If you’re talking about my swap…the lack of the oil temp switch did not cause a CEL for me.
That is correct, the ECU will not throw a code for the Oil Temp switch. It’s purely used by the radiator fan control module to turn the fan on when specified.
collin, thanks for making this thread. very big help!
ditto, thanks colin. this has been a huge help, i wish i could say the swap runs now because of this thread. (it wont fire up, fuel issue, nothing due to your article)
but this wont cause an open circuit and not turn the fan at all, right ???
I dont believe that is correct… Though Colin would know with more certainty than I.
Correct, it won’t prevent the fan from working normally when the ECT switch tells it to. The engine oil temp switch has two wires, one of them leads to ground, the other leads to the RFCM. When a certain temp is reached the switch closes the circuit between these two wires, thus connecting the RFCM to ground and indicating that the fan should be turned on. If you disconnect the switch the RFCM will just always think the oil temp is OK and the fan shouldn’t be turned on. But it will still be able to receive the proper signal from the ECT switch and turn on when the coolant temp reaches a certain point.
ok well i replaced my coolant temp sensor on my 91, the one on the cylinder head next to the sending unit. But my radiator fan doesnt turn on, it only comes on with my a/c. Does this mean i need to replace the ect on the block?
Read the first post in this topic. I explain the purpose of both the ECT sensor and ECT Switch. The ECT Sensor has nothing to do with your radiator fan, so replacing it will not fix a radiator fan problem.
Colin-
You explained how the Rad fans turns on and off on certain temps. My question is, what about the “condenser” fan? When or what does this fan turn on to? And what switches is this fan related to?
Good info hear, but still lost. Just swapped in a b20v and the fans wont kick on. Checked all connections , replaced the radiator fan switch and thermostat. Switched over to obd1 with rywire conversion harness. Still wondering why the fans still wont kick on and dont want to wire them to always stay on. Any help would be great.
You’re going to have to start fresh with wiring, you sorta started in the exact wrong place. You likely did not need a new fan switch. If you’re using a Rywire harness, that means you’re looking for simplicity and cleanliness. If that’s the case then you want to just re-wire the fan system and do away with the radiator fan control module. Unfortunately I don’t have time for a full answer right now. How familiar are you with car electronics? It’s pretty simple stuff really. If you look at your Helms, what you’ll want to do is change the wiring to mimic a Canadian G2 w/o AC. That’s the most simple way to go. If you still need help just reply to this post so I am reminded to come back later with some more comments.
Bump: I couldn’t help but notice that a lot of people are having difficulty with this ect switch or sensor. To make it easier for everyone you can take out your old ect sensor or switch from your old block the green one that plugs in to a connector Not the headphone type single connector that has a two individual connectors going into one sensor no not that one I’m talking about the off green sensor that looks like a knock sensor yeah that’s the one I’m referring to. So go to your newer engine block and pop loose that closed allen type bolt or whatever is called that looks like a knock or some type of sensor used to be in it’s place and put the ect sensor from the older engine in it. It will fit inside perfectly and you can now plug in your green connector from your wiring harness and BAM. There you go, no more overheating and now your fans should come on. Now this was done on my 92 da that had a ls motor and I went with a 99 b16a2 engine and at first my cooling fan wouldn’t come on so I though it was the cooling switch on the thermostat housing and no still no fans so I dug up more info and traced the wiring and the end result was to utilize my old ect switch and just leave it hanging bit that wouldn’t work so I though hmm maybe this should be going in to the block so I used a allen type socket and broke that sucker loose and transferred in the ect from the older block on to the newer one. So then I plugged it in to the harness and my fans mind that I have ac came on and I was relieved but not certain till I took it for a test drive to see if ran hot and it didn’t, not after that. I hope this helps the needy and I apologize for my grammar and if I misspelled something. Let me know if you have any questions regarding this.
Colin,
You are forever helping me and you have no idea haha. You wrote this 4 years ago and it was just the info I needed to figure out why my B18b block wasnt kicking fans on.
Apparently, the EOT is the exact same pigtale and the Thermohousing Switch. I thought that was what I needed to extend and low and behold it was the goofy connector at the back of the block.
So for anyone swapping a 2nd gen B series, the odd two separate pigtale at the rear is your ECT, NOT the green pigtale, which is EOT.
If I ever meet you, I’m buying you a beer haha.
[QUOTE=91akira;2202463]Colin-
You explained how the Rad fans turns on and off on certain temps. My question is, what about the “condenser” fan? When or what does this fan turn on to? And what switches is this fan related to?[/QUOTE]
Fixing my AC and this is a good question as I have my rad fans wired to be on all the time.
^Honestly, I have no idea, I removed all my AC stuff 
However, your Helms manual should have all/most/some of that info. If I had to guess I would think a lot of the stuff you guys are asking about is dealt with by the “Radiator Fan Control Module”.
EDIT I just took a quick look and there’s TONS of info in the Helms, chapter 22 is dedicated completely to the Air Conditioning system. If you read through the troubleshooting procedures and explanation of the system it should be pretty straight forward.
[QUOTE=Colin;2299576]^Honestly, I have no idea, I removed all my AC stuff However, your Helms manual should have all/most/some of that info. If I had to guess I would think a lot of the stuff you guys are asking about is dealt with by the “Radiator Fan Control Module”.
EDIT I just took a quick look and there’s TONS of info in the Helms, chapter 22 is dedicated completely to the Air Conditioning system. If you read through the troubleshooting procedures and explanation of the system it should be pretty straight forward.[/QUOTE]
Thanks for the info! I gotta stop being lazy and buy a Helms.
Yeah, Helms is mandatory, you shouldn’t even be working on your car without it! 
On another note, shoot me an email, I have a question for you and your email isn’t listed in your profile.
Emailed