[pggto]

I'm putting the original parts back on the 71 GTO I purchased. I'm trying to figure out which temp sending unit I need. The car has lights, and the new wire harness just has one green wire for the sending unit. Some research shows that I should have a multiple terminal sending unit? Which sending unit do I need? I pulled what I believe is the remains of the original sending unit out of the aftermarket intake that came off it, and the number on it is AC 253M if that means anything. Thanks for your help.

[thepontiacman]

I have those sending units, if you need one. $50.+ Shipping.
Used original part. Email me with that number on your old one.
thepontiacman@yahoo.com





Sent from my XT1650 using Tapatalk

[pggto]

[QUOTE=thepontiacman;6141162]I have those sending units, if you need one. $50.+ Shipping.
Used original part. Email me with that number on your old one.
thepontiacman@yahoo.com



I'm still trying to determine which is the correct one? Is it the sensor with the nail head or does it have one or multiple spade terminals? Thanks

[Paul E]

Take an ohm meter reading. For a light it should be open and when it overheats the connection is made and the light goes on. If the sending unit you have has a resistance value it is for a gauge (or bad). Good luck!
Paul

[Ben M.]

Originally Posted by pggto

Is it the sensor with the nail head or does it have one or multiple spade terminals? Thanks

Multiple spade terminal is correct. The nail head one is for gauges. If you have a gauges car, they used both with a different green wire over to the nail head alone. Does your new harness have the 3 prong connector like shown?

[pggto]

Originally Posted by Ben M.

Multiple spade terminal is correct. The nail head one is for gauges. If you have a gauges car, they used both with a different green wire over to the nail head alone. Does your new harness have the 3 prong connector like shown?

Thanks for the reply. Is that a 71 or 72? I think there different? My sending unit is actually on the other side of the intake, and I don't have a connector like that in my harness?

[pggto]

I'm trying to find the correct replacement one. Not sure what it used to be because the head is broken off. I'm trying to put the original parts back on the car. I'm currently just placing items in place to see whats missing or is wrong. Thanks for your replies.

That is not the correct sending unit in the intake at the moment, just stuck in the hole by a few threads.

[69gtocv]

Originally Posted by pggto

Thanks for the reply. Is that a 71 or 72? I think there different? My sending unit is actually on the other side of the intake, and I don't have a connector like that in my harness?

I'm not up on my 71's, but the three spade connector temperature sending unit was moved to the rear of the passenger head in 72, then a separate sending unit at the front of the drivers head if you had gauges. The spot on the right side of the intake manifold like shown in his picture was where the TVS switch was that got vacuum from the carb, then one line went back to the CCS switch (that basically didn't allow vacuum to the dist vac can until the coolant temperature reached a certain level and if the transmission was in high gear), then another line to the charcoal canister. ANYWAY, I'm going to put my 3 spade temp sending unit in that same spot on the right side of the intake because someone put 69 heads on my 72, so I don't have the hole in the head that 72 needs. Again, not much help for you, but you wanted to know if that was 71 or 72.

[69gtocv]

So according to a MPC parts book I found, the switch for 71's should be a 6490152. I found this NOS one on the net

https://www.oldsobsolete.com/product...ch-gm-6490152/

Looks like it should have a 3 prong connector from your harness though? You're saying you don't have that

Jeff

[gto4evr]

Originally Posted by 69gtocv

So according to a MPC parts book I found, the switch for 71's should be a 6490152. I found this NOS one on the net

https://www.oldsobsolete.com/product...ch-gm-6490152/

Looks like it should have a 3 prong connector from your harness though? You're saying you don't have that

Jeff

Jeff's correct along with Ben's pics. 3 blade in the intake for 71. You can downgrade to a cheaper single pole blade like 69's if you're not running a TCS switch, just get the right wire to the single blade to run the idiot light

['ol Pinion head]

Originally Posted by Ben M.

Multiple spade terminal is correct. The nail head one is for gauges. If you have a gauges car, they used both with a different green wire over to the nail head alone. Does your new harness have the 3 prong connector like shown?...

That's only on 71 Dport cars. '71 455 HO equipped cars will all have the multi port vac switch in the passenger side of the water crossover, then w factory AC, 71 HO cars use the 3 prong switch on the drivers side whether std guage or rally guage.

['ol Pinion head]

should have several nice 71 application 3 prong switches.
'70's have a different part number & heat range inscribed on them, have '70's as well.

[Ben M.]

Thanks oPH. My experience is limited to mostly the '72 poor-boy cars (no HO cars here! ;-) ) and they did have the 3 prong sender in the rear passenger head and a 2nd nail head sender in the driver's side front for gauge cars. I've had 1 '71 and it was set up as I showed.

Good thing we have a group of people who have a multitude of cars to keep things straight!

I will say that I had a car with a reproduction engine harness and it was labeled as "'69-71 GTO" on my '69 and it didn't have the 3 prong plug in it...

[pggto]

Just wanted to do a follow up. I left some info out on my first post. I'm trying to reassemble a 71 455 HO GTO w/o gauges (idiot lights). After doing some research there is only one 71 455 HO wiring harness available, there for there are two different sending units for the one wire connector with the nail head. The sending unit for the non-gauge HO is 6490153. Believe it or not I actually found one. Thanks Uncle Judge for your help on the research.