I was driving my 86 Carerra harder than usual on the highway today. Revving the engine in 4th, downshifting to 3rd, revving up again etc. Very spirited compared to the way I usually drive. Anyway, after winding it up to a speed I won't mention, and exiting the highway, at the end of the ramp I noticed my oil light came on when my engine was at idle (800 RPM or so). I immediately shut the engine off and checked the oil level, and its was full of clean 20/50 GTX. I started it up again, and checked my druck pressure and it seemed normal. I only had a mile or so to go so I took it easy and went home.
I let it sit for a half hour or so and started it up again and the light didn't come on again.
I then took it for another longer highway drive and noticed the following once I exited the highway: my oil pressure warning light, brake warning light and brake pad warning light ALL come on when my RPMS are below 1000. As soon as my revs go up, the lights go off.
Did I mess something up with the alternator?

 

I would think your voltage regulator is now shot. Don't blame yourself, they just do that after 10-12+years.
Hihgher revs tend to make it overshoot +12VDC to as high as +14 or more.
Drive it again, this time with the high beams on and the stereo playing. See if it happens again. If so, then I would certainly get it to my mechanic to check the alternator. Come to think of it, I would take it to him anyway, becasue if it concerned me at all, I would want it to be checked out instead of prolonging it, or possibly just making it worse, unsafe or unreliable.
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I was having an electical 'anomaly' the other day as well, and another user suggested I replace the voltage regulator. On an 86 its an easily replaceable 'internal' one. $60.

http://www.pap-parts.com/prodinfo.as...603%20913%2001

Hmmmmmm....it always worrys me when someone tells me a repair is going to be easy....

 

So what was involved in replacing it?
Did you have to pull the alternator?
Does it come with instructions?
I'll order one tomorrow.
Thanks.

 

I'm not familiar with the newer 911's but you say that you shut the engine off and immediately checked the oil level. Are the newer ones different than older 911's in that you check the level with the engine off?

 

The oil has to be checked with engine idling, on a level surface, at operating temperature.

 

I wasn't terribly alarmed/concerned about your oil level as you didn't mention any smoke, loss of power or other such catastrophic warning signs.
I just figured that the voltage went high enough to send a few false signals to some indicator lights.
Again, you can check the voltage at the battery at idle to determine if it is 12VDC or more.
At higher RPM, the output of the alternator will increase to 14 or so if the regulator is bad.
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I realize the correct method of checking oil, but obviously if the dipstick was dry the the engine was dry, I'd have a problem. As it was, I was at the "add" line with the engine off.
I didn't want to start it if I had no oil.

 

I drove it again after adding two shims to the fan belt and snugging it up a bit. The lights came on again, so I turned on every accessory (stereo w/amp, hi-beams, heated mirrors, heater blower, and power windows) and had the same problem at idle.
What now?
I haven't found a mechanic in town yet. (London Ontario).
Any ideas? (Regulator or Alternator)

 

What you have are the classic symptoms of a failing/failed oil pressure switch.

 

Hi Mark, Thats great if thats what it is, but just curious, why would it cause the brake warning light and brake pad warning light to come on also?

If this is the item I need, I'm getting off real easy.
http://www.pap-parts.com/prodinfo.as...606%20230%2000

 

That's the culprit!

If you look at the wiring diagram, you'll see that the lead from that switch goes to the O.P. idiot light and a solid-state device which drives that light cluster. I've never seen an official explanation of the reason, but I suspect it's to ensure that if there's a sudden loss of O.P., one of the lights will catch the attention of the driver or passenger.

 

Nice little operation they have. I ordered my switch via the toll free # in a matter of minutes.
Thanks Mark

 

It's a 'fun' job to access & replace. You'll probably want to lower the rear of your engine & remove the intake plenum. best of luck with it.

BTW - conventional wisdom says you should also replace the o-ring on the engine t-stat, just to the right of the pressure switch, while you're in there.

 

This explains something. My oil level indicator and pressure gauge have bounced around a bit & I've noticed the brake sensor light came on 2 different times (not too long after new sensors & a complete brake job).
I quizzed my mechanic, but neither of us had an answer from my description of the events.
I'll assume this could be the problem because if the brake sensors were faulty, etc. the light would either come on repeatedly or stay illuminated, correct?
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