Defender Source Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
446 Posts
Discussion Starter #1
Has anyone that's installed an aftermarket heated windscreen ever incorporated the ECM's pre-programmed ability to adjust the engine idle speed? By my math, I'd run a purple/yellow wire from pin 8 on the ECM to the trigger side 86 or 85 of the windscreen relay or the output side of a timer. First, any issues with my math? Second, is this even needed?

446779
Screen Shot 2020-05-22 at 1.48.39 PM.png
Screen Shot 2020-05-22 at 1.49.24 PM.png
 

·
Premium Member
Joined
·
4,663 Posts
im assuming this is just to create a high idle situation so the engine warms up faster or that the current draw isnt more than the charging system is putting out at idle?

if its the latter a smaller pulley on the alt would do the same thing ...all the time with no need for wiring.
 

·
Registered
Joined
·
446 Posts
Discussion Starter #3
Correct, increase idle to support the increased load demand. That said, I don’t know what the ECM is pre-programmed to do.
I’m actually almost complete with a full loom overhaul on the ECM so, it’s no additional work. I’ll post finished pics when done.
 

·
Premium Member
Joined
·
1,263 Posts
idle does not change, it remains stable. in order to keep battery from draining the relay will not allow electrical load below a threshold unless engine is running.
on range rovers of the same vintage there is a relay aptly named "load relay" which acts as a gateway to the "timer" relay.
the 'timer" relay circled in your diagram is exactly what the name implies a pre-determined circuit "run" time. I don't have specs in-front of me but from memory, I believe the heater circuit stays on between 3 and 5 minutes only and it draws a high amount of amperage.
here is a bit of info, Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting
 

·
Registered
Joined
·
446 Posts
Discussion Starter #5
That’s not entirely accurate. Per the screenshot (second picture) of the “13/14CU and 14CUX Systems” document from LR, the ECM is preprogrammed to adjust the idle speed to handle the additional load. It’s not a question of will it work, it’s a question of where to tie the purple/yellow wire. Frankly, the way I see it, it can be tied-in exactly as I’ve noted above or I can also tie into the positive side (purple/slate) of the Windshield terminals. The ECM simply needs the positive indication that there’s an active load.
 

·
Registered
Joined
·
446 Posts
Discussion Starter #7
Have not delved into this on a defender but have a 94 lwb with 14cux and when I turn on the heated screen/mirrors idle does not bump up.
.

Doug, is your heated windscreen stock or aftermarket? Sounds aftermarket if there are mirrors too? The easiest way to tell is to look to see if your ECM loom has a pin at the # 8 position.
 

·
Premium Member
Joined
·
13,599 Posts
Stock.
Range Rover classic County's came stock with heated screen, mirrors, washer jets, etc. They used the same injection system as the defender sold here in the US. I have retrofit the RRC fuel injection systems and range rover 3.9 and 4.2 engines in a bunch of early diesel or carbed 4 cyl defenders. Now that I think about it there are a pair of wires that plug into the loom just before it passes through the bulkhead grommet (ie under the dash) on a classic. I've never gone back to look @ RAVE to see what they were for as they didnt effect the install or engine operation in a defender.
My range rover is all original except for the air suspension and exhaust.
 

·
Registered
Joined
·
49 Posts
idle isn’t affected any more than moving all the windows at once or something like that, it’s just a fairly big draw on the alt. on the classic the oil pressure switch needs to be active to turn on the heated screen
 

·
Registered
Joined
·
446 Posts
Discussion Starter #10
Stock.
Range Rover classic County's came stock with heated screen, mirrors, washer jets, etc. They used the same injection system as the defender sold here in the US.
Sorry, missed the RRC part. Again, the easiest way to check is to look at the loom connector at the ECM. If the loom has a pin at #8 then, it should raise the idle.

Now, do I think it’s a need to have or a nice to have? I think the latter as long as the windscreen has a timer.
 

·
Premium Member
Joined
·
13,599 Posts
I'm going to back up on what I said before about not noticing an idle bump up. Thinking back ,ea of the times I have used the heated screen,the truck was already in high idle warm up mode triggered by ambient air temp, fuel temp, coolant temp sensors (who knows which, or was it all ?) and I was just engaging the screen to melt snow or ice off so we could get going.
The heated screen's are pretty pretty quick to clear a crusted over windshield.
Classics also have a thermostatic control valve on the trans fluid, the system reroutes fluid from the cooler and instead runs it through the radiator tank to heat the trans fluid so you get smoother shifts quickly on cold mornings. Once up to temp, fluid is rerouted to the cooler.

User Name arent you located in the deep South ?
 
1 - 13 of 13 Posts
Top