Hello. I have searched and googled and scratch my head for a while. I have a 307 oldsmobile, Vin y/9 with the 5A heads on it, making it an 81-85ish motor, in a 1978 Pontiac Grand Prix. My Grand Prix has a temp gauge, oil pressure, voltage etc. The Voltage and oil pressure work fine. The temp is at zero and doesn't budge. I am trying to figure out where the temp sender on my block would be, since I am sure it had one hooked up and has just been broken/gone bad, so I can replace/diagnose the issue and replace it. Once I know where it should be, I will pull the fitting, find a replacement and diagnose wiring from there.

I would absolutely adore either being told where it is or a picture of where it is and what it should look like. If possible, a part number would be amazing.

 

Oldsmobile temp senders will always be located in the coolant crossover at the front of the intake manifold. 307 motors have three ports in that crossover, The outboard port on the driver side is used for the coolant temp sensor that feeds the computer, the inboard port on the driver side is the temp sensor or switch for the temp gauge or idiot light, and the port on the passenger side is used for the thermal vacuum switch that operates the evap system.

 

So, replace the inboard, make sure it is hooked into the gauge properly. I have seen the "temp sensor or switch" for the temp gauge and pictures of this. Does switch mean it turns on a "Hey this is too hot" light and sensor mean it relays actual temp info to the gauge, giving you a best guess of the coolant temp?

 

The idiot light uses an on/off switch that closes at about 238 deg F. The gauge uses a sender that has a variable resistor. They are different parts.

 

You are my hero. Between the picture and the description, you are probably preventing my car from over heating.

You have a part number for that?

 

Use the temp sender for the instruments in your car. Google is your friend.

 

And FYI, since your car doesn't have a computer, I'm assuming at least one of those ports is plugged or has an unconnected original sensor in it. You can put the new temp sender in any one of those three ports. It will work the same.

 

Ok thanks! I really appreciate the information.

 

I got a bit antsy about this, started looking for parts online. I then went and looked at pictures of my cars engine. The inboard port, for.... whatever reason, has the throttle return spring stretched too it.....

I just don't know anymore.

 

What exactly don't you know? All three ports are the same thread. A coolant sending unit screws into any one of them. The temp reading will be the same at any one of them. The factory 1981-88 307 installations needed three because of the senders for the computerized emissions controls. You car presumably has none of that. This isn't rocket science. Pick one, screw a new temp sender into it, and don't look back. We've spent more time talking about it than it takes to do it.

 

or post a pic of your intake

 

Do have bolt in the intake in that spot? As said, 3 spots. A site like Rock Auto shows which sender are for a light, usually a spade terminal. The button style are usually for a gauge. I usually try to match the sender to the vehicle. Pretty sure the factory sbc senders on my 78 and 94 Olds transplanted trucks screwed right into the factory #17, A4, Performer and SP2P Olds V8 intakes without adapters.

 

you gotta give the OP props for wanting to do this his/her self , getting their own hands dirty..... some of us never worked on cars that much as our interest or jobs did not allow it but now in our retirement years we can and get our hands dirty and will need to ask questions for help. If it offends you that some of us need to reach out , dont answer,, pretty simple

 

Or don't resurrect old posts with no information that helps to answer the questions that were asked.

Seriously, ask yourself how your post helped in this situation.

If you have a gripe about something, make a new post in the General Discussion or Clubhouse sectons and let fly.

 

x 2

 

I actually forgot about this thread. Never messed around with the temp sender after I posted this because of bad weather and covering the car to avoid snow. On a warm, dry(ish) day a few weeks ago my daily needed to go to the shop, so I drove my Grand Prix. Temp gauge still wasn't working. The warm weather vanished, it snowed on the uncovered car and I was waiting for it too melt to cover again. Went to start it the other day and the temp gauge sprung to life, but now it won't start.

The joys of classic car ownership right?

 

Hi Joe -

Old thread I know but I happened on it while working on my 84 Caliente. Both CTS and Sending unit pigtails are in really tough shape with exposed wires, cracked plastic and brittle rubber. Any suggestions/sources for these? Saw on the G body forum that 91 C1500 CTS and corresponding pigtail will work which is fine with me (driver not a show car) but unclear if temp sending unit would work as well (digital dash with guage). Any thoughts appreciated.
Gordon

CTS and Temp Sender pigtails are the same