Cruise Control problem

[aliking]

Hello all

The cruise control in my 1992 500E is not working, i searched the forum for the causes and im not sure of what to check exactly.

Thats what i checked:

• The cruise control arm is working and i checked it using star diagnosis.
• The ETA is good, no error codes on star
• The brake light switch is new geniune working good
• The E-Gas module is good with no error codes on star
• The wheels are the original 16" wheels, im not using the evo wheels anymore

now i need assistance about what else to check? Did i miss anything

thanks in advance

 

[gsxr]

Are the tires the same size front & rear? Does the cruise control work at low speeds (40kph)?

 

[aliking]

Are the tires the same size front & rear? Does the cruise control work at low speeds (40kph)?

Hello and thank you for teply gsxr, yes the tires size 225/55/16 front and rear, no its not working at all.

 

[Jlaa]

Do you have any brake light bulbs that are burnt out or not incandescent bulbs? Cruise Control relies on the brake light bulbs working. If the car determines that there's no brake light bulbs then the cruise won't activate.

 

[aliking]

Do you have any brake light bulbs that are burnt out or not incandescent bulbs? Cruise Control relies on the brake light bulbs working. If the car determines that there's no brake light bulbs then the cruise won't activate.

All the brake light bulbs are working, but i added a third stop light on the rear window, and sometimes when i press the brake pedal i see the burnt lamp warning light on the dash for a second then disappear, all the lamps are Osram with the accurate watt power. Should i disconnect the third stop light?

 

[Jlaa]

What happens if you remove the bulb from the 3rd stop light? Do you still get the bulb out warning light?

 

[aliking]

What happens if you remove the bulb from the 3rd stop light? Do you still get the bulb out warning light?

No, and if its burnt i will not see the bulb out warning light,

 

[Jlaa]

If you wired the 3rd brake light in parallel with one of your existing brake light then you are forcing your underhood bulb out warning relay to sink 2x the amount of current that it is designed to sink on one leg ..... assuming your 126.542.03.32 (assuming you have Euro market car) is not fried from that, then does the removal of that third bulb restore cruise control operation?

I don’t really expect it to restore operation, but IIRC the cruise “computer” needs to see a path to ground (thru a bulb filament) to activate. If there is no path to ground it will not activate ......

 

[aliking]

If you wired the 3rd brake light in parallel with one of your existing brake light then you are forcing your underhood bulb out warning relay to sink 2x the amount of current that it is designed to sink on one leg ..... assuming your 126.542.03.32 (assuming you have Euro market car) is not fried from that, then does the removal of that third bulb restore cruise control operation?

I don’t really expect it to restore operation, but IIRC the cruise “computer” needs to see a path to ground (thru a bulb filament) to activate. If there is no path to ground it will not activate ......

Thank you Jlaa for great explain,
Ur correct, i wired the 3rd brake light from the left side existing brake light, now i will try it after removing the third brake light Wiring, if its still not working, i will try another used 126.542.03.32 and see what happens, yes my car is a euro market car.
Thank you so much

 

[aliking]

If you wired the 3rd brake light in parallel with one of your existing brake light then you are forcing your underhood bulb out warning relay to sink 2x the amount of current that it is designed to sink on one leg ..... assuming your 126.542.03.32 (assuming you have Euro market car) is not fried from that, then does the removal of that third bulb restore cruise control operation?

I don’t really expect it to restore operation, but IIRC the cruise “computer” needs to see a path to ground (thru a bulb filament) to activate. If there is no path to ground it will not activate ......

Hello Jlaa and thank you again
I did the following with no luck, the cruise control still not working
1- removed the 3rd brake light harness
2- changed the brake light bulbs with new ones
3- cleaned the rear lights electric board

do you suggest anything else?

 

[Jlaa]

I'm sorry I don't know ---- I was just trying to rule out obvious / easy solutions. Have you dived into the ETM yet? 24 Electrical Troubleshooting

 

[Provet]

Hello all

The cruise control in my 1992 500E is not working, i searched the forum for the causes and im not sure of what to check exactly.

Thats what i checked:

• The cruise control arm is working and i checked it using star diagnosis.
• The ETA is good, no error codes on star
• The brake light switch is new geniune working good
• The E-Gas module is good with no error codes on star
• The wheels are the original 16" wheels, im not using the evo wheels anymore

now i need assistance about what else to check? Did i miss anything

thanks in advance

Next clean all sensors at wheels, then check out the thread for the 3rd brake light mod on here someone did in reference to the light relay that correspones to euro vs us type relays with third light., the dash light should not come on if bulb is working as Jlaa said may be parrellel.

 

[aliking]

I'm sorry I don't know ---- I was just trying to rule out obvious / easy solutions. Have you dived into the ETM yet? 24 Electrical Troubleshooting

Thank you Jlaa and i really appreciatw ur help, i will take a look at the ETM to know more about this problem, thank you again

 

[aliking]

Next clean all sensors at wheels, then check out the thread for the 3rd brake light mod on here someone did in reference to the light relay that correspones to euro vs us type relays with third light., the dash light should not come on if bulb is working as Jlaa said may be parrellel.

Thank you Provet, i will clean the front abs sensors and the rear abs/asr sensor and reply to you again if that fixed the problem, but in STAR diagnosis i dont see any error code, current or stored.

 

[Provet]

I learn something about when ihad my STAR hooked up, it did not see code either. So when cleaning. Clean the vanes on the hub also, not just the sensor. Mine where clogged with grimes, so when car moving not getting full read. But if you do a burn out on slick surface and asr triangle light up you now rears are reading, usually fronts are the dirty most. But honestly i thing your trouble lies in the brake light set up, make sure that swicth behind brake pedal good too its easy to forget to hook up that third wire that goes on the switch before the actaul two prong connector, that one go to module, cruisewont work without it also. Good luck!

 

[Jlaa]

But honestly i thing your trouble lies in the brake light set up, make sure that swicth behind brake pedal good too its easy to forget to hook up that third wire that goes on the switch before the actaul two prong connector, that one go to module, cruisewont work without it also. Good luck!

@Provet has a good observation about the brake light switch. Here is some further info:

Mercedes-Benz W124 Brake Light Switch Replacement | 1986-1995 E-Class | Pelican Parts DIY Maintenance Article

A faulty brake switch can cause all kinds of problems; replace yours with help from this article.

www.pelicanparts.com

 

[aliking]

I learn something about when ihad my STAR hooked up, it did not see code either. So when cleaning. Clean the vanes on the hub also, not just the sensor. Mine where clogged with grimes, so when car moving not getting full read. But if you do a burn out on slick surface and asr triangle light up you now rears are reading, usually fronts are the dirty most. But honestly i thing your trouble lies in the brake light set up, make sure that swicth behind brake pedal good too its easy to forget to hook up that third wire that goes on the switch before the actaul two prong connector, that one go to module, cruisewont work without it also. Good luck!

Thank you for the info
I will first clean the sensors and try again
If that didnt solve the problem i will check the brake light switch.
will tell all the updatea here

 

[aliking]

@Provet has a good observation about the brake light switch. Here is some further info:

Mercedes-Benz W124 Brake Light Switch Replacement | 1986-1995 E-Class | Pelican Parts DIY Maintenance Article

A faulty brake switch can cause all kinds of problems; replace yours with help from this article.

www.pelicanparts.com

Thank you, will check that also

 

[Provet]

Thank you Provet, i will clean the front abs sensors and the rear abs/asr sensor and reply to you again if that fixed the problem, but in STAR diagnosis i dont see any error code, current or stored.

Status update?

 

[aliking]

Status update?

Hello mr Provet
I cleaned the abs sensors, lot of dirts on them, but still same problem, the cruise control not working, i also reinstalled the 3rd stop light and the evo wheels bcoz removing the 3rd stop light and using the original 16" wheels didnt solve the problem
Do you any other suggestions?

 

[Provet]

Try something for me, press chain light button on the dash in park. See if it turns on and off properly. When on press down on the cruise lever to see if light goes off, when off, do the same thing to see if turn on. If this is happening its your switch it self, not good contact somewhere

 

[aliking]

Try something for me, press chain light button on the dash in park. See if it turns on and off properly. When on press down on the cruise lever to see if light goes off, when off, do the same thing to see if turn on. If this is happening its your switch it self, not good contact somewhere

Hello mr Provet
Please can you explain more, i guess u mean:
1- press the chain light button, it should turn on with red light on
2- press the chain button again, it should turn off with red light off
3- turn on the chain light button again and press down the cruise control stick, the red light on the chain button should turn off

after that starting from (when off, do the same thing to see if turn on) i didnt understand that step,

thank you

 

[Provet]

Thats correct, if the switch turns off that red light on snow chain in any dirrection except cancel, something is wrong with switch contact points

 

[Provet]

Or turn red light on when its off, vise versa

 

[aliking]

Or turn red light on when its off, vise versa

Hello again mr Provet
I turned the engine on, pressed on the chain button and the red light turned on, did the same thing to turn it off and worked 100%
and after i turned it on, i moved down the cruise control stick and nothing happened, the red light still on, moved it all the directions and also nothing happened till i turned the switch off by pressing on it directly.
Is that ok?

 

[Provet]

It works as suppose too, we know switch is good from star also, its ruled out. Brake lights ruled out, brake switch ruled out, sensors cleaned. i would assume nss ruled out from egas codes. Only thing i can think of is the asr module is stuck in some mode not allowing egas to engage cruise. I believe if i remember i put snow chain on and drove past 70km to see if it cut off by itself and when it did i put cruise on and it had start working again. It was awhile back but i know these two things was linked somehow. If that not work we haveto try different modules to make sure. In the asr module i assume you seen the speeds of all sensors when driving?

 

[aliking]

It works as suppose too, we know switch is good from star also, its ruled out. Brake lights ruled out, brake switch ruled out, sensors cleaned. i would assume nss ruled out from egas codes. Only thing i can think of is the asr module is stuck in some mode not allowing egas to engage cruise. I believe if i remember i put snow chain on and drove past 70km to see if it cut off by itself and when it did i put cruise on and it had start working again. It was awhile back but i know these two things was linked somehow. If that not work we haveto try different modules to make sure. In the asr module i assume you seen the speeds of all sensors when driving?

Hello again mr provet, today i did exactly what u said, drove the car with snow switch on, when exceeded the speed and the red light turned off i pressed down the cruise control stick but sorry to tell nothing happened, the cruise control didnt work.
I will try dufferent asr module and see if it works, i will also connect the star diagnosis and see the signal from the speed sensors. Thank you again for keep giving me advices in my problem, really appreciate that.

 

[Provet]

Damn, i can't call this one . . . Also when in star i know see make sure idle speed contact switch/saftetycontact is working. This could be eta or module fault

 

[aliking]

Damn, i can't call this one . . . Also when in star i know see make sure idle speed contact switch/saftetycontact is working. This could be eta or module fault

I will scan and send to you all the readings, i started thinking to replace the eta