jeffjensen121

I took my 1994 e320 cabrio to the MB dealer to check codes in my pursuit of fixing soft top(won't lower). The only code shown is low voltage. Everything works or tries to work. Chime chimes, all windows go down, deck unlatches and that is where the process stops. This with the car in park or neutral, running, or off. There are no fluid leaks. Does anyone have any advice as to where I should start checking to eliminate this problem? could it be as simple as the voltage regulator? maybe the hydraulic switches in back?

RBYCC

It appears that all the initial mechanical devices are functioning but the hydraulic pump is not working.

Start the engine, keep it in park and bring your RPM up to 2000+.
Try to see if the roof will work.

Still not working, then pull the right side trunk panel off to get to the hydraulic pump.
You may not have any leaks because your hydraulic fluid reservoir is low.
If fluid is at the proper level then have someone press the top switch while you see if the hydraulic pump is working.
You should be able to hear it.

jeffjensen121

My apologies. I should have stated that the fluid is fine and the pump works. it raises and lowers the roll bars, I can hear it working when trying to lower the top. The top actually lifts just a smidge, and the hydraulics will push the top back into place when I push the button to close. Like I said, I get a recurring low voltage code. The dealership says I have a mild drain in the system, maybe an exposed wire somewhere. Just looking for ideas on where to start looking with my voltmeter.

RBYCC

You may be looking at several different issues.

The reason why I asked that you raise and hold the RPM to 2000+ and try to lower the roof is because this should increase the voltage output of the alternator to 13.5+.

For the dealer to read a low voltage code without testing the alternator does nothing for you.

Your top lowering electric/hydraulic circuitry appears to initiate but not complete the process.
This may be a result of the top control module not functioning properly.

Purchase an inexpensive digital voltmeter that you plug into your cigarette lighter.

http://www.ebay.com/itm/Mini-12V-24V-LED-Display-Digital-Car-Volt-Meter-Vehicle-Voltage-Gauge-/190836328475?pt=LH_DefaultDomain_0&hash=item2c6ebb481b
This will give you a real time indicator of your battery and alternator output.
When you first turn your key on do all the warning lights on the dash cluster illuminate?
If so you are confirming that the alternator exciter circuit is functioning.
Turn your key on and you should read 12.5+/-, start the car and you should read 13.7+/-.
A bad voltage regulator or alternator will read under 12 on start but may jump to 13.7 if you rev the engine.

Typical nuisance current drain on W124's is from the Becker Security System Module.
Easier to disconnect then repair/replace.

Ed A.

jeffjensen121

Ed A,

Thanks for the info. A friend of a friend stopped by, a Porsche mechanic. We started tracing power right at the pump. Power works in both directions, but pump only works one direction, which is closing. So my next questions would be 1) replace pump? 2) replace relay on pump 1st?. 3) will a pump from an sl320 work in this instance?

Again, thanks for the help

RBYCC

Jeff

Before you do anything read through this very long thread:

http://www.benzworld.org/forums/w124...on-1994-a.html

It may or not help you with your current problem, but is a "keeper" for any cab owner.

The logic is complex on the top and involves quite a few elements.

Not sure if the pump only works in one direction and a valve operation creates the up-down flow of hydraulic fluid.

I'm trying to find the hydraulic diagram.

Ed A.

jeffjensen121

Ed A,

Thank you. I had part of this post before, but not all of it. Top Hydraulics is located about 2 hours from me. I will give them a shout later today and see what to do next. At the least, I now have an excuse to cruise down the coast.

RBYCC

I'm on the "other" coast..highest elevation would be a sand dune...
Not as great a cruise as your coast !!!