Ive searched the site and couldnt find the answer.

I have a 1987 Toyota truck, 4 cyl, 22R, 2wd, base, each time I use the truck for the first time of the day or after it had cooled down the overdrive will work (will work with and without the OD button), once in overdrive and slow down below overdrive speed the overdrive will not work thereafter only after the vehicle has cooled down.

I have changed the thermostat with no luck, Im suspecting the coolant temperature switch. Can someone tell me the process on testing the switch? Also, am I able to bypass this switch? If so, how and in doing so, will see a change in shift pattern or will I need to manual shift into (4th gear) overdrive?

Great site, very informative!

 

I did some testing on my existing temperature switch with the following results, let me know if this normal or not.

I placed the switch into a pot with water and temp probe and noted down the ohms during increase of temp.

Atmospheric temp no water no body temp 80 d. .5 hms

Temp increase

150 d. 0
175 d. 0
200 d. 0
220 d 0

Cooling down
220-125 d 0
110 d 1.2
100 d .4

What do you think?