i have a 92 TA with a 305 TPI
i have the Dual Fan setup
my car will warm upto 220 and around 230 mark the primary fan turns on
but whenever the AC is turned on the secondary fan wont turn on
i tried 3 different relays, and i even jumpered it at the relay and it worked so i know the motor is good
any ideas?
is it one of the sending units that bolts in the engine?
thanks
Joe

 

they second fan, to my knowledge, only turns on when the motor reaches a certain temp, like 234 or something, AND when the AC pressure it at a certain level WITH the AC on. So it doesn't come on that often. Also the coolant sensor that is on the passenger side head I believe is the one that controls that fan, and could be bad, It's a coolant temp switch. I eliminated all that, and wired the primary fan relay into the secondary fan relay so that when the primary fan came on it turns both on together. Helps with the cooling a TON.

 

How good is your air conditioning working? If you're low on refrigerant, the secondary fan won't build up enough high side pressure to actually activate the fan. Any shop should be able to hook up a high side A/C pressure gauge for nothing and check the pressure for you. I'm not saying 100% that that is your problem. But if you are low on refrigerant, that would explain it.

I switched to the 200/185 fan switch just to see if the secondary fan actually worked on my car. Prior to that, the car just never got hot enough for it to kick on. Once that primary one kicks on, it cools the motor when you're at the stock 1st fan turn on point.

You might want to poke around my signature.

 

The secondary fan doesnt come on until something like 243* and I believe it is controlled by the ECM. On some camaros it comes on when you turn it to a/c and others it doesn't not sure why.

Reid Flemming i think you are confused. The radiator fan doesnt build up high side pressure in an ac system. I think you are confused with the compressor. If it was low on refrigerant the compressor would not turn on, the pressure switch is on the accumulator which is on the low side. Though this makes me wonder if the secondary fan will only be activated when the compressor is running not just if you turn it to a/c.

 

the secondary fan is controlled by a thermo switch located in the passenger head connected through the ac system. If the ac system doesn't have enough pressure AND the temp is not high enough, the fan will not activate, it needs BOTH pressure and temp to activate, and doesn't come on very often. The driver's side fan is the only one controlled by the ECM, and is the primary fan. I have my relays wired so that when the primary fan turns on the passenger fan comes on as well, makes life much easier.

 

ok so the primary fan is ecm controlled and the secondary fan is controlled by a thermostatic switch in the head and by the a/c pressure switch.

So that brings the question is his a/c system empty?


I have my primary fan on all the time and the secondary is on a toggle. I would like to come up with a better system for it using a thermostatic switch in the head to turn them on.

I think there is a lot of ways to skin a cat on this one. I think your idea of wiring them both on when the ecm turns the primary on is good too. I'm just worried that turning them both on at the same time puts a bigger strain on the alternator. But then again it would cool the radiator off faster and be on less.

 

it's not too bad on alternator....sometimes the both fans come on together from factory anyway. I think the fans pull like 15 amps each and a stock alternator is capable of like 90 amps. I don't even have a problem with mine co ming on together. The switch idea works good, have done that on another camaro. Also, a few companies make a thermostatic switch that activates at a lower temp...like 190 or 185 or something. If you were to bypass the a/c part of the wiring and just have the thermo switch activating the fan using the lower temp setting, then it would turn on/off on it's own with or without the a/c and at the right temp. I know JET makes a switch that turns it on lower.But running them both together off the ecm seems to work the best...you get the exact tempature your shooting for and they don't stay on very long at all.

 

Driver side (primary) fan turns on when
a) ECM says it's at turn on temp (223°F)
or
b) Air conditioning is turned on.


Passenger side (secondary) fan turns on when
a) fan switch in cylinder head is reached. Stock fan switch is 235°F
or
b) A/C high side pressure hits 233 psi.

On an air conditioning system that is slightly low on charge, you'll get rapid compressor cycling (on-off-on-off). This is the low pressure side (measured at the accumulator schraeder valve) dropping like a rock every time the A/C is cycled on, due to the low charge. If you look at it with gauges, it will turn on around 45 psi and then very quickly shoot down to 26 psi. Shut off. Rise back up to 45 psi.........

When you're low on refrigerant and getting rapid cycling, the high side won't build up enough pressure (heat rejection to the condenser) due to the system not running for long enough.....So the end result will be the A/C cycles way too often while the passenger fan stays off. Driver side fan will be on though. Even when the A/C is cycling like that, there is a certain delay on the driver side fan. If I were to start my car up cold and turn on the A/C for 20 seconds, then turn the A/C off, I could walk over to the hood and see the fans stay on for (guessing) 15 seconds or so. Even though the coolant temp may be 100°

In colder months, when you run the defrost, the passenger fan may not come on with the air conditioning because it's so cold outside that the condenser simply sucks the heat out of the high side too fast for the heat (high side pressure) to build up to 233 psi.

An interesting thing about the fan switch in the cylinder head is that it will also turn on the primary fan if it isn't already on. In my car, with the stock ECM programmed primary fan turn on (223°) and a 200° fan switch, both fans will turn on at 200°.

 

You are correct about the (low) pressure switch on the accumulator. That is on there to shut the system off (cycle off) when the right temperature has been reached. Keeps the system from icing up.

The pressure switch is adjustable, although for most people it's set at the proper point already. Stock on my car is 26 psi. People who do R-134a conversions will often adjust it down to around 22 psi in order to get a bit more cooling out of R-134a before it cycles off. If R-12 and R-134a are at the same pressure, R-134a will be warmer. Hence why people turn R-134a low pressure cycle psi down a few psi.

If it's 40° outside or colder, running the defroster won't turn on the compressor (or the fans for that matter). That's because the low side pressure will never get high enough (45 psi) to turn on the compressor. 40° ambient air is equivalent to 26 psi give or take. Same reason why R-12 will shut off the compressor at 26 psi while blowing 40° air into your interior.

But that pressure switch has nothing to do with the high side pressure. The high side pressure goes up when the A/C is running. The passenger fan turns on when the system builds up enough pressure to warrant it coming on.

Now if your passenger fan truly is not working like it's supposed to. You'll see the high side pressure shoot past 300 psi. Air conditioning performance will suffer as well. Air conditioning isn't about creating cold air. It's about removing hot air. A great example is a fridge at home. It doesn't create cold air inside. It simply absorbs the heat inside and then sends it outside to your kitchen. All that's left over is cold inside the fridge.

 

Either will turn on the passenger fan. With a fully charged A/C system. Starting the car (let's say 160° coolant temp) and turning on the A/C will make the passenger fan turn on. It doesn't take much to get the high side to 233 psi.

233 psi on an R-12 car is aprox 145-150°F at the condenser.

My car idling with A/C on in the summer time after it's sat for a few hours, will run 35 psi low and 235 psi high. Both fans are on. Coolant temp is 120-180° (depends on how long it's sat)

 

How does ECM know that temp is high enough to turn on the primary fan? where is the sensor? does it use the data sent by the fan switch in the pass head? I guess the question is how can I keep primary controll by ECM and have it be turned on at a lower temp for better cooling? Or more to the point , will the 200* Jet switch also turn on primary at lower temp as well as secondary at the same time?

 

primary fan is turned on by the ecm,the ecm reads the coolant temp sensor,and depending on the temp in the prom,requests the primary fan.

i have both fans wired as primary.works great,nice fast cool down,and the a/c loves it.been that way for 3 years.

 

but I already got the Jet switch ;-(

 

that sucks,sell it on ebay or here.
you need a new prom to lower the fan temps

 

Yes.

 

Thanks. I put in the new Jet switch (185) but the pass side fan still does not come on when the car heats up to 200. The driver side fan on the other hand runs continuously as soon as I start the car even when its cold... I have tested the pass side fan, I know its not the motor. Any ideas? Thanks!

 

Start running through the tests in my sig.

 

thank you!

 

Most people will probably say this is ghetto, but it works. Wire your second fan to your first. I never understood the concept behind two fans at different temps, why let it inevitably get hotter and hotter. Both of my fans come on at roughly 200 degrees and it cools my engine right off, and when I turn on my ac both fans kick on. I run 195 to 200 all the time. I wire it nicely, and routed it properly. You can even use an inline fuse if your worried about something happening. I have had no issues though.

 

Very informative, Reid Fleming.