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_ HalfDork
6/22/19 9:34 p.m.

Obd2 na8. Stock ecu. So I’ve read a few different things now after my original thread. One thread said the the passenger side fan should come on at 96 degrees... that can’t be right. Another thread said 207°. That sounds more like it. According to my dongle, my fan is kicking in around 225°. And I can see there would be a difference between temps since the two sensors are in different places on the motor. 

What I can’t understand is if the AC fan (driver side fan) should be on 24/7 if the AC is activated. Because it’s not. I turn on the AC, no fan that I can see, but I haven’t waited forever to see if the fan is supposed to cycle.  A little further research shows BOTH fans should activate when AC is on... I don’t get anything like that... so probably a bad relay?

freetors
freetors Reader
6/23/19 8:02 a.m.

Maybe they meant 96* C? That's about 205*.

Knurled.
Knurled. MegaDork
6/23/19 8:10 a.m.

A/C fans usually only kick on when the pressure is high enough to warrant it.   Would have to check the books when I get back to work on Monday.  Alternatively, with simple systems, the fans kick on when the compressor is engaged.  If the compressor isn't kicking on, the fans wouldn't either.

 

Either way, if the A/C was functioning and the fans weren't on, it'd hit blowoff pressure very quickly and you'd have most of the refrigerant blow out of the safety valve.  So, there are one of three things that are happening:  The A/C pressure is too low to warrant the fans coming on, which means you need A/C service.  The compressor isn't being commanded to engage, which means you need A/C service.  Or the fans aren't engaging and the A/C used to work and now it blew all the refrigerant out, in which case you need A/C service....

NickD
NickD PowerDork
6/23/19 9:45 a.m.

I know on my NA, even with the AC ripped out, hitting the AC button kicked it on. Or if coolant temp hit 230 degrees, I believe. I ended up hooking the AC fan into the main fan instead and now they turn on together. 

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_ HalfDork
6/23/19 9:50 a.m.

In reply to Knurled. :

Dude, say what? The refridgerant charge has nothing to do with the AC fans kicking in. The AC works just fine. The compressor kicks in, it blows really cold air (for a miata). That entire fan system is operated electrically, meaning when the ac button is pressed, and ac fan relay is closed, and voltage is applied to (supposedly) both fans. Neither fan comes on when AC is activated. However, the passenger fan operates on/off on its own, when temps reach a certain amount. This indicates the passenger fan is good. Since both fans should be running when ac is on, I’m going to say I have a relay issue to check out. Either the Ecu isn’t grounding, or the relay is bad. (Could be bad wires, but I would doubt that on the fan side of the relay, since the one fan is still working.)

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_ HalfDork
6/23/19 9:52 a.m.

In reply to NickD :

That’s what I want to do here. Have both fans running anytime the system gets hot. Supposedly, according to a lot of ancient forum conjecture, if you straight wire the two fans together, it’ll blow a fuse. I might have to break out the wiring diagrams here. 

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_ HalfDork
6/23/19 9:53 a.m.

In reply to freetors :

Ya know, I thought that too, but the guys location was Texas, and I said to myself “uhh, no. That can’t be right.”

sergio
sergio Reader
6/23/19 10:00 a.m.
_ said:

In reply to freetors :

Ya know, I thought that too, but the guys location was Texas, and I said to myself “uhh, no. That can’t be right.”

Maybe he forgot a 1 before the 96

NickD
NickD PowerDork
6/23/19 10:01 a.m.
_ said:

In reply to NickD :

That’s what I want to do here. Have both fans running anytime the system gets hot. Supposedly, according to a lot of ancient forum conjecture, if you straight wire the two fans together, it’ll blow a fuse. I might have to break out the wiring diagrams here. 

I've been running mine like that for a year and have yet to pop a fuse. Have yet to see the coolant gauge go above operating temp either, and I beat the he'll out of my car and have a Rotrex blower generating heat

Knurled.
Knurled. MegaDork
6/23/19 10:26 a.m.
_ said:

In reply to Knurled. :

Dude, say what? The refridgerant charge has nothing to do with the AC fans kicking in. The AC works just fine. The compressor kicks in, it blows really cold air (for a miata). That entire fan system is operated electrically, meaning when the ac button is pressed, and ac fan relay is closed, and voltage is applied to (supposedly) both fans. Neither fan comes on when AC is activated. However, the passenger fan operates on/off on its own, when temps reach a certain amount. This indicates the passenger fan is good. Since both fans should be running when ac is on, I’m going to say I have a relay issue to check out. Either the Ecu isn’t grounding, or the relay is bad. (Could be bad wires, but I would doubt that on the fan side of the relay, since the one fan is still working.)

I did say that I'd have to check.  Generally (as in generally for cars with electric fans) the fans only run when the compressor is engaged, or the pressure is high enough to warrant it.  With an extremely simple system that controls the compressor clutch with an evaporator temperature switch, the compressor and fan will run even with a completely discharged system (as NickD points out happens on his car)

 

Since you already know how it works and what the problem is, what is your question?

ChasH
ChasH Reader
6/23/19 1:23 p.m.

Drivers side fan is the primary cooling fan and comes on ~207 F, passenger side is the A/C and secondary cooling fan, coming on at ~225 F. Both fans should run when the A/C is on. Typical problem is the connectors to the fans over heating and melting. Or someone made some modifications or repairs that are questionalbe or no longer working.

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_ HalfDork
6/23/19 3:39 p.m.

In reply to Knurled. :

I meant no disrespect. I did more research on the topic over the night. What I really want to know is if both fans should be turning when ac is kicked on. That gets me started on diagnosis. The forums say two different things, but I think there is always a problem due to there being two completely different systems between na6 an na8. The replies contradict each other, and I believe these people think all the systems are the same. 

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