Strange ECC behaviour

**stevedee3** · 23rd May 2006, 01:25

Hi everyone,

I posted this ages ago on Vectra-Sport, before I realised all the C owners were here... Well it's getting cold in the mornings again and this problem is annoying me again.

Has anyone noticed this (or do I have a problem)?

If I turn the car on, then immediately press both front and rear demist buttons (on the climate control unit), the rear demister turns off after a couple of seconds. It seems to be that as the fan builds up speed, the demister cuts out.

**Gsi3.2** · 23rd May 2006, 06:51

I wonder if it's a current draw protection thing?? The rear window demist will pull about 30 amps and the blower motor on full chat in a sealed car will pull at least that..I wonder if VX designed it that you couldn't run both at the same time..

I'm off for a play..

**Gsi3.2** · 23rd May 2006, 07:02

That shot me down in flames..

The ECC in mine just let both run for 5 mins till the rear screen was clear..All the car did was pick the rev's up slightly as the electrical load was applied..

In the pre-canbus day's i'd have said the relay was at fault, but are they still fitted??

**Ozz** · 23rd May 2006, 07:48

Hmmmm, I had both the front & rear demisting away on Saturday evening & had no probs.

**Duncan** · 23rd May 2006, 11:20

Originally Posted by stevedee3

I posted this ages ago on Vectra-Sport, before I realised all the C owners were here...

Originally Posted by stevedee3

If I turn the car on, then immediately press both front and rear demist buttons (on the climate control unit), the rear demister turns off after a couple of seconds. It seems to be that as the fan builds up speed, the demister cuts out.

I've had something similar, but not specifically in conjunction with the front demisters.

I'll start up the car on the drive, turn on the heated rear window/mirrors and by the time I've got off the drive I've noticed that they've turned off. I turn it on again and it then stays on. Doesn't do it every time, but often enough to have noticed it.

I've no idea what it may be, but as it's a small 'niggle', I've never bothered too much about it.

D

**stevedee3** · 23rd May 2006, 11:47

OK, here's my submission for world's longest post...

Originally Posted by Ozz

Hmmmm, I had both the front & rear demisting away on Saturday evening & had no probs.

Originally Posted by Gsi3.2

The ECC in mine just let both run for 5 mins till the rear screen was clear..

When the "weird behaviour" happens, the rear demister will turn off almost as soon as it was turned on. It's stays on just long enough for you to look away... I'm not talking about the 15-20 minute timer. It only seems to happen when the car has just been turned on.

Originally Posted by Gsi3.2

I wonder if it's a current draw protection thing?? The rear window demist will pull about 30 amps and the blower motor on full chat in a sealed car will pull at least that..

I think you may be on the right track, Gsi3.2. I imagine the way to make the ventiliation fan draw the most current is to have it static and then ask it to go at maximum speed. Similarly a cold demister probably draws a large current. Maybe doing both at once causes such a large current draw that the ECC unit has to switch something off?

Originally Posted by Duncan

I'll start up the car on the drive, turn on the heated rear window/mirrors and by the time I've got off the drive I've noticed that they've turned off. I turn it on again and it then stays on. Doesn't do it every time, but often enough to have noticed it.

That sounds like what I'm talking about. I find myself later wondering why the window and mirrors haven't demisted.

It took me a while to work out what was going on. I thought I just hadn't pushed the rear demist button properly until I took a closer look.

So, to recap (and just to make this post even longer

), the procedure is:

Cold (cool?) car (been off for at least ~10 minutes)
Turn ignition on
Immediately turn on front and rear demisters. Don't take your eyes off the indicator LEDs
If the "weird behaviour" occurs, the rear demister will turn off within a second or two.

The following things don't seem to make any difference:

Whether the air conditioning commpressor is on or off ("Economy" mode)
Whether the headlights are on or off
Whether the seat heaters are on or off

**Duncan** · 23rd May 2006, 11:55

Originally Posted by stevedee3

That sounds like what I'm talking about. I find myself later wondering why the window and mirrors haven't demisted.

Yep, I don't always notice it straight away. Often 10 mins into my journey when I notice the mirrors haven't started to clear.

I rarely use the front demister feature (only in cold winter really) so it's not that that causes it. I haven't done any other 'tests' to see if it only does it when certain things are turned on as it's never been a big deal to me - I just push the button again! lol

It just seems to be if you turn on the rear window/mirrors straight after you start the car. If I don't do anything, then turn it on once I'm on my way then it stays on.

**Big Bri** · 23rd May 2006, 18:08

So its not just mine that this happens to?

In the cold weather I would lean in and start the car and turn on first the windscreen defrost. Then turn on the rear screen/door mirrors before attacking the ice on the windscreen. I noticed that when scraping the side windows the rear demister light had gone out. Press it again and it stays on.

I watched this on other days and it always turns off after a few seconds. It always stays on when pressed a second time.

I haven't a clue why it does this.