Hey everyone, i have a 1988 trans am gta (350CID) with a 195 thermostat in the cooling system. Recently i went for an emissions test (it's the last year i need one) and blew a rad tank off the rad. The old radiator was fairly old, and was leaking very slowly at the top of the driver's side tank (dripping), but it blew out at the passenger side. i changed the hoses and radiator afterwards and noticed that one of the fans wouldn't move when power was applied to it, so i've changed it out. The problem is, the fan still won't move even when temperatures get real hot (about 120 celcius, or 248 farhenheit). I've tested the circuit and there is power going to both fans' plugs and the relays work fine, both fans move when power is directly applied.
I'd like to know where the secondary cooling fan switch is located, and when should it be coming on? i don't want to take it for another e-test to have the rad blow again. Also, do you think the two cooling fans are enough to have during a 5 minute-long emissions test done at 40 km/h (roughly 25 mph), running constant for 5 mins? Thanks for your help, any suggestions are greatly appreciated!

 

The switch should be located just above the starter. Right under where the spark plugs are mounted. You'll probably only be able to see it underneath. I have an 88 IROC 350 and that's where mine is. Be advised I changed mine out thinking it was why my secondary fan wasn't coming on. It didn't help. I am thinking maybe the vehicle isn't getting hot enough. I'll find out when the weather gets good and hot. The part costs $40 at the dealer. I applied ground to the plug per the service manual and the fan ran. According to the manual, if that is the case then you should replace the switch. Like I said, to this point it hasn't helped. I swapped my relays and that didn't change anything either.

Can I ask if your A/C is charged and working? Does the fan come on when the AC is on?

 

My AC runs, but it doesn't get cold (don't think it's charged), but you can see and hear the compressor running. No, the fan does not come on when the AC is switched on, i had it going for about 10 mins and the fan didnt budge.

 

See, that's the same thing mine is doing. I'm not sure if they A/C falls below a certain charge that the fan won't run. I think it might be controlled by A/C pressure. I won't know til i charge mine. I am waiting for the weather to get good and warm just in case I have a leak. If the leak is slow enough, I'd like to make it through the whole summer so, I don't want to charge too early. If you charge yours let me know.

 

If there is enough charge for the compressor to run, the Secondary fan should start as well.

The fan pressure switch closes at 232psi (1600kPa). The fan switch will turn the fan on at, or above 238°F (114°C).

Don't take the factory gauge as absolute either... they are more of a general temperature accurate.

 

True. But whether it turns on or off with the A/C depends on how much refrigerant is in the system. When I had 1.8 lbs of R-12 in my car, the passenger fan wouldn't turn on with the A/C. With the full amount (2.25 lbs), it turns on right away.

Stock fan switch doesn't turn on until about 235°F. Too high in my opinion. Put a fan switch in there and see if it works. If not, well the fan switch is a good idea anyways.

 

Some people say it doesn't matter about the charge, some say it does. At this point, I think it does. When I charge mine up, I'll see if it makes any difference on mine. I'm waiting til it gets hot around here first.

That cooling fan diagnosis in your sig line should help alot of people. I have the 88 camaro service manual which is almost identical. That thing should be a sticky around here with all the cooling fan issues I see

 

At one point a few people suggested that my sig line be a sticky. But it never happened.

As for the secondary fan. It makes sense that a proper charged system would turn it on while an undercharged one wouldn't turn the fan on. When the A/C is charged up, you get better performance. Less short cycling. More cold air to the cabin means more hot air to the condenser. More heat = higher high side pressure. Thus the high side pressure turns the secondary fan on.

Let's say the system has 1.0 lb of refrigerant in there. Less than half the recommended full charge. It's going to short cycle and the best your duct temps will get to is around 55° (guessing on that). That's not going to send very much heat to the condenser. The system simply doesn't shed enough heat to generate raised high side pressures. Fan stays off. Simply not needed to keep the high side pressure in check.

 

That's my belief as well

 

I charged my A/C today. The secondary fan came on after I put 1 can in. So it definitely matters.