68 Temp Senders / Wiring / Timing covers

[Glen356]

Hello everybody. Mine name is Glen. I'm the friend of GregD who recently purchased a 68 911 and have been having some issues that he has been asking questions on. As I work through them I run into more questions. But my buddy Greg came up with some lame excuse that it would be easier if I joined the forum and asked the questions directly (personally I just think he's lazy.

Ok, based on previous info provided regarding the temp sender location. I have taken a old VDO sender from a 912 engine I have (been told its the same since I have 912 style gauges) and replaced the sender (A Beru) that was working the gauge. I went from showing a car that was nearly over heating after 20 mintues to a car running at hat I consider normal range after 25 miles. Now again with info provided. It was confirmed that the sender on right is the correct location not the operational one on the left. The VDO 912 sender in that possition does not seem to be working. So I moved the 912 sender from the left hand hole and installed in correct location on the right. I then started tracking wires.

This is what I found / did. Both senders are connected to green with black wires (believed to be correct). I tracked the right hand sender wire to the back of the engine compartment where it connects with push connector to a green with red wire that comes up between the body and the engine from the starter area (it IS s a wire that comed out of the factory harness). I then tracked that green with red wire to the gauge area where it has been zip tied and is not connected. So this right hand sender has been a dummy. I then took the left hand sender wire and wrapped it around the rear of the engine compartment and attached it to the green with black wire that went to the right hand sender. The wires are perfect length, and this connection looks like it was originally this way. I then took the original left hand Beru sender and put it back in the left hand hole just to fill the hole in the timing cover. This was done at 1am last night. All seems to work but I have not had a chance to test drive to check temps.

Now I Currently have three quesitons regarding this particular issue.
#1 What is the green and red wire for?. It comes out of the harness near the starter and and ends at the gauges.
#2 Based on info, it sounds like the timing cover is off of an SC (as that is the only one with a hole where this left hand sender went). However per the one book GregD loaned me (more books are coming rest assured), it says that the covers are universal from 69 thru 83. But mine is a matching number 68 with a build date of May 68. Would an SC cover still fit my car? If not, then what do I have here?
#3 Why would somebody do this? It not like somebody amaturishly ran a wire and re-routed. They used the correct color wires where visible etc... I get the feeling this was done professionally. I don't get the point! Any ideas?

Thank
Glen

[Greg D.]

Lazy friend here: I should recap because I've asked questions on 2 threads before Glen got his butt in gear and posted all by himself ;-) The car is a 68 "normal" with what seem to be 912 temp gauges, no oil pressure gauges, no oil level.
The temp gauge was showing the car to be running very hot, 250-280 hot. It was also low 1.5 qts, and the left side heater vent is blocked off. He since did a bunch of things, checked timing, shot an IR gun around... It seems that the car has an SC chain cover on the left side with a provision for a sensor which is NOT the oil temp sensor, and that was what the car was reading !!! So he's now trying to get the correct 68 sensor (right side) replaced, connected to the temps gauge, and working accurately.

Now back to the original programming..

PS: I understand base 68s came with those limited 912 gauges, wouldn't you recommend upgrading to normal 911 gauges ? Seems to me not having oil pressure / oil tank level indication on a flat 6 is kinda dangerous, authenticity be damned !

[edmayo]

The green / red wire is for the oil pressure gauge which was mounted back by the crankcase breather. You stated your car doesn't have a numerical oil gauge, therefore that wire isn't used. And yes, the oil temp wire did route around the rear of the engine as you now have it. If you have a mag case the SC cover fits, I believe mag started during end of 68 production.

[304065]

Glen,

First, WELCOME to the forum.

Do you have the original owner's manual for your car? In the back you will find a color wiring diagram. Because this material is in the public domain, fair use allows its reproduction here, copyright is held by Porsche KG (SE these days, part of Volkswagen group!) The diagram is called "L57." http://members.rennlist.org/911pcars/L57.pdf Download this and study it carefully.

Now look at the diagram and find item 47, over to the right. That is the oil temperature sender. Note the green wire with black stripe.

And in the same area, item 49. That is the oil pressure sender. Green wire with red stripe. Even though your car didn't have an oil pressure SENDER for the gauge, it has an oil pressure SWITCH which triggers the warning lamp in the dash. That is what the green/red is doing in your harness. The reason it's so short is that it's intended to connect to the switch which is screwed vertically into an adapter at the top of the engine next to the thermostat.

Now, it's a fact that all the harnesses are the same, 911/912. Even though your normal has "normal" gauges, the wires are still present, they are just capped off with some thick rubber tubing to insulate them from the chassis, and taped up with cloth tape by the Factory. The Factory didn't use zip-ties, ever. So the green/red goes to the oil pressure warning lamp bulb holder on your temperature gauge.

The extra green/black and the SC chain box cover don't belong. In 1968 the Factory got tired of oil leaks and increased the number of studs on the chain box cover to the "modern" number. Hence an SC chain box cover fits. You don't say whether you have a magnesium or aluminum cased motor-- if you have a Mag chainbox, it's easy enough to find a mag cover. The 68 had an airpump drive on that cover, which is why somebody replaced it with the modern part, but they were mistaken in the effort to pick up oil temperature there. Turkeys abound, half the fun is identifying what's supposed to be original and the other half of the fun is putting it back to original.

All right, a note about senders. Can you please post a detailed macro photo of your Beru sender. As I posted in the other thread started by Greg, there are two versions of the temp sender-- one with a long brass tube that sticks into the hole by the engine number, the other with a short tube. The long one is the original, and it should have some numbers and a date code stamped into it, that's what we're trying to capture with the photograph.

If there is a mismatch between the sender and the gauge you will not have accurate temperature readings. The solution is to either use the right sender (expensive and probably NLA) or change the gauge to work with the short $15 sender.

If you wanted, it would be quite simple to source a replacement "S" gauge that has both temperature and pressure, get a VDO 0-10 bar M10x1.0 oil pressure sender for the green/red, and a modern temperature sender for the green/black, and then have the gauge modified to work with the modern temp sender. This would assure you that your readings are accurate as far as it goes.

I'm concerned about the high temperatures-- I would check the ignition timing, and do a leakdown test, to investigate fully the condition of the engine. When a SWB 2,0 starts running hot it's indicative of a bigger systemic problem, which is easy enough to check out. You want to be confident when enjoying your car.

Good luck! Let us know if you have questions.