BHI ECU diagnostics?

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pseud
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Joined: 21 Jan 2012, 22:10
Location: Leeds, UK
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BHI ECU diagnostics?

Post by pseud »

Hi folks

I'll get the hang of these forums - new subject = new topic... (1st posted at the end of an old topic.)

I have been attempting to perform some diagnostics to try and get to the bottom of what's going on. I had assumed that the motor would appear stuffed when I took it off, but it looks ok. No signs of water or other crud, a fair bit of black fluff/dust from the bushes, but that's to be expected?

So, I've put the ecu back in the car to perform some diagnostics on the control wire (smaller of the 3 going to the motor power transistor). I haven't been able to find any perameters for what this is supposed to show - other than some mention of 10-12v when a door is opened. Mine doesn't. It shows:
* 0v when still
* 0.75v for a few seconds when the key fob is unlocked, then back to 0v
* 0.75v for a few seconds when the door is opened, then back to 0v
* 0.75v for a few seconds when the door is closed, then back to 0v
* 12.5v when the ignition is turned on, dropping away during starting and then returning to about 12.5v constantly when the engine is running (I didn't run the engine for more than 5 mins)
* 12.5v continuing while the engine is turned back off for a few minutes, then
* 0.75v for a minute or so, then
* 12.5v for a couple of minutes, then
* 0v while still again

I may have opened the door and shut it while the engine was running and there may have been a rise to over 13v for those moments, or my memory might be playing tricks with me...

Is this normal behaviour (not mine, the cars)? What is normal?

What should the resistance be on the armature windings?

And, finally - how would those readings explain the fuse blowing: 2nd 3 weeks from the 1st, 3rd a couple of days from the 2nd and 4th a couple of minutes after the 3rd...

Any musings welcome...

Thanks,
Morgan.
L15 (my first car and first profit: bought for $750 aged 16; sold for $1,500 aged 20)
Xantia Mk1 SX 1.8 (gone) (aged 40, oh dear where did they go...)
Xantia Mk1 SX 2.0 (gone)
Xantia Mk1 SX station wagon 2.0 (gone)
C5 Mk1 Ex (dead, and going... gone!)
Xantia Mk2 Ex (going)
cachaciero
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Joined: 13 Apr 2009, 07:24
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Re: BHI ECU diagnostics?

Post by cachaciero »

Opening or closing the doors should not trigger a "pump run" signal so 0.75v seen when opening / closing doors is probably just transient noise.
The pump should only run if either the rear or front suspension is not to commanded height. Without the aid of a Lexia which allows you to drive the motor independently the best way is to select low suspension and having sunk to lowest height then select max high this should give you a few seconds of motor run time.

I don't know what the armature resistance should be but it will be low, probably less than 1 ohm, anyway measurement even with equipment that could measure very acurately low resistances would not be likely to identify shorted turns. It does seem to me the most likely problem is the armature I would suggest that you closely examine the armature and look for overheated segments indicated by colour usually a blue tinge to the normal copper colour if not outright burnt and melted copper. Another check you could do is to do a resistance check from each armature segment to the armature iron any continuity indicates a short to ground, however if this check is clean it doesn't mean that there are no inter winding shorts.

cachaciero
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1995 XM 2.1 TD Auto SX died @ 140K
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