Questions for techs on my SL, please read>> - PeachParts Mercedes-Benz Forum

Eli (NJ) · #1 05-20-2002, 01:59 PM

Currently i have two problems and need help solving them.

1. My convertible top will not open with the button, it only flashes when i try to activate it. It is not lit with car running and will allow me to close the top. All the switches appear to be closed and the alarm doen't sound when in drive. I noticed recently that the ABS light came on before i tried to operate the top. Are these related? Does the car not know it's in park for the top to open?

2. My auxilliary fans never come on in low speed. Only in high speed and when my temp reaches about 115*C, or with the AC pressure. Is this normal for the SL, or is my temp sensor or switch shot?

Thanks in advance for all responses, as you can imagine both of these issues are frustrating in the warm weather now. Eli.

Eli (NJ) · #2 05-21-2002, 05:15 PM

Any suggestions would be welcome here.

mbdoc · #3 05-21-2002, 05:59 PM

The aux fans should come on low speed as soon as the A/C is turned on. Then go to high speed when the engine reaches 107C OR the A/C pressure reaches 295psi.

If you have a RED pressure switch in the drier then the fans will go to high speed when the A/C pressure reaches 220psi.

Soft top problems aren't DIYer, even many repair shops don't have the correct diagnostic equiptment to diagnose this system.

DALE DORIA · #4 05-21-2002, 06:44 PM

Agree.......this is a dealer problem to solve.......Good Luck and keep us posted!!

AJG382 · #5 05-21-2002, 07:16 PM

Eli;
I had the same problems with my top last year and the ABS indicator also kept coming on as well. The dealer solve this by replacing the OVP relay.

Eli (NJ) · #6 05-22-2002, 05:27 PM

M.B. DOC, where's the temp/turn-on switch for the fans, in low speed? I've checked the pressure switch, it's fine, they run in high speed.

AJG382, do you know where the OVP relay is and what it costs?

Thanks alot for your responses, the search results aren't specific enough for R129's. Eli.

bobterry99 · #7 05-23-2002, 12:06 AM

Troubleshooting electrical problems in the soft top control system is surprisingly easy. No special tools are required. You may need a simple multimeter for checking some electrical circuits after performing preliminary diagnostics.

The switch flashing means the controller has a fault stored in its memory. Reading stored codes is a logical starting point for diagnosing your problem. I recommend that you: (1) read all codes and write them down, (2) erase all codes you possibly can and write down any that will not erase, (3) try to open your top, then (4) if still no luck, read codes once again and report all your findings in a follow-up post.

The controller outputs a code by issuing a series of electrical pulses. You can view these pulses by watching the indicator lamp in the soft top switch blink. To ouptut a code of "12" for instance, the lamp would blink twelve times.

To trigger a code output, you short socket 10 of the diagnostic connector to socket 1 or any other convenient chassis ground for two to four seconds. While the short is connected the lamp should be on. The instant the short is removed the lamp will go out and after a brief delay will begin to slowly blink-out a code.

The diagnostic connector is located by the left front shock mount on the 2nd fire wall in the passenger compartment. It is rectangular and has a plastic cover.

A code of "1" indicates no faults and no hard top in place, while a code of "20" indicates no faults and the hard top is assumed to be on the car. Other codes identify a specific problem such as a limit switch. The codes that you find dictate what component of the system you troubleshoot next.

Repeat the read procedure until you have all of the codes. You implicitly know you have them when the sequence of codes begins to repeat.

You erase a code by reading it, waiting three seconds, and then shorting socket 10 to ground for six to eight seconds. With early versions of the soft top controller (up to v. 7.6) you must read a code twice before you can erase it. Naturally, this constraint is met if all of the codes are first read before any are erased.

I should mention that an LED may be wired between socket 10 and ground to read codes. It will blink out of phase with the lamp in the switch -- that is, when the lamp is on the LED is off.

Finally, I'll take a SWAG at what you will find your problem to be. There is a switch with an adjustable plunger that makes when the top lowers into its compartment. Yours might be stuck closed. I have a hunch the controller only considers this input during an opening sequence and ignores it for closing. All other inputs very definitely must be functioning to successfully perform a complete closing sequence.

mbdoc · #8 05-23-2002, 08:21 AM

Again the low speed of the aux fans is controlled by turning on the A/C compressor. The pushbutton control panel sends a signal to a relay for the low speed fan control. From there it goes to a "ballast" resistor under the left headlight & then to the fans.

Eli (NJ) · #9 05-23-2002, 04:37 PM

Bobterry, thanks for the info, but where is this diagnostics connector located? what about the OVP relay? Eli.

AJG382 · #10 05-23-2002, 06:29 PM

Eli,

On my car it is on the passenger side by the firewall. It cost me about $80 US at the dealer so I assume that the part is not very expensive.

bobterry99 · #11 05-23-2002, 06:32 PM

It is on the passenger side of your car at the 2nd firewall as shown below (with cover removed).

Eli (NJ) · #12 05-28-2002, 01:26 AM

Here's an update for you guys. I solved the convertible top problem by replacing the fuse on a relay (OVP relay I assume), and thankfully my ABS light went off. What a relief, no trip to the dealer or mortgage needed. The fuse probably blew when I had to jump the car a few weeks ago.

Now I just have to make the car run cooler, I hate to see temps of 115*C regularly on warm days, no matter what Mercedes says about that being normal. No engine should run this hot.

Thanks for everyone's help and I hope you all had a good holiday weekend. Eli.

#13 05-04-2003, 07:55 AM

hi eli!
I have a similar problem and needed to know where the OVP relay is located and if possible the part no. as well

Thanks

Eli (NJ) · #14 05-04-2003, 02:36 PM

The relay is located on the side of the passenger shock tower in the engine compartmernt. It is under a small cover and has a fuse on top of it. Not too hard to find if you're in that area.

#15 05-05-2003, 10:54 AM

does it have a red fuse , sorry fr sounding stupid but the only thing close to it is undr a big cover on passenger side and is cylindrical.