Back story... the hs worked great up until the last couple of frosts earlier this year but then stopped. Decided to investigate this the other day. Both relays clicked so off with the plenum (much quicker to say then do!) And a poke with a dmm showed healthy voltage at both white connectors (disconnected) using both the battery and the ground stud for the hs. The ground stud looked a tad rusty though so I went to remove the nut and the stud sheared off. I'm hoping (bear with me here, I'm keen but green with leccy stuff!) that the stud was maybe causing high resistance and therefore the becm wasn't seeing the necessary load so it wouldn't work the hs. The ground stud is the only common connection under the plenum for both sides of the hs and as they both stopped working at the same time that sounds plausible to me.
That ground stud is now all repaired and finally to my question.
How can I test that the screen is now working? I have nano and a dmm and enthusiasm but that's it.
Googling about has led me to believe that a clamp meter may be useful?
Chris
As you probably realise, it will only power up the relays with the engine running so measuring current draw with your DMM is probably not a good idea. A clamp meter will show you if it is drawing current but it won't show you how much of it is working. When they fail they tend to lose strips so verifying if all the screen or only part of it are working will be difficult. You could check on the two power feeds to see if one side is drawing more than the other though which will give you a clue. I've got one of these https://www.amazon.co.uk/UT210E-Current-Meters-Capacitance-Tester/dp/B00O1Q2HOQ/ref=sr_1_2_sspa?th=1 that works very well at very low currents so good for checking battery drain problems and doubles as a DMM and NFC checker (for seeing if a wire has live mains on it without having to actually connect to it) too.
Thanks, I've ordered that item.
The screen had no non working elements, it was perfect , heating wise, then nowt out of the blue. So with that instrument I've ordered I just put the clamp part around the connected cable and I'll get an amp reading of say 20amps per side ,( guessing) if the screen is heating up? Luckily I've replaced all the chewed head rusty screws with nice stainless steel ones so getting at the connections only takes around 15mins instead of the two hours the first time I had to get in there.
You've got it. By default it comes up to show AC, so there is a button you press to toggle between AC and DC and a Zero button otherwise it will show current flow from the earth's magnetic field. Clamp the end around a cable and it shows the current flowing in that cable. You have to go around just one, if you try to use it around a two core cable so it has both power and return, it will show nothing as they cancel each other out. If both sides show the same, then they are both drawing the same current so both working as they should.
I also remember from my past woes with the heated screen, that if there is any sort of short or open circuit, the nano will highlight it in the faults, and most likely the dreaded book should pop up in the HeVAC display.
I had this for a long time and it was puzzling, until I found corrosion in the C0229 connector (the big one by the footwell), which was keeping one relay permanently engaged.
Just putting this out there...shoot me down if I'm talking cobblers!
Start the engine with door and bonnet open, let everything settle for say 5 minutes, put the clamp around the battery positive, note reading, then switch on the front screen, would that tell me the screen is then pulling a load? I'm guessing the alternator might screw that idea.
Just putting this out there...shoot me down if I'm talking cobblers!
Start the engine with door and bonnet open, let everything settle for say 5 minutes, put the clamp around the battery positive, note reading, then switch on the front screen, would that tell me the screen is then pulling a load? I'm guessing the alternator might screw that idea.
leolito wrote:
I also remember from my past woes with the heated screen, that if there is any sort of short or open circuit, the nano will highlight it in the faults, and most likely the dreaded book should pop up in the HeVAC display.
I had this for a long time and it was puzzling, until I found corrosion in the C0229 connector (the big one by the footwell), which was keeping one relay permanently engaged.
One of the first jobs I did when I got the car as a project was to cut out those blocks both sides.
Oops, messed up the quoting it seems.
My reply is the last 4 lines in the above post.
Just had the time to look at this. Clamp meter set to 100 amps dc after zeroing and I'm getting nothing on either side, tried on 20a and 2a too. Checked and still got healthy voltage at the hws connectors. New windscreen or the clamp meter is faulty, bit of lunch then I'll have a think of where else I can check the clamp dc function. Battery cable positive and interior light on/off maybe?
That would do it, or just put the clamp around the battery cable and look at what the car is drawing then. With bonnet and a door open, it should be just over 1 Amp. Close the door and wait 2 minutes for the BeCM to sleep and you'll see it drop down to around 0.25-0.4 Amps. With a clamp meter you have to connect it around just one cable, either the positive or negative. If around both it will see current flowing one way and the same amount flowing the other way so they will cancel out. Also bear in mind that the meter will always default to AC if you change range.
Think the meter is faulty, didn't get anything like your readings then I got over heated in the sun so abandoned the fiddling for now.
I tried the other features using the probes and they work just the dc amps is questionable, not tried ac amps though.
I don't cope well in the heat, brain stops working so it's best to leave it a few days I think.
Wonder if some cars won't turn the heated screen on if ambient temperature is high?
Is there no way to connect an Ammeter or just listen for alternator whine?
It will only kick in if the engine is running so connecting an ammeter isn't a good idea as it would need to be able to handle the current for the starter.
Yes I meant connect the ammeter to just the hw wiring not at the battery
Lpgc wrote:
Wonder if some cars won't turn the heated screen on if ambient temperature is high?
Is there no way to connect an Ammeter or just listen for alternator whine?
I did wonder about ambient temperature but I'm getting voltage on/off with the switch at 28 degrees.
Chrisp38 wrote:
Lpgc wrote:
Wonder if some cars won't turn the heated screen on if ambient temperature is high?
Is there no way to connect an Ammeter or just listen for alternator whine?
I did wonder about ambient temperature but I'm getting voltage on/off with the switch at 28 degrees.
Ahh yes of course
You could connect the ammeter in place each of the fuses in turn ? That way you don't see current for other systems.
F32 does half the screen, plus the relay for the other side. F30 supplies the other side.