1989 740gl Overdrive problem

Sep 15th, 2002, 21:37

I appear to have a intermittant problem on my auto box 116,000mls. The overdrive only works occasionally, the dash light will stay on for days without any overdrive engagement.I can then turn the ignition on, the dash light goes out, over drive works fine for that journey. The next time I start the car, no overdrive. I have checked the button on the gear lever and that appears to work OK.

sheerwater · Sep 16th, 2002, 18:30

Not totally conversant with the 700 overdrive but is there a relay? I dont think that the button on the gearstick is a direct on/off switch.
I think that somewhere there is a relay which kicks in when you select o/d then kicks out when you change down a gear. If this is the case there must be a further switch operated by the gearstick similar to the reverse light switch. If so its worth checking the connections underneath for corrosion. Cheers Nigel

Sep 16th, 2002, 19:14

Thanks for reply.
Not sure if there is a relay, I will have a look. The Haynes manual is of no use whatsoever, it refers to the gearstick button and little else. Only owned the car for a week, not familiar with autos. Any idea how the overdrive works, is there a solenoid that could be sticking or somthing similar.

Peter Milnes · Sep 16th, 2002, 23:19

The overdrive relay is the rightmost one on the second row of relays behind the fuses at the bottom of the centre console (remove ashtray for access). As the lamp and the overdrive solenoid are fed from the relay contacts, then if the lamp is on then the solenoid is engaged and the overdrive is off. It may be that the relay is loose in it's holder but it is far more likely to be in need of resoldering of it's internal connections or replacement with known good one or new one.

All the best, Peter.

Sep 29th, 2002, 11:54

GS Thanks Peter, I have found the relay,will have a go at soldering connections.
I now have a more annoying problem, which likely to fairly simple to solve if you know where to look.
After a short journey I try to start the car and it won't start. There is no spark at the plug. If I leave it for 1/2 hour it starts. Sometimes it will start and then cut out after a few yards. This seems to happen mainly after the first short journey of the day. It appears to run ok once the engine has warmed up completely.
I have read in the manual, there is cold start unit, not sure what it looks like.
Thanks Graham

Sep 15th, 2002, 21:37	#1
gsauer Guest Location:	1989 740gl Overdrive problem I appear to have a intermittant problem on my auto box 116,000mls. The overdrive only works occasionally, the dash light will stay on for days without any overdrive engagement.I can then turn the ignition on, the dash light goes out, over drive works fine for that journey. The next time I start the car, no overdrive. I have checked the button on the gear lever and that appears to work OK.

Sep 16th, 2002, 18:30	#2
sheerwater Master Member Last Online: Feb 24th, 2019 17:59 Join Date: Dec 2001 Location: Northampton	RE: 1989 740gl Overdrive problem Not totally conversant with the 700 overdrive but is there a relay? I dont think that the button on the gearstick is a direct on/off switch. I think that somewhere there is a relay which kicks in when you select o/d then kicks out when you change down a gear. If this is the case there must be a further switch operated by the gearstick similar to the reverse light switch. If so its worth checking the connections underneath for corrosion. Cheers Nigel

Sep 16th, 2002, 19:14	#3
gsauer Guest Location:	RE: 1989 740gl Overdrive problem Thanks for reply. Not sure if there is a relay, I will have a look. The Haynes manual is of no use whatsoever, it refers to the gearstick button and little else. Only owned the car for a week, not familiar with autos. Any idea how the overdrive works, is there a solenoid that could be sticking or somthing similar.

Sep 16th, 2002, 23:19	#4
Peter Milnes Premier Member Last Online: Apr 10th, 2014 00:01 Join Date: Feb 2002 Location: Tonyrefail	RE: 1989 740gl Overdrive problem The overdrive relay is the rightmost one on the second row of relays behind the fuses at the bottom of the centre console (remove ashtray for access). As the lamp and the overdrive solenoid are fed from the relay contacts, then if the lamp is on then the solenoid is engaged and the overdrive is off. It may be that the relay is loose in it's holder but it is far more likely to be in need of resoldering of it's internal connections or replacement with known good one or new one. All the best, Peter.

Sep 29th, 2002, 11:54	#5
gsauer Guest Location:	RE: 1989 740gl Overdrive problem GS Thanks Peter, I have found the relay,will have a go at soldering connections. I now have a more annoying problem, which likely to fairly simple to solve if you know where to look. After a short journey I try to start the car and it won't start. There is no spark at the plug. If I leave it for 1/2 hour it starts. Sometimes it will start and then cut out after a few yards. This seems to happen mainly after the first short journey of the day. It appears to run ok once the engine has warmed up completely. I have read in the manual, there is cold start unit, not sure what it looks like. Thanks Graham

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