the ECT bcuz of the B20b. i don’t think i have an engine oil temp switch… cuz i was looking and found that 2 wires on the harness weren’t going to anything. i’ll have to take a closer look but i’m pretty sure my block didn’t have one. i’m thinking of getting the oil filter adapter plate and installing the switch onto that so we’ll see on that part.

  • i’ve tried jumping the ECT switch connector while the car is “ON” not running = fan doesn’t come on.

  • With car still ON not running, i’ve disconnected the radiator fan relay and checked it by grounding terminal D and i got the fan to turn on. so i thought it was the relay… and i replaced that at a local parts store $53. didn’t solve my issues.

  • with the new relay installed, and the car on… i tried jumping the ECT connector again, still nothing. i believe i should check continuity of the wires to the ECT. Will check again tomorrow

i’m thinking a decent possible solution, (not the best), is to rewire the relay and the ECT. i might have an open somewhere along the harness but finding that would take some time. so on the ground wire for the ECT i’d hook it up to a ground, then the other wire (yellow/green) i’d hook that up to the relay… I’ve found that Terminals A, B, and C all have power. so i’d hook the yellow/green from ect to terminal D on the relay? cuz when i put Ground to terminal B i get the condensor fan to come on. cuz A & B have continuity when C has power and D has ground right?

so basically i’m switching out the yellow/green wire thats on the relay… extend that all the way to the ECT and cut and splice it onto the yellow/green wire on there. then take the black wire and find myself a decent body ground. that sounds good and logical right?

Cooling fan relay.jpg
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The 4 wires of the rad fan relay are…

1- Black, ground at all times, [A or B of relay] relay input.
2- Blue, to rad fan, [A or B of relay] relay output.
3- Black/yellow, 12V+, [hot when ign. is on ] relay power.
4- Yellow/green, ground trigger from ECTS.

The rad fan relay supplies the rad fan motor with a ground when the ECTS closes, [at about 190 degrees] and supplies the relays coil with a ground.

There should be only one “true” 12V+ at the relay, the switched black/yellow.
A test light/meter would also show 12V+ on the blue lead when relay is off, it is the 12V+ on the other side of the load, [rad fan motor] you could also get a 12V+ reading on the black at the relay if relay was energized, [on] and the black lead was not grounded.

So I understand correctly, if you turn on the ign. and then ground the yellow/green, [terminal D] lead at the relay plug, [with relay plugged in] the rad fan works, is that correct?

Confirm that the wire colors at rad fan relay plug are as stated above.
Doing anything, [grounding terminal B] at the rad fan relay should not turn on the condenser fan, it would do absolutely nothing if terminal B is the black lead, [ground] or it would turn on the rad fan if terminal B is the blue lead. [ground for rad fan motor].

You are sure you have the rad fan relay, [mounted to rad support just in front of batt.] right?

Although when A/C head pressure is high enough to trigger the condenser fan relay it will also trigger the rad fan relay, both fans are used for A/C condenser, when ECTS triggers the rad fan relay it should not trigger the condenser fan relay, only rad fan is used for radiator

Your USDM G2 stock engine did have an “Engine Oil Temperature Switch”, [unlike the CDM G2s that did not] it appears the B20b also does not have the EOTS but I assume you could add one, if the ECTS plug is there, [2pin plug, black and green/white leads].:corn:94

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thanks fcm. well i followed all that mentioned and felt that i did EVERYTHING right and that all was where it should be. but i wasn’t getting ground at yellow/green. so i traced the yellow/green wire from the ECTS and well… i decided to give it a try by switching it with what i thought was the EOTS. yellow/green looks a lot like white/green when they are both dirty. so i switched them around… turned the car to the ON position, jumped the ECTS connector plugged in my old relay and VOILA!!!

WORKS!!! only issue is that i believe i had the grounds backwards too… so the condensor fan was coming on with the radiator fan.

so i believe i was giving the consensor fan a short to power then right? so i unplugged the condensor fan and will swap around the 2 ground wires tuesday when i put it on a lift, to make it a lot easier to access the wires.

thank u very much tho fcm. but you were right, double checking the wires on the relay to make sure that they were right n stuff helped out a lot. i was just looking at it differently. and i dunno how i got power to come out on terminal a, b, and c yesterday. might have been too much of that dielectric grease on it or something. but all is good now except for the condensor fan.

i gotta get it up and running properly cuz i’m reinstalling a/c. :slight_smile:

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Remember, the rad fan relay supplies the rad fan with a ground, 12V+ is constant at the fan, on the other hand the condenser fan relay supplies the condenser fan with 12V+, ground is constant at the fan.:whisper:94

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so my condensor fan came on bcuz i supplied it with a ground from the module then correct? cuz from what i can see, and from what i’ve learned in the electrical classes… is that… since i used the EOTS black wire as my ground for my ECTS… i got both to work, since both have 12V. both circuits were just looking for a ground. and me here, supplying the ground… thru the ECTS… which in turn i shared with the EOTS makes it both come on.

long story short… if i switch the ground wires that i mixed up with the ECTS and EOTS… all should work normally and fine afterwards correct FCM?

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Maybe, :dunno:94

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lol. got it. thanks fcm.