Overdrive relay on 740T

volvo_user · Post by **volvo_user** » 02 Jan 2005, 22:21

I have a 1988 740Turbo. Recently the overdrive indicator comes on randomly. When it came on, my car dropped into 3rd gear (I think) and slows down. This is no good at all when I am driving at high way speed around 100 -120 KM/hr. I have checked the overdrive switch on the handle of the automatic transmission stick. It seems ok. I can have overdrive turned on by pushing it once and turned off by pushing it once more. Any idea what I should be looking for ? Should I go ahead with replacing the overdrive relay?

LaRy · Post by **LaRy** » 03 Jan 2005, 03:19

The fact that the function is working OK when pushing the button is an indication of a good working relay. The relay is on and off including correct information with the arrow, that is good. To me this sounds like bad insulation on the wire from the push button to the relay. Have you been looking at the flexible wire between the handle and the floor? That wire is moving every time you change position of the handle. I think you will find the problem there. Look for connection to ground.

TAFinley · Post by **TAFinley** » 04 Jan 2005, 14:47

You can check my posts on this site about the 240/740 overdrive relay/wiring/solenoid, but I don't think there is a problem with any of these systems based on your description of the problem.

IMHO, LaRy is this site's resident electrical expert. From the symptoms you describe, I believe LaRy's answer to be correct. Start looking at the electrical wiring between the switch on the shifter and the relay before you do anything else. Your symptoms do not indicate a faulty relay, faulty solenoid, or a short in the wiring between the relay and the solenoid.