Cruise/Brake Light Switch Problem

[jaustinmd]

I've been trying to resurrect the cruise on my 82 911SC. (Just had the cruise module repaired by Kris Rose). I'm now down to one diagnostic problem (I "think"!):

The Bentley Manual diagnostic "Table c" for cruise troubleshooting says to "connect ohmmeter between terminal 6 (of cruise module harness connector) and ground." The results box says there is no fault if "Meter reads infinite ohms." If the "Meter reads 0 Ohms" then the "brake light switch is faulty."

Initially, I got a few tenths of an Ohm, (and certainly not infinite!), so I interpreted that as a "faulty brake light switch" although my brake lights (incandescent bulbs) seemed to be working OK except maybe required firm pressure before they came on (which I understand many complain of).

So, I went ahead and replaced the switches with quality, ATE brand switches. Much to my surprise, I'm still getting exactly the same ohmmeter results!

Is the Bentley Manual in error and has the ohmmeter results switched (pun intended! Ha!)? However, it does seem like the circuit would have to disconnected ("inifinte resistance") or my brake lights would be "on" all the time, which they are not!

One additional fact that may be significant - all my turn signals, side marker lamps, parking lights, etc. are LED. The only incandescent bulbs are the 1157's on the brake lights. Is there any inter-connection in the circuits so that these other LED's could be affecting the brake circuit?

I hope someone can help with my confusion!

[porschenut]

The Bentley troubleshooting chart is incorrect, and this answer was already given to you 2 weeks ago in the thread you started (did you forget?):

Brake Light Switch Defective?

[jaustinmd]

Originally Posted by porschenut

The Bentley troubleshooting chart is incorrect, and this answer was already given to you 2 weeks ago in the thread you started (did you forget?):

Brake Light Switch Defective?

The Bentley "glaring error" discussed in that thread was concerning the clutch switch and not the brake switch.

However, there is one sentence in that thread that says "11.8v is supplied to pin 6 when the brakes are applied." Am I to infer that the Bentley Ohmmeter test of pin 6 is to be disregarded and instead look for 11.8v on pin 6 with ignition on and brakes applied (which happens to be the next Bentley diagnostic test on the table). My initial check was good on that next test, but I haven't repeated it after the new switches (but I will!)!

I guess what I'm really asking is that if pin 6 gets 11.8v (Bentley says "battery voltage") with the brakes on, can one simply disregard the ohmmeter test of pin 6?

(BTW, the clutch switch circuit checked out OK by the testing method suggested in the thread.)