Cutting out when hot - Advice on where to go next
Discussion
There's plenty of posts similar to the following here at PH, posting in-case you've not read any
The coil supply voltage can only be measured correctly by having the coil load on/in the circuit
A bad supply or a supply through a ballast resistor will still measure as 12 volt when the coil load isn't on/in the circuit
You need to remove all cables from the ignition coil negative terminal
Use a jump lead to connect the coil negative to battery negative or a known good earth
Now switch the ignition on and measure the voltage at the coil positive
Don't leave the ignition on for too long as the coil could overheat, 10 to 15 seconds isn't a problem
You will have then measured the supply voltage to the coil while it is under coil load (coil is drawing current)
The coil supply voltage can only be measured correctly by having the coil load on/in the circuit
A bad supply or a supply through a ballast resistor will still measure as 12 volt when the coil load isn't on/in the circuit
You need to remove all cables from the ignition coil negative terminal
Use a jump lead to connect the coil negative to battery negative or a known good earth
Now switch the ignition on and measure the voltage at the coil positive
Don't leave the ignition on for too long as the coil could overheat, 10 to 15 seconds isn't a problem
You will have then measured the supply voltage to the coil while it is under coil load (coil is drawing current)
Penelope Stopit said:
There's plenty of posts similar to the following here at PH, posting in-case you've not read any
The coil supply voltage can only be measured correctly by having the coil load on/in the circuit
A bad supply or a supply through a ballast resistor will still measure as 12 volt when the coil load isn't on/in the circuit
If the supply side voltage isn't dipping then the supply circuit isn't causing the problem and there is no point testing that further.The coil supply voltage can only be measured correctly by having the coil load on/in the circuit
A bad supply or a supply through a ballast resistor will still measure as 12 volt when the coil load isn't on/in the circuit
If the ignition system is not loading the coil then that explains the problem and is where you need to investigate.
gizzardio said:
dropping down to about 9V during the time when it was turning over which I guess is just down to the load being pulled during turnover on starter motor etc
As low as 9 volt is also a problem but doesn't mean it's causing the problemFully charged battery shouldn't drop below 9.6 volts when cranking and the coil supply with coil load in the circuit should be fractions of a volt less than the battery voltage when cranking
Worth testing all the above mentioned voltages before throwing parts at it
OK I'm going to do the measurements as suggested.
Only thing I'm confused about though is when the car is functioning properly when cold, if I measure the coil with -ve disconnected and linked back to battery or good earth, this could show that all is well in terms of the supply. Which it probably would. So I would need to wait until the car has stopped running when warm (when something is breaking down electrically) and then rig up this arrangement?
Only thing I'm confused about though is when the car is functioning properly when cold, if I measure the coil with -ve disconnected and linked back to battery or good earth, this could show that all is well in terms of the supply. Which it probably would. So I would need to wait until the car has stopped running when warm (when something is breaking down electrically) and then rig up this arrangement?
gizzardio said:
I would need to wait until the car has stopped running when warm (when something is breaking down electrically) and then rig up this arrangement?
You would, if you want to rule that possibility out. Heat related ignition problems are IME always a breakdown of the low voltage electronics or the coil. It's remotely possible that it is a heat related wiring fault on the LT supply side, but I've never seen that happen and it doesn't seem at all likely compared to the other potential causes.gizzardio said:
OK I'm going to do the measurements as suggested.
Only thing I'm confused about though is when the car is functioning properly when cold, if I measure the coil with -ve disconnected and linked back to battery or good earth, this could show that all is well in terms of the supply. Which it probably would. So I would need to wait until the car has stopped running when warm (when something is breaking down electrically) and then rig up this arrangement?
Carry out the test when all is working properly and take note of the readingsOnly thing I'm confused about though is when the car is functioning properly when cold, if I measure the coil with -ve disconnected and linked back to battery or good earth, this could show that all is well in terms of the supply. Which it probably would. So I would need to wait until the car has stopped running when warm (when something is breaking down electrically) and then rig up this arrangement?
Carry out the same test when the fault appears
This way a comparison can be made
A little update here. So I've tested everything as advised as Stopit recommended and it came back in normal range in those conditions. I also have been reading this section from the Range Rover Classic manual.
I have followed these steps too and apart from one check which I can't understand how it could be correct in the manual, all checks lead to amplifier module. I bought new and replaced and I ran it for half hour without cutting out. Previously it cut after 5-10mins. I'm going to take it for a drive to test it out more but that's where I'm up to now.![](https://thumbsnap.com/t/FxHh6H6L.jpg[/img]</a> <a href="https://thumbsnap.com/Qz4c3E5S" Target="_blank" rel="nofollow">[img]https://thumbsnap.com/sc/Qz4c3E5S.jpg)
I have followed these steps too and apart from one check which I can't understand how it could be correct in the manual, all checks lead to amplifier module. I bought new and replaced and I ran it for half hour without cutting out. Previously it cut after 5-10mins. I'm going to take it for a drive to test it out more but that's where I'm up to now.
Yep that has to be what's happening on that test.
One more thing, I bought my amp module from Race tech and the guy said I should buy the 3 pin one even though mines a 2 pin originally cos he's had so many 2 pin versions fail due to poor quality. The 3 pin ones they sell are decent apparently.
I had to cut the 2wires and create new connector plug. You just don't use the centre pin. I think that must be an earth for when the module is mounted remote from dizzy as it earths through the mounting plate screw on the dizzy in my case
One more thing, I bought my amp module from Race tech and the guy said I should buy the 3 pin one even though mines a 2 pin originally cos he's had so many 2 pin versions fail due to poor quality. The 3 pin ones they sell are decent apparently.
I had to cut the 2wires and create new connector plug. You just don't use the centre pin. I think that must be an earth for when the module is mounted remote from dizzy as it earths through the mounting plate screw on the dizzy in my case
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