84 P-Type Strange Dash Behavior

[68droptop]

Need some council. My 84 5MGE, manual trans, analog dash; speedometer quit working a few weeks ago, and strangely the cruise control went out at the exact same time. I thought the speedo cable was bad, changed it but no different. This week the car seems to loose some electrical power in the system. When I get on the gas sometimes the fan on the A/C and the lights pull down until I shift. Also the tach will jump around and give odd readings. Has anyone dealt with something like this and I am looking for suggestions. Thanks for your time and input.

[menesesjesse]

Check you grounds. They are all over on the inside. They need to be tight and clean

[68droptop]

Thanks I will give it a try.

[lechner]

Also might pull into your local auto parts chain and have them check your alternator output while running. The cruise control has to know how fast you are going to work. Detach the speedo cable at the gauge, pull it out where you can see, and check that it spins while you are driving.