lfe132

Hello Everyone,
I have an 84 Carrera.
Can the Speed and Reference Sensor be replaced without removing the engine and trans?
Let me know, thanks.
Larry

Amber Gramps

Larry, are you on page 200-5 in the bentley? Turn the page over and look at the second diagram. When I thought I was replacing the "Idle Position Switch" I actually replaced the "Full Throtle Switch". So, don't ever listen to me again........

lfe132

Doug, on pg 200-5 of Bentley, it clearly shows the sensors with the trans separated from the engine, but I'm in total denial. LOL

old man neri

I don't think you have to. I would do a search on Pelican. Also, rumour has it that one can use a BMW part for the sensor that is identical but less than half the price.

lfe132

Old man. that would be great but how do i cross a P-car sensor with a beemer sensor. LOL hard to imagine a beemer sensor cheaper.

old man neri

Apparently they are the same bosch part. The only difference is the BMW part has a longer wire lead. Like I said, search it out to make sure and see comments about people who have done it. I have no personal experience with this.

Cheers!
-matt

3.2SLANTNOSE

Yep, do a search about the BMW Bosch Reference sensors. Many here say that they work without problems, and they are about 1/2 of the cost of the Porsche # parts. You do not have to drop your engine or anything else to change the sensors. Just jack up the rear, place your jackstands, so you can roll under towards the front of the car. You will see the holder that holds the two reference sensors to the bell-crank housing. If you can remove your old sensors from the holder, slip in the new ones and route your pigtails. If you can't remove the old one from the holder, loosen the bolt(s) that hold the sensor holder to the bell-crank housing, then take to you work bench and replace them. If you do it this way, you will have to set the air gap using the correct sensor, with a washer temporarily glued to the bottom of the sensor. If you have the Bentley book handy, you should have no problems. I think the washer thickness is 0.8mm. I do not have the book with me right now, so I can't say for sure what the thickness is for the washer. Good luck!! Tony.

Amber Gramps

Thanks Tony,

Larry, Why are you doing this anyway? What trouble are you having. When I did my head temp sensor last week I noticed my sensor "pigtails" were horribly cracked and falling apart. The braided lines inside the cord was exposed and the plastic was just falling off. Yikes, is this my next roject?

g-50cab

You can - but it isn't easy -

lfe132

Doug,
I've been having problems with my car. It'll start up, run for a few seconds and then die. I've checked all the threads on this, have done a bunch of trouble shooting. When it came time to check the ref and speed sensors I get NO reading for the high resistance test. And it seems that someone on the Pelican side has had the same problem as I, and was able to resolve the problem by replacing the 2 sensor.
Getting a little frustrated.....

PorscheMD

I used to check the sensors with a volt meter set on millivolts. If you get any reading at all while cranking the car then they are working. Obviously the more acurate way is to test the with a scope.

rnln

seeing a friend replacing them, I can tell that they are definitely not easy. The hardest part is to get the sensor off the housing. He finally had to take the housing off to replace them. Another problem came was that when you put them all back, how do you know how much to adjust them so they are xx mm gap to the fly wheel? At the end, he had to tow the car to the shop. 2 days later, he found out that the sensors were bad, maybe because he twisted them while pushing them back into the housing. it's hard not to twist them.

DRACO A5OG

What ever you do do not twist the new ones on, it will break it. It is liken to a light bulb, if you twist to install, it will break the filaments inside and make then useless.

BTW, I am the friend that towed it to the shop. Did not save a penny on this DIY in fact cost me $700, DOH

The wrench did not remove the engine and infact placed the new sensors on the bracket and guaged it and Voila, she started. Boy Did I feel like a Freakin Retard.

Lorenfb

"If you get any reading at all while cranking the car then they are working."

Actually not really correct. There's a minium AC voltage level for each:

1. speed - ~ 2.0 VAC
2. ref - ~ 100mVAC

Obviously, both are measured while cranking. Each should
measure about 1000 ohms.

3.2SLANTNOSE

Loren, I was hoping that you would give some info on this. Thanks.

Doug and the rest, I have not ever replaced the sensors on the 915/3.2 engines, without removing the holder. I have found that it is much easier for me, being done this way:

MAKE SURE TO MARK BOTH SIDES AT THE PLUG CONNECTORS.(DG or BG, explained later)
Also mark the new sensor leads so you know which one is which, because the sensors are identical parts.
Remove the old sensor connection plugs from the plug connectors and route them back towards the holder area.
Raise the rear of the car and then support with stands.
You will have some odds and ends to get through where they pass through the engine tin in the same area as the CHT lead.
With the rear end up in the air, supported on stands, slide under, loosen the bolt(s) that secure the holder to the bell-crank housing.
Remove the holder with the old sensors and go to your workbench and vice.
Apply a crud loosening agent(I prefer, PB-BLASTER for this) to the sensor retaining bolts and at both ends of the old sensors, where they sit in the holder.
Remove the retainer bolts.
Remove the old sensors(if you are replacing with new, you can use the twist a little back and forth, then pull out method, you won't be using them again. If you are to reuse them for whatever reason, you do not want to do the twisting bit, you will have to be more patient and remove carefully, so you don't destroy the sensors)
Now that you have the old sensors out, you need to clean the holder where the new sensors will be installed.(I have found that a large caliber firearm, bore brush works great with a little PB applied for lube, also make sure to clean the rest of the mounting threads and such)
To reset the air gap, you will need to glue a 0.8mm to the bottom of one of the sensors(make sure the bottom is FLAT they sometime get deformed from the years of heat and tend to bulge out instead of being FLAT)
One tiny dab of super glue on the clean bottom of the sensor is all that is needed to hold the 0.8mm washer to the bottom. (If your available "gap set" sensor bodies are all bulged, you can use one of the new ones, just be careful when removing the washer and glue with acetone or nail polish remover.)

As this is from memory, I can't remember which sensor gets the air-gap setting washer.

Once you have the new sensors secured in the holder, install the holder loosely to the bell-crank housing.(the sensor without the washer, is adjusted by the other sensor's effect on the holder adjustment, it actually is set and adjusted properly, when secured to the holder in its proper placement)
Once the sensor bottoms out on the ring gear/flywheel, tighten the bolts on the holder to secure it at that adjustment level.
Remove the sensor with the gap washer.
Remove the gap washer and glue residue and reinstall in holder.
Make sure that a fasteners are torqued to spec. Route the wires back through the grommet and then connect to the proper connector
DG - DREHZAL-GEBER - Speed Generator
BG - BEZUGSMARKEN-GEBER - Ref Mark Generator
Make sure everything is returned to its proper place.
Now you can attempt to start.
If all is well and engine starts and runs fine, GREAT!!
Now you can do whatever else you want to do while the rear is up it the air.
See it really is simple, you DO NOT HAVE TO DROP ENGINE.
With the aid of a Bentley Manual you should not have any problems.

Hopefully I made this easily understood(and not forgot any steps) and simple enough to take the worries out of the ref/speed sensors replacements. Good luck!! Tony.
ps Doug, how are things going. Take care friend, Tony.