Cured my HA2 problem

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bernie
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Cured my HA2 problem

Post by bernie »

Simon I've finally cracked it[:)]
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mpr1956
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Post by mpr1956 »

I've been following this saga for a while, please let us all know how you fixed it !!
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Mandrake
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Post by Mandrake »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by bernie</i>

Simon I've finally cracked it[:)]
Image
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Tell us !!! [:D]
I'm planning to take my rear hydractive valve out completely on the weekend, not only to remove the damper valves to adjust the damping hole, but because I'm now almost sure that the valve is sometimes sticking in the hard mode for extended periods of time while driving when it shouldn't be...
Regards,
Simon
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Mandrake
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Post by Mandrake »

The suspense is killing me. [:D]
Regards,
Simon
bernie
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Post by bernie »

Right, listen up.
It's all to do with the HA2 solenoid operating.
As the initial voltage opens the valve there should be a modulated signal to keep it open.
As it happens that signal is there but the valve does close after the original voltage.
Apparently the diode in the circuit of the solenoid functions as a 'free wheeling diode' causing the current to turn, in the solenoid coil, on it's own impetus.
Are you following where this is going?
The bloody diodes buried in the solenoid casing are open circuit, so fit a couple of diodes in and [:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)]
I touched on this a while back.
I was trying to test the diodes across the coils but without success.
I got this info from a, french written, French site. Ooo laa laa
NiSk
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Post by NiSk »

Great Bernie, now draw us a diagram!
//NiSk
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Mandrake
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Post by Mandrake »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by bernie</i>

Right, listen up.
It's all to do with the HA2 solenoid operating.
As the initial voltage opens the valve there should be a modulated signal to keep it open.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Err, I hope that was a typo and you mean AFTER the initial voltage ? The initial voltage is just 12v DC, after which you get a pulse width modulated signal with a Peak to Peak voltage of 12v, and an RMS value of about 2.4v.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
As it happens that signal is there but the valve does close after the original voltage.
Apparently the diode in the circuit of the solenoid functions as a 'free wheeling diode' causing the current to turn, in the solenoid coil, on it's own impetus.
Are you following where this is going?
The bloody diodes buried in the solenoid casing are open circuit, so fit a couple of diodes in and [:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)][:)]
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Oooooooooh!!!!
Something I never even considered! Yes of course, you cant apply a pulse width modulated DC signal to an inductor and expect it to behave properly if it doesn't have a back EMF clamping diode. In fact, the EMF could potentially damage the output of the computer...
Funny thing is, only a week ago while reading my printout of the HA2 manual I was commenting to Dad "look at this, they've burried the back EMF clamping diode in the HA control block - why don't they put it at the other end of the cable in the HA computer in case it ever needs replacing ?" never even OCCURED to me that I should check the diodes...
[:D][:D]
So where did you fit the diodes and what kind ? Hopefully some well rated ones that won't ever conk out again...did you notice any increase or decrease in the whining noise from the solenoids ?
I will definately be checking mine on the weekend to see if they are ok. Depending on the mechanical sensitivity of the solenoid its definately possible that on some solenoids they may stay open SOMETIMES if the diode is faulty, but not reliably...
It could be related to my intermitant hard ride problem, and could also be related to what I described where it drops again after lifting up in the morning - the initial high current pulse happens while there is not enough hydraulic pressure to open the valve, then it drops back to the PWM current, then some time later the pressure reaches enough to operate the valve, but if by then the solenoid is barely open due to a faulty diode...
Glad to hear you finally got to the bottom of it...
So how do you find the ride now ? Should be something of a revelation if my experience is anything to go by. (Mine was stuck in hard at the back when I got it due to the middle sphere)
By the way, now that its working, I don't suppose you find the rear TOO soft ? If you do a bounce test does the body overshoot the mark on the return ? Or does it come to rest nicely with critical damping ?
Regards,
Simon
bernie
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Post by bernie »

I've only fitted them thus so far
Image
just to prove a point
Red led front
Yellow back
I used 1N5408 diodes
Yes the solenoid/valve made noises I'd not noticed before.
And yes the ride is a lot better. I think I'll now experiment with the spheres to make it even better
bernie
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Post by bernie »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by NiSk</i>

Great Bernie, now draw us a diagram!
//NiSk
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
OK I'll do that
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Mandrake
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Post by Mandrake »

Hi Bernie,
An update on my HA2 gremlin chasing - I finally got a chance to test the diodes in my HA2 solenoids and they are ok. [:)]
The coil resistance is about 5.6 ohms, I connected 12 volts to them via a 15 ohm resistor, and the correct way around this results in about 2.8 volts across the coil and the wrong way around about 0.8 volts, so fair to say that the diodes are ok.
However in the process I learnt a VERY INTERESTING fact that we were not aware of - as you know, the computer applies full 12 volts for about half a second to switch the solenoid on faster, then drops back to about 2.5v average (using PWM) to keep it engaged without too much heat dissipation.
I measured it and it was indeed around that, varying between 2.4v and 3v depending on circumstances. (Engine running or not, etc)
During my testing with the 15 ohm resistor and 12v battery, (which applies about 2.8v to the solenoid - slightly more than the hold voltage from the computer) I discovered that the 2.8v will NOT engage the solenoid by itself! Not slowly, not at all! Not on either the front or rear one.
So, the half second burst of 12v is actually NECESSARY for the solenoid to switch at all! If I connected the 15 ohm resistor and battery, then momentarily shorted out the resistor, the solenoid would switch and the resistor was enough to keep it engaged once engaged.
This small piece of information has serious ramifications - if there is a loose/intermitant or high resistance connection to either solenoid then I can see it would be quite possible for the solenoid to drop out whilst the computer is in the soft mode due to - for example - the car hitting a bump and jiggling a loose connection resulting in a momentary loss of power to the solenoid, causing the solenoid to drop out, however the computer is still supplying power to the solenoid and thinks everything is ok.
You're now in a situation where the computer thinks the suspension is in soft, but the solenoid (highly likely only one of them at a time) has dropped back to hard, and it will STAY THAT WAY until the computer next decides to switch to hard and back to soft again. (Thus providing the needed 12v pulse to kick the solenoid back into action again)
So it's critically important for there not to be any poor connections to either solenoid. I had already given the solenoid plug for the front solenoid and the plugs on the HA2 computer a good spray of LPS1 a few weeks ago, but had not yet done the solenoid plug for the rear until today. (What a b*****d of a thing to get at too...)
So that is discovery one. Now for discovery two.
I had noticed that the Normal/Sport switch light was very dim and also that it seemed to change a lot from time to time, sometimes it was reasonably bright, other times it was almost impossible to see it so I thought there might be a bad connection in there.
Looking at the circuit for the switch something very interesting comes to light - its a 3 pole switch with two normally closed contacts and one normally open contact, and the pole that switches the light on, and the one that sends the signal to the HA2 computer are two seperate poles.
Furthermore the switch is wired such that open circuit means sport mode while shorted means normal mode, using the normally closed contacts. This means that ANY failure of this pole of the switch or a bad connection between the switch and the computer will put the computer into SPORT mode.
So if this happened you would see the sport mode light on all the time and notice the problem, right ? WRONG!
The light runs of the normally open pole of the switch, and is independant of the signal to the computer!
The upshot of all this is if you were to disconnect the wire to pin 2 of the switch assembly, (or the switch contact was faulty, or there was a bad connection etc) the sport mode light would switch on and off with the button normally but the computer is ALWAYS in sport mode! Thus a hard ride much more often than in normal mode.
I ended up taking the switch out and taking it completely to pieces. While I had it apart I removed the bulb and repositioned it so that it was right up the top of the orange tube that it sits in, and cleaned the contacts where the wrapped bulb legs touch the PCB, and also cleaned the switch contacts and plug contacts with LPS1 then reassembled it.
Quite a fiddly little job but the bulb is now relatively bright all the time, (so far) instead of being nearly impossible to see sometimes.
If a poor contact could cause the bulb to be very dim, I don't see why it couldn't have been making the computer stay in sport mode regardless of switch setting, on some occasions...
I've only driven the car for about 15 minutes since doing this, but so far I havn't noticed any of the intermitant hard ride issues I've been having lately, so fingers crossed [:)]
Regards,
Simon
bernie
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Post by bernie »

Hi Simon, sorry been a bit preoccupied today.
Your findings together with the 'diode problem' point to a system that does not seem to be too robust.
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Mandrake
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Post by Mandrake »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by bernie</i>

Hi Simon, sorry been a bit preoccupied today.
Your findings together with the 'diode problem' point to a system that does not seem to be too robust.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Well, the wiring of the switch is certainly not robust in design. If I was designing it first of all I would have used open circuit to represent normal mode, not sport mode, so that faulty wiring would keep it in the more comfortable mode.
Secondly I would have designed it so that the bulb ran off a direct feed from an output from the computer without going through the switch contacts, and have the computer switch the bulb on and off with a transistor in response to the input signal from the switch - that way if the bulb would truely indicate what the computer thought, and not just the position of the switch...
Regards,
Simon
PS I might have jumped for joy too soon - went out for a drive this morning again, and have harsh ride in the front again. [}:)] I wonder if I'll ever get to the bottom of this. After changing the LHM a few days ago the ride was like a magic carpet, then a couple of days later its deteriorated back to its bad old self again. [:(]
Regards,
Simon
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