My cruise on the 84 work intermittenly......It will only work when first started on a cold engine. It will work all day long if I don't shut the car off. After I shut the car off it will not work again for several hours. What's Up?

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81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project