check engine oil light

I just got an 88 b2200 and the check oil light comes on when im driving and press the clutch in and brake. when i accelerate it goes off again, i checked the oil level of the vehicle and its fine, i have no idea on what to do , If there is anyone that can help me out i'd greatly appreciate it. Thanks

I have a 93 and am having similar problems. I'm also having it looked at tomorrow. I'll let you know what's up.

Bad oil pressure sending switch. BJ