Mike C.

On the early cars the speedo and cruise control are referenced to the driver's side wheel turning (US cars). It's obvious enough that the speedo cable engages the bearing cap to turn the cable at wheel rpm. What isn't obvious is where the pulse-hall sensor is located for the cruise control. I've searched through the shop manual pretty thoroughly and it just doesn't mention where the bugger lives. Since I have pulled apart the CC brain and re-soldered all of the joints and otherwise checked out all other components the CC had been working well for several months. The colder weather seems to be aggravating the old intermittent problems. Sometimes it won't work at all, sometimes it will turn on but then has difficulty maintaining a set speed and eventually shuts itself off. Although the PH sensor tests out OK in the garage when turning the wheel slowly, I'm curious if it may be the intermittent culprit.

IXLOR8

I might have the same problem as you. 1984 Porsche 944

1) My power sunroof does not lock when the key is in the ignition. It might have something to do with the speed sensor in the driverside front wheel. The manual makes mention about 5mph.

2) The cruise control does not operate.

Could this wheel senor be the cause of both problems?

I will search manuals for some more info.

Mike C.

I did forget about that. I'll have to give it a try...

jpk

Hall sensor for the cruise is on the back of the speedometer. green and brown wire pair going straight over to the tach.

It feeds a signal into the tach for the fuel economy guage, then backfeeds the cruise control signal through the DME.

If your fuel economy guage shows reasonable readings, the hall sensor is good. If the guage shows very low fuel economy (swings to almost zero with even a slight throttle) then the hall sensor isn't working right.

taworden

So on the early cars the fuel economy gauge should not swing to zero on slight throttle? Is there a way to test the hall sensor for correct readings?

Mike C.

Thanks John. I wonder why they just didn't run the CC off the tachometer signal itself? I've seen other cruise systems that do just that....

Mike C.

The Hall sensor is tested, according to the FSM, by unplugging the cruise brain and measuring voltage on the connector between pins 11 and 12 (going by memory here) which should read from 1 V to 6 V as the driver's front wheel is rotated. It should do this 4 times per wheel revolution.