Cause and solution please

I did another thread and didn't really get help to a problem I have:
I asked for help concerning the GEN/alternator light coming on.
I narrowed the problem down to my electric fan I installed. I firstly had it running on a radiator fan switch but this was running way to long and could not find a temp range which suited the open/closed range of the OBD11. it kept on running the sysytem to cold. I then hooked the fan via a relay to the aux fan wiring. since i have done this the GEN light has been coming. I tested it today and found this to be the culprit.

I have heard that the main fan uses a negative to switch the fan on as it has a permanent positive. how would i run this via a relay. this way seems to work better as my xj seems to run a little warm here in South Africa where temps average 35-38 *C and the fan coming on for short periods seems to work better than it staying on for a long period where it cools the complete system down to almost cold.

Has somebody got a diagram that I may use:dunno::dunno:
Steve

It's the thermostats job to keep a fairly constant temperature in the motor, not the fan. Don't trust the in dash gage, if the sensor is malfunctioning, it may be lying to you. Messing with the electric fan circuit in a later model XJ, you may have crossing up the temperature sensor circuit.
What year XJ?
I'm fairly adept at automotive electric. I'd be hesitant to pump any possible plus voltage through the ground circuit in my PCM used to control a relay (designed for a very small amount of current).
I'd be double hesitant if I didn't have schematic or enough electrical knowhow to wire a relay into a ground circuit.
To put it bluntly, I'd stop messing around, put it back the way it was before I had to buy a new computer. I've seen computers fry, just by reversing polarity on the wrong circuit.

8Mud said:

It's the thermostats job to keep a fairly constant temperature in the motor, not the fan. Don't trust the in dash gage, if the sensor is malfunctioning, it may be lying to you. Messing with the electric fan circuit in a later model XJ, you may have crossing up the temperature sensor circuit.
What year XJ?
I'm fairly adept at automotive electric. I'd be hesitant to pump any possible plus voltage through the ground circuit in my PCM used to control a relay (designed for a very small amount of current).
I'd be double hesitant if I didn't have schematic or enough electrical knowhow to wire a relay into a ground circuit.
To put it bluntly, I'd stop messing around, put it back the way it was before I had to buy a new computer. I've seen computers fry, just by reversing polarity on the wrong circuit.

Click to expand...

I hear what you are saying. I s there not a way to wire this type of circuit up. i am only using the ground to switch the relay. If not mistaken the the aux fan runs permanent + and a switching -. is the draw to much for the PCM? will it not help to put a diode inline so the PCM doesn't see the draw. why i'm asking is cause this is what a friend told me to try.

stevieb said:

I hear what you are saying. I s there not a way to wire this type of circuit up. i am only using the ground to switch the relay. If not mistaken the the aux fan runs permanent + and a switching -. is the draw to much for the PCM? will it not help to put a diode inline so the PCM doesn't see the draw. why i'm asking is cause this is what a friend told me to try.

Click to expand...

If I understand correctly you have two electric fans? And want to wire the primary fan into the aux fan control circuit.
The primary fan should run anytime the motor is running *but* isn't really needed at higher speeds.
My advice is to *not* wire the primary fan into the aux fan control circuit.
I'd use a low tech solution and buy a simple adjustable thermostat, put the feeler/sensor in the air flow (engine side of the radiator) and adjust it to switch at around 140-160 deg F. or ( 60-70 C. +/-). The reason I say adjustable is it may take some fine tuning. But if your sure of what temperature you want it to switch, a "Bi-metal/ snap switch" could be mounted to the inside of the radiator fairly easy (cable tie ?).

http://www.tod.com/searchProducts.asp?PageID=10&TechnologyID=1
http://sensors-transducers.globalspec.com/Industrial-Directory/switch_thermal_klixon

You can find Klixon (bi-metal/snap switches) fairly easy, finding exactly what you want in a catalog my take some time (I'm not going to do your homework for you ). Water resistant 70 C. closed and 60 C. open will likely work out for you. Use the Kixon to switch a relay, or buy one with enough amperage to switch the fan directly.
Problem solved and your generator light should go out, unless the fan draws so many amps the alternator can't keep up.
Many dual speed fans use a heat generating resistor for the low speed and can actually use more amps at low speed than high speed.
What your friend said about a diode to segregate two parallel relay (switches) on a single circuit is always a good idea. You can actually buy the relay with the diode already inside (incorporated).

stevieb said:

I did another thread and didn't really get help to a problem I have:
I asked for help concerning the GEN/alternator light coming on.
I narrowed the problem down to my electric fan I installed. I firstly had it running on a radiator fan switch but this was running way to long and could not find a temp range which suited the open/closed range of the OBD11. it kept on running the sysytem to cold. I then hooked the fan via a relay to the aux fan wiring. since i have done this the GEN light has been coming. I tested it today and found this to be the culprit.

I have heard that the main fan uses a negative to switch the fan on as it has a permanent positive. how would i run this via a relay. this way seems to work better as my xj seems to run a little warm here in South Africa where temps average 35-38 *C and the fan coming on for short periods seems to work better than it staying on for a long period where it cools the complete system down to almost cold.

Has somebody got a diagram that I may use:dunno::dunno:
Steve

Click to expand...

I don't know if what we have is identical to a South African XJ as we don't have GEN lights. Our main fan is mechanical, not electrical.

Our Aux fan is Electrical and one side of the connector on the fan is grounded. The other lead goes to the contact side of the relay, then to +. The control side of the relay is controled by either the PCM which completes the ground, or a hard temerature switch to +.

If you want to control another relay from the aux fan, I would put the control side (coil) across the leads to the aux fan and use the switched output of that relay to switch your fan on and off. The second fan will turn on and off with the AUX fan.

If you want to get fancy with the control side, you can do a fan override by installing a set of diodes cathode to cathode. The jct of the cathodes goes to the relay. On anode goes to your aux fan +, the other to a switch to +. A 1N4006 should would fine (2A, 600PIV) for the logic in this situation. The second fan will turn on and off with the AUX fan OR turn on with the overide switch.

Ron

Zuki-Ron said:

I don't know if what we have is identical to a South African XJ as we don't have GEN lights. Our main fan is mechanical, not electrical.

Our Aux fan is Electrical and one side of the connector on the fan is grounded. The other lead goes to the contact side of the relay, then to +. The control side of the relay is controled by either the PCM which completes the ground, or a hard temerature switch to +.

If you want to control another relay from the aux fan, I would put the control side (coil) across the leads to the aux fan and use the switched output of that relay to switch your fan on and off. The second fan will turn on and off with the AUX fan.

If you want to get fancy with the control side, you can do a fan override by installing a set of diodes cathode to cathode. The jct of the cathodes goes to the relay. On anode goes to your aux fan +, the other to a switch to +. A 1N4006 should would fine (2A, 600PIV) for the logic in this situation. The second fan will turn on and off with the AUX fan OR turn on with the overide switch.

Ron

Click to expand...

the GEN light is basically the alternator/battery light on the instrument panel, the light that comes on if the alternator goes bad. not sure what you guys call it over there.

anyway this light will stay off till the fans kick in and then the light comes on and stays on.
the way i have it hooked up is i have a relay (3 point heavy duty) connected up to the positive wire (green) going to the aux fan, oh forgot i removed my mech fan and replaced with a 12v fan from a BMW. it is a 16" jobby. the relay kicks in once the ignition comes on cause the aux fan has a permanent + and switching - (black) as you well know.
where do you think this problem could be coming from? i am not to bright with car wires but get around the things when needed.
you could not perhaps draw a quick diagram for me as this is starting to scare me and don't want to blow the PCM.
you can e-mail me at [email protected]
for the mean time i will run it as in the past, from a radiator switch or maybe just switched straight to 12v.
thx so far
steve
ps. the second circuit you mentioned sounds quite interesting:worship:

Generator/Alternator are supposed to be one in the same. Damn GM Engineers and others following!

I'm wondering why the generator light is coming on. Maybe you are introducing voltage where there shouldn't be any. Into the wrong circuit or wiring in a ground path, that shouldn't be there.
Your fan may be drawing too many amps, too many amps from your power source (or from whichever circuit you wired into for the primary fan, + plus).
Why would you want to do it in the first place? Switch your primary fan on, using the aux fan circuit. The aux fan circuit is designed to turn the aux on when your engine is above normal operating temperature. Above normal operating temperature IMO seems like a poor choice as a starting point for the cooling system in an XJ (any XJ). Summer is on the way in your hemisphere.
It's just been my experience that adding stuff to the existing harness and sub systems can have unexpected consequences (you may get away with until you don't). Some (much) of the electrical in the XJ is marginal at best.
I tend to start at the battery, wire an inline fuse near the battery and start from there. Segregate my add ons from the existing harness. Install my own fuses and wiring. It makes it much easier to troubleshoot, really doesn't cost anymore and is unlikely to generate conflicts with the existing sub systems or melt any wires, cause any conflicts or burn up any expensive components in the existing system.
If your motor is under cooling, the problem is likely to be something else other than the fan. If you are driving much above 60 KPH, you are likely pushing more air through the radiator than the fan every could.
The BMW fans out of the models with A/C move some serious air. Most are two speed, did you hook the right wires up? It could be easy to wire in a loop through the resister and draw some serious amperage without completely burning the harness up (maybe). I'm to lazy to go out to the garage and check (dig through my junk) but if I remember correctly BMW favored green as ground and black (red or some other color) as plus voltage. Many of the BMW fans I've seen push, they don't pull. Running them in reverse doesn't reverse the airflow.

Hi 8MUD
When i got the xj it had no thermo in, i went offroading and she would get hot. i then started to investigate and found there was not thermo, pump was shot and the upper pipe was incorrect. It also did not have an aux fan. I got an after market jobby.
I replaced the pump, piping, installed a genuine thermostat, flushed the system and had the radiator cleaned out. the visco clutch fan was also shot, it never kicked in as it should have. Well to tell you the truth it all helped zip as she still tends to run up to temps where the aux comes on easily. this i think is due to no fan running cause if it had the clutch fan there would be a constant flow of air.
I then installed a 16" BMW fan which to be honest draws a crap load of air and cools her down very quickly. i have this running on a radiator switch which comes on at 102*C and off at 91*C. i could not get anything higher on the off side and nothing lower on the on side. the consumption shot up to and was getting 4.5 km/l where before i was getting 8 km/l. i could only explain this to open and closed loop being interfered with on the low side where the system would then think the coolant was cold.

OK back to the GEN/ALT light (my xj originates from Brazil i.e. GEN light). I think or know I found the problem tonight. I was thinking like a dumb ass when i connected it up the other night. it was a rush job. anyway i found that the fans earth was not connected up to the aux neg wire but to the body, i changed it and connected it to the aux neg wire (black) and the signal wire to the aux pos wire (green). problem has disappeared and it seems to cycle well. the only problem now is that it (while idling) cycles quite often as there is not air movement unless the fans are running. i wish there was a way to convert the fan to a dual speed or at least get it to run at a lower speed and have it constatly running as the clutch fan would have.

Any thought 8MUD???
thx so far
steve