Hi, New to me 1996 LT1 T/A. This thing was abandoned for a long time. It now runs, drives & stops. I can not get my radiator fans to come on.

I have tested all fuses & cleaned with contact cleaner, all good.
I have pulled MAF Sensor to put car in S.E.S. mode to force fans to come on.
I had 2 extra AC-Delco Relays & played russian roulette with them to no avail.

Ho do I jump the the relays to test the actual fan?????

Thanks.

 

Get an inline fuse holder with wire leads on it. Crimp some 1/4 inch male spade lugs to the ends of the wires. Install a 30 amp fuse in the fuse holder.

You insert the two male tabs into the relay socket where the 87 and 30 pins go in. That's the top and bottom pin in the middle column in this pic

Note that the fan relay might be a 4 pin unit, without the center pin.

 

Thank you.

 

Did you try to direct feed the fans to see if they even work? Unplug and run a + and -- with jumper wires.

 

I haven't used these, but they seem really handy for such a time as this. Saw them on a youtube channel called 'Car Wizard.'

 

Do your fans come on with the AC turned on? The temp sensor on the front of the water pump (Driver's side, upper half) is what the ECM uses for input to control fans functioning. I will try to post a link for trouble shooting and also a proper way to add a low/off/high switch.....many times, after doing all the tests, checks and replacing the above mentioned sensor....you will conclude that everything is as it should be and it is the actual computer that is faulty! This is very common!!!! I just went through this on my '96 Formula WS6, everything checked out, new sensor....fans come on with AC, but not automatically by engine temperature! I didn't want source a used computer just for this, so after doing some research, I found SLP used to make a fan controller switch and harness, but have discontinued it long ago....fortunately I was able to find one on ebay. There are other substitutes available! I will post links and pics to my post when I'm around my car! Just so you know, you just don't want to add a switch, there is a proper way to do this, which includes some resistors and proper wiring so that computer stays "happy" and is "tricked" into "thinking" everything is normal. I'll update ASAP, it is possible a new temp sensor will fix it, but also very probable that you'll need to add the switch👍

 

Four Seasons makes a thermostatic fan relay kit that might help you and not that expensive at maybe 35 bucks each. Their part number 35879.


These are adjustable for fan kick on temperature and you probably want one each of these per electric fan if your fans pull a lot of amps. And don't forget to connect the AC compressor line with this kit to turn a fan on immediately whenever your AC compressor is spinning - this lowers compressor head pressures and cools the cabin faster.

Rick

 

I haven't been able to get the fans to operate at all. I ordered some fused jumpers to eliminate the relays for elimination of that.

 

OK, when I jump Coolant 1 & Coolant 2 with a fused jumper, they work..................now what????? Thanks!

 

What exactly are your symptoms? Why do you think you have an issue with the fans?

Also, do you have the 2 fan relay system? Or the 3 fan relay system?

You can "activate" the fan relays by backprobing with a grounded wire on the dark green wire (fan 1) and on the dark blue wire (fan 2, and fan 3 if equipped). That should turn on the fans.

On the 3 relay system, I'm pretty sure the PCM controls all the relays. It's a series-parallel setup, with ground outputs from the PCM. One grounds only the coil on relay #1, which activates the fans in series. The second output grounds the coil on both relay 2 and relay 3, and activates the second fan and makes them parallel (both get full voltage and full current).

On the 2 relay system, one relay activates one fan, and the other relay activates the other fan. Some years, the second fan was activated by a coolant temp switch on the water pump on the LT1, and also by a pressure switch on the AC system (high side, condenser pressure). You can ground the wire at either sensor on those to activate the fan for testing. The temperature sensor has an "on" temperature of 238°F +/- if my (possibly faulty) memory is correct. I don't remember the pressure for the AC, but generally, the "condenser fan" cuts on around 250psi to 300psi on R134a systems.

Do you own an OBD-II scan tool or OBD-II dongle and android app? Can you check the ECT in the data stream from the PCM?

Two common issues that make the fans not cut on are 1) a faulty pressure cap. If the cap doesn't hold pressure, the coolant boils off at a temperature lower than the fan cut on temperature. A new cap will resolve this, generally for under $10. 2) a faulty (stuck open) thermostat. This will not allow the engine coolant temp to get high enough in "normal" driving to turn on the fans. It will also set a DTC and turn on the SES light.

 

Hi & thanks racer. I have replaced the thermostat & Rad cap with good quality OEM Spec'd ones, stock temp. I can run fine on open roads, on slow roads it climbs up, at long red lights it becomes scary, me wanting to pull over, I am not so far away from the red. It has not overheated yet. I tested it by what was suggested by turning the AC on & no fan. I also pulled the MAF sensor off to throw a SES which is suppose to activate the fans & nothing happened. I do not have a scan tool or an android. I have a I-phone 8 & I-pad 3. I am not opposed to spending some money.

 

Your symptoms do sound like fan issues.

Another thing I forgot to mention is, clean out in front of the AC Condenser, and especially between the AC Condenser and the radiator. That's another overlooked issue.

I don't know much about what's available on IOS for diagnostic apps.

I use Torque Pro on Android, and it does almost everything I need. I also have a few really good OBD-II bluetooth dongles, and a couple other apps that use them to do a few of the things than Torque Pro can't do. If you go that route, I highly recommend the OBD-Link MX+ for current cars, although it's a little over $100. If you'll be dealing mostly with 1996-2006 vehicles (before CANbus systems), the OBD-Link LX is adequate, and about half the price (I still have one of those and still use it). The under $30 "Chineseum clones" on Amazon and fleaBay can do a little bit of code reading and minor diagnostic work, but they are very slow and sometimes are buggy (cause the app to crash). They take forever to do some testing steps, and they are nearly useless for data logging if you're tracking multiple "PIDs" (a PID is a single data element, like "Engine Coolant Temperature," "Throttle Position," "Oxygen Sensor Voltage, Bank 1, Sensor 1" and there are literally hundreds of them you can track. The OBD-Link dongles can track 40 or 50 per second on 1996-1998 era PCMs, and up to 70 or 80 per second on more recent PCMs (with faster processors and faster data links). The cheap clones are lucky to hit 25 PIDs/second when logging data.

I haven't even looked if Torque Pro is available on IOS. It seems like I've heard it is not. But you could even get a cheap ($40 or so) Android "burner" phone (just don't activate it as a phone, it still works as a mini-tablet) or a decent 7"+ android tablet for your diagnostic app if you want to run the ones I use.

You can go into a good OBD-II diagnostic app and see what the actual engine coolant temperature that the PCM is getting from it's ECT sensor is. That's usually more accurate than the gauge, and often it will tell you what's going on. If that sensor is bad, then the PCM won't know the correct temperature and it might not turn the fans on at the correct time.

Oh, one last thing. You should also check for power to the relay coils. I can't remember if it's the 85 or the 86 terminal on the relay that gets power, but one of those should have +12V (or more) with the key turned on. If either relay isn't getting power to the relay coil, then the relay won't turn on when the PCM provides the ground for the coil. That's usually a different fuse and a different circuit than the fan power through the relay switch points (the 30-87 circuit).

 

Thanks racer. Please hang in with me, I will need a translator to understand what you are talking about. Please, I am totally serious. I will get what I need. thanks!