89 gmc 2500 speedometer

i have an 89 gmc k2500 and the speedometer doesnot work if it is over 60 degrees outside. it will work for me in the morning but in the afternoon it doesn't it just stays at 0. when this happens the oil pressure seems to be low around 15-20 psi. it has a 5.7 tbi and automatic transmision. anyone have an idea what going on?

Hmm. I just had to fix my 88 s15 speedo and I didn't notice anything that would be affected by the temp outside. There has to be another factor causing it not to work. I found a whole gauge panel at a junkyard for $45 and I swapped it out and it now works great.

I have a 1988 1500 chevy parts truck, if you find out what it is let me know and I will see if the part is the same on mine. If it is you can have the part you just pay for shipping.

it was just a loose wire on the speed sensor