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Marty
Marty, Bosch Certified Technician
Category: Transmissions
Satisfied Customers: 53162
Experience:  Bosch certified master technician. Over 35 years experience.
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1990 SL 300-24 WONT SHIFT INTO OVERDRIVE

Customer Question

1990 SL 300-24 WONT SHIFT INTO OVERDRIVE
Submitted: 2 months ago.
Category: Transmissions
Expert:  Marty replied 2 months ago.

Hi Randy, my name is***** you tell me what has been checked or replaced so far to repair this problem?

Customer: replied 2 months ago.
WHEN I BOUGHT THE CAR ABOUT 1 YEAR AGO THE OVERDRIVE WAS WORKING FOR A SHORT TIME . THE SRS LIGHT IS ON AND STAYS ON .I HAVE TAKEN THE SHIFTING TOWER APART TO CHECK THE OVERDRIVE SWITCH IT SEEMED OK . THAT IS ABOUT ALL THAT HAS BEEN DONE A MONTH OR SO AGO I DID CHANG OUT THE TRANS OIL AND FILTER
Expert:  Marty replied 2 months ago.

The first thing you should do is check the fuses in the top of the overvoltage protection relay. The relay is under the hood at the right rear. I've attached a picture below. The relay is tucked behind the tall relay with the knob on top. Let me know what you find.

Customer: replied 2 months ago.
I HAVE CHECKED THE FUSE AND IT IS GOOD
Customer: replied 2 months ago.
i have already checked the fuse and it looks ok.
Expert:  Marty replied 2 months ago.

Sorry for the wait I had a busy day at the shop and could not reply. Next I would test the voltage at the overdrive solenoid on the transmission. Measure the voltage at the solenoid with the key on engine running. If you have no voltage to the solenoid you have a fault with the control unit or the wiring. If you do have voltage to the solenoid you will need to do a voltage test at the solenoid while road testing the car to see if the voltage changes as you get to cruising speed.