Speed pulse c180 esprit 1997 (W202)

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
Help !
trying to find the speed pulse wire in this car. read most of the previuos posts and cant seem to find a pulse at all.

obvious first place was the iso plug at pin 1 (green/mauve) but cant find a pulse !
the wire is at 12volts with the ignition on and as soon as the car moves it drops to 6.5 volts and stays there whatever speed until the car comes to a hault.

also tried looking in cable duct at drivers front door post for a green/white wire but it doesnt cary a pulse stays at 0volt until brakes are aplyed and goes up to 0.7volt (obviously not that one then)

next place was direct from the diff sensor and found a pulse but its such a low voltage with a very small change of voltage to speed ratio that it aint good enough for the needed purpose ? ( you guessed a taxi meter)
Need to find a pulsing voltage between 0.0volt / 12.0volt ?
surely someone knows ??.
 

andy_k

MB Enthusiast
Joined
Apr 23, 2003
Messages
5,204
Location
Bexhill, East sussex
Car
Alfa GTV 3.0
back of the speedo? cruise module?

either of these should carry a useable pulse - on a W124 or W201 the speed pulse wire is yellow and green at these locations

hth

Andy
 
OP
OP
T

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
thanks for the reply andy
knew it was that on the w201 as thats what I had previously (wonerfull bit of engineering), but the wiring on the w202 is diferent,
didnt realy want to go and take out the steering wheel + (airbag) to get at the back of the clocks
but might have too !
 

Only me

New Member
Joined
Oct 2, 2006
Messages
15
Hi,

Possibly not much use - BUT!

I have a c200 W202 and went thru this recently.

The green/mauve wire on iso plug position 1 is a speed pulse wire on mine - I spent some considerable time trying to locate a useable signal from various locations before I realised that the green/mauve wire had been cut just a few inches from its entry point into the din plug :mad: !

After I reconnected the ends, the speed pulse I needed was fine.

You might just want to check that the wire is in one piece

Good Luck!

GB
 

GRAV888

MB Enthusiast
Joined
Mar 5, 2003
Messages
6,324
Location
Rochester and Lancashire
Car
2017 CLA 180 AMG in Black (mine) 2018 GLA 200 SE in Black (wifes)
tacsi said:
thanks for the reply andy
knew it was that on the w201 as thats what I had previously (wonerfull bit of engineering), but the wiring on the w202 is diferent,
didnt realy want to go and take out the steering wheel + (airbag) to get at the back of the clocks
but might have too !
You can remove the cluster without touching the steering wheel.
Either get the propper cluster removal tools from the stealers, or remove the panel by the bonnet release, put your hand up behind the cluster and push them out. Mind your knuckles though.
 
OP
OP
T

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
cheers for the reply
I am geting a voltage reading from this wire at pin1, 12volt whith ignition on (stationary) & 6.5volt when on the move.
so assume that it's not been cut ?
but will check again to have a look just in case I missed something obviuos
 

GrahamC230K

MB Enthusiast
Joined
Jul 14, 2002
Messages
9,755
Car
Audi A3 & S4 quattro
Are you telling us you believe the speed pulse is no good based on the voltages you have measured or have you actually reason to belive there is an issue having connected it to some equipment that uses the speed pulse?

As far as I know the reading you have measured are normal.

See here, someone made the same assumption:

http://www.mbclub.co.uk/forums/showthread.php?t=2196
 

Shude

Hardcore MB Enthusiast
Joined
Jun 1, 2002
Messages
13,882
Location
Cheshire
Car
CLK55 AMG
GrahamC230K said:
Are you telling us you believe the speed pulse is no good based on the voltages you have measured or have you actually reason to belive there is an issue having connected it to some equipment that uses the speed pulse?

As far as I know the reading you have measured are normal.
Graham is correct, the voltage is probably normal but in order to measure the speed pulse you would have to connect the wires to an oscilloscope!
 

Alfie

Authorised Forum Sponsor
SUPPORTER
Joined
May 5, 2004
Messages
7,854
Location
Surrey/Cotswolds
Car
W169 A, W205 C, W451 smart
tacsi said:
cheers for the reply
I am geting a voltage reading from this wire at pin1, 12volt whith ignition on (stationary) & 6.5volt when on the move.
so assume that it's not been cut ?
but will check again to have a look just in case I missed something obviuos
Fix up a 12volt bulb to the speed pulse and if it varies in intensity as you drive, then the speed pulse is working. Simple.
 

GrahamC230K

MB Enthusiast
Joined
Jul 14, 2002
Messages
9,755
Car
Audi A3 & S4 quattro
Alfie said:
Fix up a 12volt bulb to the speed pulse and if it varies in intensity as you drive, then the speed pulse is working. Simple.
Hmm. Is that fact or theory? If a bulb was going to vary the voltage would vary. The voltage remains contstant I believe.
 

Shude

Hardcore MB Enthusiast
Joined
Jun 1, 2002
Messages
13,882
Location
Cheshire
Car
CLK55 AMG
GrahamC230K said:
Hmm. Is that fact or theory? If a bulb was going to vary the voltage would vary. The voltage remains contstant I believe.
Light from incandescent bulbs will fade as the frequency of the pulses decrease, probably a bit like how dimmers work on home lights (classy! :D).
 
OP
OP
T

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
GrahamC230K said:
Are you telling us you believe the speed pulse is no good based on the voltages you have measured or have you actually reason to belive there is an issue having connected it to some equipment that uses the speed pulse?

As far as I know the reading you have measured are normal.

See here, someone made the same assumption:

http://www.mbclub.co.uk/forums/showthread.php?t=2196


Cheers Graham
had already read the link you supplied + others regarding speed pulse.
was acctually questioning if there should be some visible change in voltage in speeding up/slowing down ?
I not had this problem when finding speed pulses using a volt meter on other vehicles ! (old merc's, VW's, BMW's)
the mulitymeter used is not your usual £2.99 job but an expensive £100 one, so surely it would do the job better than a 0.50p bulp.
have connected the wire to the equiptment but not calibrated the taxi meter as I dont belive there is a pulse ?
Shude could be correct that you need an oscilascope to read the pulses !
in my way of thinking is that if they were that frequent that they cant be read on a volt meter, then surely my taxi meter should be going nuts and going up at a rate of ££££ per wheel revolution ?!
as it's only calibrated to only 5 pulse's per wheel revolution ?.

so can anyone tell me how many pulse's per wheel revolution on the w202 ?
what sort of voltage's should I be getting ?
 

GazCaff

MB Enthusiast
Joined
Apr 30, 2006
Messages
1,051
Location
1123 6536 5321
Car
'05 E280 CDI Avantgarde
If I was going to test the signal from the speed pulse I would measure for AC rather than DC voltage myself. An educated guess from myself would suggest that 12v gives the cruise, abs etc a logic state of 1 which tells the various systems the vehicle is stationary and that the system is serviceable. On the move the pulse train drops down to 6v to act as a base voltage level that the speed pulse is imposed onto. Chances are the pulse will be half-wave rectified in nature for this reason so the best method to measure would be with the AC setting on the multi-meter.

If the Voltage is 0v then obviously the system is off or a fault state exists.

Hope I made sense. Like I say, its a guess but I don't think I'm far off the truth.

Edit, the automatic sound on my stereo works fine off the speed pulse on my 202.
 

HughJarse

MB Enthusiast
Joined
Sep 13, 2006
Messages
1,035
Location
North East
Car
c250
GazCaff said:
If I was going to test the signal from the speed pulse I would measure for AC rather than DC voltage myself. An educated guess from myself would suggest that 12v gives the cruise, abs etc a logic state of 1 which tells the various systems the vehicle is stationary and that the system is serviceable. On the move the pulse train drops down to 6v to act as a base voltage level that the speed pulse is imposed onto. Chances are the pulse will be half-wave rectified in nature for this reason so the best method to measure would be with the AC setting on the multi-meter.

If the Voltage is 0v then obviously the system is off or a fault state exists.

Hope I made sense. Like I say, its a guess but I don't think I'm far off the truth.

Edit, the automatic sound on my stereo works fine off the speed pulse on my 202.
Woh?? Ive got to be honest, its nice being part of a forum where people who know what theyre talking about give answers.

At first while reading this thread I thought theres no way that MB would have a speed pulse that was a simple change in Volts. After reading your reply I realise they dont!
Haven't the foggiest what you mean though :)
 
OP
OP
T

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
Originally Posted by GazCaff
If I was going to test the signal from the speed pulse I would measure for AC rather than DC voltage myself. An educated guess from myself would suggest that 12v gives the cruise, abs etc a logic state of 1 which tells the various systems the vehicle is stationary and that the system is serviceable. On the move the pulse train drops down to 6v to act as a base voltage level that the speed pulse is imposed onto. Chances are the pulse will be half-wave rectified in nature for this reason so the best method to measure would be with the AC setting on the multi-meter.

If the Voltage is 0v then obviously the system is off or a fault state exists.

Hope I made sense. Like I say, its a guess but I don't think I'm far off the truth.

Edit, the automatic sound on my stereo works fine off the speed pulse on my 202.







Right !
belive it or not what you were explaining made sense to me !
so today I dug out my trusty old analog volt/ohm meter,and got a bit more sense out of that !
At a real snail's pace I can now see the needel flicker !! though they do seem eratic (not every pulse read's the same voltage) ??
but as the car moves slightly faster the pulses become either undreadable or so fast that the voltage looks constant !
this happens even if I use the AC volt reading.



so does any one know ?

how many pulses there are per wheel turn ?

what voltage should I be reading ?



p.s (bloody electronic fandagled gadgetry)

pps. MY GOD!! (starting to sound like my dad)
 
OP
OP
T

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
OK !

Eventually went and riped every thing out and started all over again !
Ahaa! found one problem a broken wire in the equiptment I was trying to fit !
so redone the connection and tried it again !.
NOTHING !
(SO GOT REALLY FED UP)
in a bad mood just slapped the iso plug back in the radio, and the radio back in the dash and went indoors to finish xmas booze off !
 
Last edited by a moderator:
OP
OP
T

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
Eurika

:bannana: WELL WOULD YOU BLOODY BELIVE IT ???


the very next day after polishing off the last of the xmas booze :p

jumped in the car drove off and noticed that the equiptment switched on :confused: (should do this when properly connected)
so tried the meter and it works:bannana: . well sort of, you wouldnt want to pay that rate belive me ! (£18.76p a mile)

got me thinking here :confused: ! was it the bad tempered slamming ??
or a conspiracy ! ( NAH! :eek: )
so the only other explenation I come up with is that previously I'd been testing with a cut single end of the wire and the bad temper made me put everything together to make the circuit compleete :D.

even though I still need to put a signal amplifier in line and also calibrate the meter .


for any one else that might need to read this in the future

the pulse volts are so low and so fast that they are vurtually impossible to read with standard equiptment (they look constant)

LESSON

DONT !
over look the obvious !

NEVER !
forget with modern cars it's not electric's !, but ELECTRONIC'S !!


AND !
if at the end of you'r tether thow all toy's out of the cockpit and hit the bottle .:rolleyes: :crazy:







OHH! and by the way thanks to all who gave thier opinion upon this request for help.
 

richard

Authorised Forum Sponsor
SUPPORTER
Joined
Jun 10, 2002
Messages
6,256
Location
Berkshire, UK
Car
MY04 SL55, MY18 GLC63s
I know you're sorted now, but

> so can anyone tell me how many pulse's per wheel revolution on the w202 ?
48

Richard
 
OP
OP
T

tacsi

Member
Joined
Dec 21, 2006
Messages
41
Location
Mid Wales
Car
1989 190E + c180 esptrit (w202)
richard said:
I know you're sorted now, but

> so can anyone tell me how many pulse's per wheel revolution on the w202 ?
48

Richard








HI Richard

cant realy tel you exactly how many m8 !
but it was mentioned previously that there were 48 pulses per wheel revolution.
cant confirm this !, but going by the fact that the meter was previously calibrated for only 5 pulses and that in this car it was counting approx ten times that, I would hazard a guess that this could be quite true !
as my taxi meter was calibrated over a 1 mile distance I can only tel you that there were 2895 pulses f*** knows how many wheel revolutions that was !, not in the habit of driving with my head out of the window counting wheel turns, ( too busy shouting abuse at other drivers when I stick my head out of the window):rolleyes: .


OOOPS !
just realised that you were making a statement ! and not asking a question ( DOH!)
 
Last edited:

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top Bottom