Headlight flickering and aircon blower " run spiking "

[KennyX]

Hi all, i really running out of idea to find out the real issue with my 1.4l berlingo.


She start developed weird problem after 200k of mileage.
No more clock display, havent check on the BSI fuse box
Headlight flickering, more obvious when press on gas pedal.
Air con blower also affected, light goes dim / blower fan slow down at same pace.

What i check so far
Battery is ok, 1.23 when engine off, 1.45V when run. Quite stable even if revving up the engine.
Alternator, no slipping belt, i tried unplug the charging cord, run solely on battery also seeing the same problem
Loud relay clicking in the BSM fuse board, i'm not sure which relay is making noise, it seems like all of them dancing together, it clicking same pace with the light / aircon fan .
BSI reboot done, no help

Ground on MC11 & MC13 been check and looking good.
No noticeable potential different between car body and battery negative terminal, compare with a digital multimeter and test on the positive terminal.

Headlight is ok if engine is not running.
I tried pull out the body van signal connector ( EP1 connector on BSM ), Headlight stay On, wiper move but only 1 time, aircon not working ( i guess BSI is controlling everything on the accessories, headlight on is due to safety design incase connection problem between BSI and BSM, headlight is bright and steady , no dimming problem under this mode.

I guess the BSM is reading VAN signal with the small processing board on the BSM fuse box circuit and convert the signal into ground switching mode to trigger the targeted relay.

The relay will clicking even if you not turning on any light or aircon, When engine is running
So far i never take out the BSI module yet, i tried and fail to unplug the center power supply connector, it seems the red color things that hold the connector is stucked and refuse to move out further, other connector is fine which i can press it out easily with a flat screw driver.

Any pro here have any idea what is the best possibility to cause such problem ?

KennyX

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Could be a faulty BSM ?
Loosen wire between BSI & BSM ?
Or simply faulty BSI ?

[Ol'Jeffers]

It sounds as if the voltage rectifier on the alternator may be faulty.
But I'm not a 'pro' and I would be interested in the response that one of our wizards
will give. Excessive alternating current maybe the cause.

[KennyX]

Sharing is caring bro,
Thx for the idea, but how to check and justify for excessive current ?

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I put aside alternator because headlight work fine without any dimming when i unplug the EP1 connector which it carry and transmit the VAN signal from BSI to BSM.

[Ol'Jeffers]

It's difficult to isolate and measure the amount of AC that is on a DC line.
Have you tried measuring with a good quality Multimeter on both DC and AC ranges?
To be honest I'm not too sure that would give any useful information. You could also try measuring
the voltages on another Citroen/Pugeot which is running correctly.
I'm now out of ideas and my brain hurts!
An expert here will no doubt be able to tell you what the next step should be and he will also say that I'm
talking rubbish!!
Stay tuned!!

[dumdum]

a battery itself does a good job of smoothing ac ripple that alts give out, i would have said its either a diode is dead in the alt or the regulator is on its way out, and isnt responding as quickly as it should (id normally say look for blowing bulbs, but its a pug so fairly common lol) the only proper way to test it is renove alt and bench it i would think unless someone has a very posh alt tester for in situ never come across one that good tho, a decent 60mhz scope may show more connected across 12 tho, that would pick up minute spikes and may show your issue??

[KennyX]

I dont have an oscilloscope at the moment, high speed voltage spike not possible to measure with my digital multimeter.

my next move will be find a way to take out the bsi module make sure no surface contamintation on the circuit board due to moisture, also try to check the continuilty or wire resistance of the van signal cable, totally 3 of them.

[KennyX]

I finally manage to unplug all the BSI connector and pull it out,
i found some strange stain inside the " EP " connector

[Image: jgtq.jpg]

and more
[Image: t39f.jpg]
Oh God, Why Me !?


I clean it up with some spirit and brush work, but the result is disappointing, it didnt fix anything , could be the board is already damaged ?

I'm thinking of dismantling the bsm board and modify the trigger signal path for headlight and air con relay, adding in a RC delay circuit might be helpful to prevent relay from clicking too often

[Rustscrat]

As you say, check the two comm lines & Comms positive supply line for continuity and shorts to earth.
Also check that you have a good supply between pin 9 (+) and pin 5 (-) of PP2 (grey plug) of the bsm/Psf. (with ignition on)
If you can obtain another Bsm/Psf to try in, I would do this as these are not coded and are interchangeable as long as you get the right Bsm number - "B2, B3" etc.
Let us know what you find. :thumbsup:

[KennyX]

Im getting another set from ebay as spare and as my new experiment. Lol
By the way, after 2 hour of research on the bsm circuit.
I found that the comm+ is the individual supply for the decoder, relay powering power is taken from ignition input.
2 earth on the ep1 connector, pin 3 shared with pm1 and pin 8 individually solely for the darlington transistor and earth for relay switching. It is different from service manual which i dl from the forum .
i will check the ignition input voltage later.

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I wonder the signal output from steering stalk is all or nothing type or can signal .
By pass bsi module it seems not that difficult afterall.

[KennyX]

I found a part of the problem, the darlington transistor need 5V TTl signal to turn on the relay. I found the signal sometimes drop to 4v in fraction of a second, my DMM barely can read that drop out voltage and it is same pace with relay clicking.

[Image: q1ug.jpg]
The darlington transistor, ULN2003

The driving signal for this transistor is coming out from another IC called " TSS-1016-A " which this the core component to read VAN data from BSI and action according to the signal.

[Image: 4eg6.jpg]
The IC TSS-1016-A

I have no clue on the VAN data command, i should use some decoder to read the incoming VAN signal and look for losses before doing anything on hardware.
Got no patience to do that, so since the relay clicking problem is because of the unstable driving signal. My initial thought was to stabilize the signal, the RC circuit seems fit well.

I download the datasheet of the ULN2003 and found out that the input resistance is well over 2kohm, nice so i dont have to use another resistor to limit the current's flow.

[Image: ocgi.jpg]

Solder 2 capacitor on the transistor's input and ground. put the bsm back into my car and test it.



The result is ..........
SWEET !

To fit the board back into the BSM plastic housing is impossible , not enough space for the capacitor .
So i cut a few wire to relocate the capacitor to other place which will not cause clearance problem with the casing

here how its look like
[Image: 6lc7.jpg]

This is just a temporary fix for my problem, i will try to get a spare BSM unit from ebay and try to compare my existing unit to find out who is the real trouble maker.

KennyX