Probably should have put this here rather then SL thread, sorry.

I have a '90 129 that won't shift into 5th gear. I took it to Mercedes and had it checked out and they spent a number of hours on it and came up with a bad HSG mod.

Because I have a repair shop and we're over 2 hours away from the dealer I ordered and installed new HSG with no change. This problem has been going on for a few years now so we reinstalled the original HSG and found a code 9, road tested the car with this controler and there was a 3-5 shift skipping 4th.

While we working on this car in the past, when the new HGS controler was installed we found a bad connection on the trans overload protection switch so I figured the old controler still had that code in it so I cleared the codes in all the mods and road tested.

Back to square one, no 5th gear and no codes in any of the mods. I don't understand why it doesn't set a code when it's not shifting into 5th, Anyone have any ideas?

Thanks,

Ron

What else was changed, done to solve this problem? Do you no 5th or no 4th

Nothing has been replaced other then the HGS mod. I dropped the pan and cleaned the sol. but didn't really find anything there. Repaired a connection on the trans overload switch. Checked the over voltage relay, this one has a fuse in it and it has never been blown. Checked the function of the switch on the shifter and that is working properly.

I made a pulse tester and that is what I'm using to get the codes. I can access the MAS, EZL both of which have a list of codes in alldata but I couldn't find a list on the HGS mod. I used pin 14 for the MAS, 8 I think for the EZL and 13 for the HGS. The code 9 I pulled from the HGS I thought was the trans overload switch but I'm not sure of that because I couldn't find an actual list for the HGS.

Not that long ago when driving the car with the new HGS installed the car shifted perfectly for about 50 miles so this leeds me to believe that it is a wiring/connection issue rather then a transmission fault. I've checked the vac lines and found no problems.

My understanding of the system is that the controler looks for load, RPM's and the position of the shifter switch. All things being right it is suppose to shift into 5th.

I never knew the 90 SL had a 5th gear. My 95 only has 4.

__________________
95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

I thought the 5 speed (electronic shifting) debuted in model year 1995 on the R-129 series

Mine only has 4,,,,, but maybe should have 5. By God this thing may do 190 miles per hour if it ever hits 5th gear !!!

__________________
95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

Hi

Can you please e-mail the diagnostic pin chart , I have a problem with my 300SL 1992 .
Only first and the second gear works , won't shift into 3-4 or 5th gear and the speedometer doesn't work .
Thank you .
Peter
pkurek@cfl.rr.com