1988smithy said:
Yeah 3 wires, one of them is lickle so guessing command wire

I think I'll try a test lamp tomorrow on the harness plug, so test lamp probe in command wire pin but do I earth to negative or positive?

Teat lamp on positive pin and earth to negative will tell me if I've got constant 12v feed wont it, then as above to test command wire with ignition and a/c on

Then as you said to test the socket on the fan?
Click to expand...
JLR do love to complicate things. The signal on the command wire is unlikely to be a simple ON/OFF, more likely to be a pulsed or graduated signal that controls the speed of the fan.
You can check the constant 12 volts and ground at the supply connector with a test lamp, personally I would not go near the command wire with a test lamp, that is a job for a DVM or a scope. With the aircon on, you should see a change of level on the command wire, it may be as little as 1 or 2 volts. without the drawings I cannot know exactly what the signal will be.
Getting the fan to run will not be simple. Applying the constant 12 volts and ground will not make it run as that will require the command signal.
Have you actually checked that the fan is not seized?
 
Datatek said:
JLR do love to complicate things. The signal on the command wire is unlikely to be a simple ON/OFF, more likely to be a pulsed or graduated signal that controls the speed of the fan.
You can check the constant 12 volts and ground at the supply connector with a test lamp, personally I would not go near the command wire with a test lamp, that is a job for a DVM or a scope. With the aircon on, you should see a change of level on the command wire, it may be as little as 1 or 2 volts. without the drawings I cannot know exactly what the signal will be.
Getting the fan to run will not be simple. Applying the constant 12 volts and ground will not make it run as that will require the command signal.
Have you actually checked that the fan is not seized?
Click to expand...
Ive got constant 12v supply according to multimeter, I'll test for voltage increase with a/c on.

This is beyond me tbh, might get an auto spark to test for me.

Fan spins freely mate
 
1988smithy said:
Yeah 3 wires, one of them is lickle so guessing command wire

I think I'll try a test lamp tomorrow on the harness plug, so test lamp probe in command wire pin but do I earth to negative or positive?

Teat lamp on positive pin and earth to negative will tell me if I've got constant 12v feed wont it, then as above to test command wire with ignition and a/c on

Then as you said to test the socket on the fan?
Click to expand...

When you look at 1 of the previous attactments you will see, 1 wire is permanent live, 1 is permanent earth.
the third controls the amount of volts that goes through to control the speed. So must be some trickery inside the fan.
I wouldn’t put a voltage near that, as in the other stuff it says a ”signal“ is sent?? What is the signal?

But points 1 & 2 should be easy to check.

J

i will confess I found the files but didn’t read them till now :)
 
1988smithy said:
Ive got constant 12v supply according to multimeter, I'll test for voltage increase with a/c on.

This is beyond me tbh, might get an auto spark to test for me.

Fan spins freely mate
Click to expand...
A constant 12 volts on the command line? In that case it may reduce to increase fan speed.
 
1988smithy said:
Will update tomorrow, its absolutely pìssing it down here 😤
Click to expand...
I have just thought, the system may need to see a load on the +12 & ground lines, so put your test lamp on those lines, turn the aircon on and you may need to start the engine, then put your DVM between the command line and ground, you could also check with the DVM between the command line and +12.
 
Datatek said:
I have just thought, the system may need to see a load on the +12 & ground lines, so put your test lamp on those lines, turn the aircon on and you may need to start the engine, then put your DVM between the command line and ground, you could also check with the DVM between the command line and +12.
Click to expand...
Don't forget the fan won't always run. Once the system has good pressure and has absorbed enough heat the fans won't necessarily run straight away. 🤔
 
Datatek said:
I have just thought, the system may need to see a load on the +12 & ground lines, so put your test lamp on those lines, turn the aircon on and you may need to start the engine, then put your DVM between the command line and ground, you could also check with the DVM between the command line and +12.
Click to expand...

Just tried this mate, I'm not getting anything from the command wire on DVM on +12 or ground

Also had just test light on +12/ground and command line, nothing

Am I looking at break in the wiring then?

Sorry for delay in updating this, weather and life got in the way a bit
 
1988smithy said:
Just tried this mate, I'm not getting anything from the command wire on DVM on +12 or ground

Also had just test light on +12/ground and command line, nothing

Am I looking at break in the wiring then?

Sorry for delay in updating this, weather and life got in the way a bit
Click to expand...
More likely that the control module is at fault or there is a corroded connector than an actual break in the wiring but you never know.
 
1988smithy said:
Test light on command wire (engine running a/c on) and tried positive and negative ground - no light
Click to expand...

need to look back but if you don’t have a light on the 12v and ground, I would start there, I was sure the wiring dia show permanent live and ground?
need to look again.

J
 
marjon said:
need to look back but if you don’t have a light on the 12v and ground, I would start there, I was sure the wiring dia show permanent live and ground?
need to look again.

J
Click to expand...
He does have a light between permanent +12 & Ground, it's the command line that is dead.
 
Datatek said:
He does have a light between permanent +12 & Ground, it's the command line that is dead.
Click to expand...
Ok well I missed that.

But knowing LR the signal could be anything.
Square wave or PWM type stuff so a DVM won’t see it. (I have no idea what they are :vb-confused2: ). But sounds in the oscilloscope stuff.

Need to Read the docs again it explained conditions needed to kick in fan.

J
 
Could it be the coolant temp sensor?
marjon said:
Ok well I missed that.

But knowing LR the signal could be anything.
Square wave or PWM type stuff so a DVM won’t see it. (I have no idea what they are :vb-confused2: ). But sounds in the oscilloscope stuff.

Need to Read the docs again it explained conditions needed to kick in fan.

J
Click to expand...
Think your docs are for td6 mate, I was really struggling to find tdv8 era electronic worksheets, but came across these if its any help
Screenshot_20230807-155153_Chrome.jpg
Screenshot_20230807-155157_Chrome.jpg
Screenshot_20230807-155202_Chrome.jpg
 
You must log in or register to reply here.