O/D no fourth gear

[The Swede]

I have problems with the automatic transmission, the fourth gear O/D will not work, it is a Toyota Van 88 US-model. There is a relay that switch the overdrive on/off and it is operated from the switch located at the gear level. This relay is working properly but as I understand it the relay is also operated by something else from the engine. As I understand it, if the engine is cold the relay will not switch to the fourth gear until the engine is warm. It must be a sensor that provide 12v to the relay but this is not working. For the moment I’ll have bypassed this and the O/D is working. Where is the sensor or what ever it is located that should provide currency to the relay? Or is it some other problems?

I purchased my Toyota Van 88 US-model when I was living in Japan then I brought it back with me to Sweden. My car is the one and only US-model existing in my country and it differs a lot from the Swedish models. The Toyota dealers and service personal are unable to answer my questions. I hope that anyone in this forum will be able to help me. Please excuse me for my poor English.

[fast repair]

i have the same problem. how did you bypass the system and made it work?
thanks

[The Swede]

I have solved the problem. There is a tempswitch which will hold the fourth gear untill the engine is warm enough. I replaced the temp s/w and the fourth gear is function as normal again.