[nhoth2o]

First of all hello all, here's my problem:

We're having a hard time locating a 3 prong coolant temperature sending unit. It actually goes on a 72 Pontiac Lemans 350 the P.N. (off the unit) AC-95M-230B-265M. The car has only a light (no gauge) and every place we look only offers a one wire or a two wire sensor but the original unit that came out of this car has three male spade connectors comming out of the top. Also if it help it screws into the head not the intake.

Here is a picture if it helps:

[Lloyd-TX]

That is the transmission controlled spark coolant temp swithc, which is located in the rear of the passenger side cylinder head. The "TCS" system controlled the vacuum advance through a solenoid mounted towards the rear of the intake manifold - for emission control purposes. The solenoid in turn was switch on or off depending upon vehicle speed (TH350 and TH400 equipped cars) or gear selection (3 or 4 speed manual transmission equipped cars). This switch you have pictured was an override to allow vacuum advance under all conditions only when the coolant temperature was well above normal.

GM part number is 6490384 and the AC-Delco part number is G1868. Both are long discontinued and no aftermarket parts were ever available. If you still want one for (resto purposes) keep an eye on e-bay, I found a NOS one there about a year back. Other than that, plug the hole in the head and simply route manifold vacuum directly to the distributor.

The single wire temp light sender should be widely available, and on a '72 Pontiac is screwed into the hole near the front of the driver's sise head.

Welcome aboard, and I hope this helps!

[70ramair455]

Looks like ebay # 4560058542 is your answer.

Good luck.

['ol Pinion head]

The e-Bay seller is wrong. The 3 prong sending unit used in '72 is different than one used in '70, & different yet from the one used on '71 HO engines.

[nhoth2o]

yeah I saw that one on ebay too..

Thanks for the info, we didn't know thats what it did. Here is where we are....we do not know if the one we have is good or bad, just going to replace (I guess we'll reuse it now), the solenoid must have been removed because it's not there. Also is it possible that this 3 prong unit also works the light? As there is a plug in the other head and no other sensor on the engine. We plan to fire it up soon, hate to have to drain the coolant to add a temp sensor later...

If you'd like to see the car heres a link to our site:
1972 LeMans

[70ramair455]

Ooops ... sorry if I messed you up. I was just trying to help. My apologies.

Good information ol' Pinion. I'm restoring (or should I say upgrading) my '70 and will have to watch out since I'm looking for correct parts.

Hey did you see the Oil Pressure (rally gauge) sending unit which sold as NOS for over $200 yet when I asked him the part number the one he gave me was NOT for a '70 Pontiac (or any other for that matter.) It looked totally reproed.

I bought one off Ebay with the part number stamped in that was sandblasted and repainted for less than $30. I hope it works!!

[nhoth2o]

Well, heres what I found out. This unit also works the idiot light. We couldn't figure out why the hole in the other head was pluged and assumed it had been done years back and the light just wasn't hooked up. because there is a wire on the left side that looks like it would be for the temp light. But we grounded it and the light did not work. After some time we discovered that the light is controlled by the 3 prong sending unit (3 fuses later)

The light is controlled by the single prong that is perpendicular to the two parallel plugs. Thanks for all the help. We ended up replacing the original and cut off the plug and are using only the temp light wire.