Installing a combo gauge where there never was one

keitho64 · keitho64's Garage

I am looking to install the combo gauge for oil temp and pressure in my 69T. The existing gauge only has the oil temp gauge. The oil pressure is an idiot light. The new gauge has a provision for the idiot light for oil pressure, alternator and brake in addition to having the oil temp and pressure gauges. My questions are:

Do I need to change the sending unit for the oil temperature?

Do I need the sending unit for the oil pressure?

Is the wiring in the car for the sending unit or do I need to add wiring to the gauge?

MotoSook · 08:41 PM

Hi Keith.

What year is the combo gauge? The temp and oil sender (sensors) output ranges should match the guage, that is unless they were the same from year to year. That is not likely. When I swapped my motor, I was told by the seller (a well know Rennlister) that I would need to install the T and P sensors from my 2.7 motor. SO I did, and every thing seems fine on the car. I have been meaning to test both P&T for accuracy as seen on the gauge, but there have been too many things going on.

keitho64 · keitho64's Garage

I am not sure but I think it is a 72/3. Do you know if the wiring is there?

MotoSook · 02-25-2003, 08:59 PM

Ah, if I only had a long hood (I'll keep dreaming), I might know the answer to that. This might be tough, know the history of your car, but is there a pressure sensor on the motor (sorry if that's too obvious)?

To answer the question, I don't know. Someone will chime in about the wire I hope.

How goes the other work?

keitho64 · keitho64's Garage

Souk

The work went good. I have the chain tensioner covers done, oil thermostat o-ring replaced, drain tube o-rings replaced, heat exchangers installed and the flapper boxes adjusted to work.

What is left, mount the defroster and install the head light relays. Then it is time to drive. I do not think I will have it done this weekend. I have to many things going on so I doubt I will work on it.

If possible, I would like to get to Chris' Saturday. I am busy until 4:30 so if you are still out at 5:30 I may hook up with you.

MotoSook · 02-25-2003, 09:35 PM

I'll be leaving early on Saturday as I have a prior engagement, so I wont see you at Chris'. It's suppose to be close to 40 over the weekend, so if the salt is not too bad, I'll be driving the 911 some. Glad you are close with your car.

As for the wiring, I don't have any manuals that I can recall off the top of my head from which to pull out a wiring diagram for a 69. My factory manual CD only goes back to 72 I think. Don't know if the Haynes has a wiring diagram for a 69, but if it does, I'll bring it to Chris' house and leave it for you (if you don't have one).

Ping the Rennlist....seems like Walt or one of the Bruces should know. Wil F is hanging out on this board, he might know.

keitho64 · keitho64's Garage

Bump - Any ideas if the wiring for the combo gauge was installed for the T or do I need to run one? Also, ideas on the sending unit needed for the oil pressure and temperature?

dooop · 03-04-2003, 05:55 AM

Hello Keith,

I currently have the same kind of problem with my 68T with no combo gauge (oil temp + idiot light)

OIL TEMP :
My oil temp works upside down : The niddle goes to max temp at the engine start, and slowly lowers as I drive 15 minutes.
the Gauge works fine, each cable is at the right place, thus, I am considering to change my temp sending unit.
Temp sending unit changed in 68 (pre september : $250, post septembre : $20). The gauge changed in 69.
then, between 68 and 69, 2 different sending units worked on the same gauge, so, they should be compatible.

OIL PRESSURE :
On my 68T, I have oil pressure wiring, and no oil pressure sending unit.
According to me, you have the wiring and just have to install the oil pressure sending unit (along the oil tank).
The combo gauges were the same for T E and S through 73 at least, thus the sent information should be correctly readed by any of the gauge (simple or combo).

In my case, if the post 68 temp sending unit is not compatible with my gauge, I will replace the gauge for a combo rather than buy the $250 temp sending unit !
So let us know how it goes !!

Dooop

MotoSook · 07:28 AM

Keith, I was hoping you would have this worked out by now. But this is a picture of the sensors on my 3.0. It might give you an idea as to how to mount sensors. The oil pressure sensor is mounted on an adaptor which could be made to fit on any part of the pressurized system. The temp sensor is a bit tricky as it is longer than 1" (on my car) and screwed into the case. You might be able to tap into a spot that will allow the temp sensor to be screwed into, but this would probably be my resort.

If you can get matching gauge and sensors, it is possible to make it all work together.

Droop, I'm not very familiar with the early 911, so I'm just chiming in to help a friend so bear avec moi si vous plez

. Are you saying that the oil pressure is taken off the oil tank? I thought the tank was pretty must at atmosperic pressure. It is on the later cars (the SC's run a bit of vacuum I believe, for sure the 78-78).

An oil temp sensor bung might work on the oil tank, but I'll have to pull the oil system flow diagram to refresh the old brain as to how accurate the temp would reflect the temp of the oil circulating through the motor.

Good luck Keith.

MotoSook · 03-04-2003, 07:28 AM

dooop · 03-04-2003, 07:31 AM

Hello Souk,
You are right, I was confused with the oil pressure and the oil level sensor !

Does anyone know something about the compatibility between oil temp sensors in early cars

Thanx

keitho64 · keitho64's Garage

Souk

Thanks for the picture. It looks like I need to get the new sending unit for the pressure gauge and run a new wire from it to the gauge. As for the temp sensor, I will just connect it to the existing sensor and see what happens.

doop - it will be a while before I get the oil pressure sensor installed but I will post the results. For now, I am going to install the combo gauge with the oil pressure idiot light connected and the existing temp sensor to the new gauge and see what happens.

CamB · CamB's Garage

Hmmm, I had a combo gauge stuck in mine. There is some dicking around required as '69 is the last year where the gauges are mounted from behind (not the rubber ring friction method).

I can't remember if the mechanic needed to run wires for the gauge (for pressure). The easiest way is probably to see if the wire is in the harness back in the engine bay somewhere. You do need to match the gauge and sender, but I am no help as:

a) I didn't do it
b) I have a 3.0 back there

In fact, for all I know my gauges and senders aren't matched (and I'm getting more PSI and less temp than the gauges say!). I'm just paranoid because it makes oil pressure spec when hot but not by much, and because the temp goes to 210 rather than sticking at 180 despite big ol' oil coolers.

dooop · 03-07-2003, 04:24 AM

Breaking news :
the post 68 oil temperature sending unit fits in a pre-68 engine.
Moreover, the sent information are well recoglized by the gauge.

It did not solve my problem (my gauge still dispoay upside down temperature), but avoided me to buy a $250 early type Oil temp sending unit.

Dooop
(still looking for solution for the oil temp jauge !)

dooop · 05-27-2003, 01:39 AM

Ok, this was a long time ago, but I finally installed the combo jauge this week end on my SWB 68T.

I already had a new oil temp senter connected to my non-working temp jauge.
I installed the pressure sending unit (approx $30) and I found a reliable combo jauge from a friend of mine for $25.

Everything was pre-wired in the engine compartment.
I just had to disconnect the idiot light high pressure sending unit and connect it to the new pressure sending unit, and connect that one to the combo jauge (really easy).
Only a ling between 2 ground on the combo was missing.

Be careful, the SWB jauges are thinner that the later models (up to what year ?) My jauges are stuck with 2 screws and 2 bolts that are not on the later models (Pull the jauge and it comes).

Other information : I also wanted to replace the fuel level jauge with a "combo fuel and oil level" jauge.
I bought the oil level selding unit (the one in the oil tank) for $90, and figured out that my early oil tank was not "drilled", thus the sender is impossible to install. So, I kept my fuel level jauge...

Sorry for my written english...

Dooop

CamB · CamB's Garage

I bought the oil level selding unit (the one in the oil tank) for $90, and figured out that my early oil tank was not "drilled", thus the sender is impossible to install.

Same in a '69 with no oil level gauge. Cheap bastards at the factory!

keitho64 · keitho64's Garage

It is finally fixed and working.

Since my car never had a oil pressure gauge I did not have a wire for the sending unit. I ran a new wire to resolve that issue. However, after I installed the new the gauge still would not read. I tried cleaning the contacts, but that did not help. In researching part numbers I was sure I had the correct sender/gauge combo. Last night I pulled the oil pressure gauge out of the combo unit. I found that the needle was bent into the face of the gauge. I straightened the needle out and now the pressure gauge is working correctly.

I am using the stock temperature from the 69T and the gauge reads 180-200 in stop and go driving so I will assume it is close to being correct. It stays at 180 most of the time but will creep up to 200 if I push it hard for a long time or if I let it idle for a long time. When I first wired up the temp gauge, it did not work. I removed the lead from the sending unit and cleaned off the contacts and that took care of the temperature.

I left the oil pressure idiot light connected, the alternator idiot light is still connected and the parking brake light is working as well. Now I have a dash full of working gauges.

Thanks for everyone's help.