r129 1991 500sl power hood

[cossiewes]

i have just purchased a 1991 500sl in good condition but has been parked up for two years and the power hood does not operate .i have checked the fuses and tested that i have got power to the motor and there is.i would be very gratefull if anybody would have any suggestions off why it is not working or what to try next to make it work thanks wez.

 

[landover]

It might be something as simple as the motor sticking . Get someone to operate the switch and give the motor a tap with hammer. Not too hard.

 

[davidsl500]

You could try raising the hood manually to make sure all the mechanical bits are free. There is a procedure for this in the drivers handbook

 

[davidsl500]

Whilst thinking about it, do your windows open slightly when you press then button? The first thing that happens is the windows lower out of the way, the antiroll bar goes down (if up) and the hood starts to rise. If the windows don't lower try lowering them first or open both doors.

 

[cossiewes]

have tried lowering windows and doors open still nothing.the hood is stuck in the up position at the moment.i read somewhere that there are sensor points that if these are not registering properly then will not allow the hood to go down or up but have no idea if this is true or where they would be any advice much appreciated thanks wes

 

[davidsl500]

There are sensors that check the hood is locked properly - if not then the hood button flashes and there is an audible alarm if you try to drive off. I would presume that these must be located close to the locking pins on the leading edge of the hood where it joins the windscreen.

If it has been up for two years maybe the locking pins have seized on and I presume that if they are then then the motor would not operate?

The hood will only operate with the key in ignition position 2 and you do have to pull it back and hold it - sorry if this is a bit basic for you but I dont know whether you are familiar with the operation at all.

It is possible to put the hood up manually and lock it therefore I presume it is also possible to unlock it and put it down manually as well, Mercedes supplied a combined open end / hex socket spanner to carry out this procedure.

Do you have the owners manual for the car - if not i can scan the relevant pages in mine and e mail them to you.

 

[Arnie]

1. The hood will only operate with sufficient battery voltage or otherwise with the engine running.

2. There are about 6 microswitches which govern its operation.

3. A fault is usually accompanied by a flashing light (fast or slow) on the switch.

4. If your windows don't drop automatically first, then the hood may not operate. In that case, your windows may need to be reset (particularly if the battery has been disconnected). They are reset by operating them with the door closed and making them go all the way up and down a couple of times. Then try the hood swicth again.

5. See if you can hear the sound of the hydraulic pump motor running when the swicth is operated.

6. Check you have sufficient hydraulic fluid in the system , that it has not leaked.

7. As suggested try opening it with the manual lever in case something is stuck.

8. Does your rollover bar operate from the dash button? (I think this uses the same hydraulic system)

 

[kkmfo]

hood

check your battery first.
hood and all electrics are very sensitive to low battery voltage.
The battery may not be the problem, but it is the place to start, particularly if the car hasn't moved for 2yrs.