[317th FMS]

Just thought I would pass on some info that might prevent a headache for someone else. The replacement water temp senders are not correct for the early Birds (GM Borg Warner etc.) they have the wrong resistance values. They give a 20 degree higher reading making you think you have a overheating problem. I temporarily installed a mechanical gauge and got 190 which is OK. Then replaced sender 3 times. Then the gauge. Then the printed circuit on back of cluster. Giving up I sent gauge and sender to get calibrated and they told me what was going on with the sender. I have seen a few correct ones on Ebay. They have the AC Delco script on them. Maybe someone else can chime in with there experiece on this.

[2manyT/A'S]

Good INFO!

Thanks for sharing.

[RicksGTO]

Good post as this is not something you want a false reading on for sure. Lectric Limited has correctly calibrated sending units as well. I have been told by several people about them and have one but the car is not running yet so I can't give feedback on their accuracy first hand yet:
http://www.lectriclimited.com/mainpage.htm

.

[317th FMS]

25.00 for lectriclimited sender sounds like a bargain compared to what I paid. Wonder how many radiators and water pumps were replaced because of this sender problem.

[CaptCrunch]

THANKS!.........good to know..........

[giles]

I ran into this issue as well. High gauge indicated temp shortly after a fresh rebuild, recore rad, etc. Checked it with an infrared temp reader - 195F! right where it should be. Borrow or buy an infrared temperature checker before you start replacing alot of expensive stuff. Point it right at the thermostat housing to check the real temperature.

[70RAlll]

I had this same problem years ago. Bought one from Electric Limited or H&H..can't recallw ho it was, and it was still wrong.. The difference is "with guage package" cars(TA"s and Formy's) have a different sender. Most repo senders just use the more common dumb light sender which reads wrong. Maybe the repo's are correct now.. But there is no "calibration" with these, they are not adjustable. Either they aremade correctly or not. Look at one, you will see...there is no way to open it up and change things out.. I suggest finding a used one on Ebay or finding a NOS one.. I bought numerous NOS ones for $75 or so.. I think I have 3-4 now, just to make sure I will never go through that again.. Maybe the repo's have changed the resistence, but yea ago they had it wrong.. Just my opinion and experience..Not trying to bash one company over another..

[njsteve]

Anyone know the correct part number for the original sender?

[njsteve]

Well, I bought one of the $25 Lectric Limited senders, installed it in the cyl head in the factory spot and it reads 25 degrees higher than the radiator water temperature measured with an accurate thermometer dipped into the coolant.

So much for the accurately calibrated reproductions.

On another site one of the guys opined that that the cylinder head mounted temp sensor will give a higher temp reading than the block location. This may be true, but that doesn't explain the accuracy of the original factory senders. Were they undercalibrated to compensate for higher cyl head temps?

[70RAlll]

Originally Posted by njsteve

Well, I bought one of the $25 Lectric Limited senders, installed it in the cyl head in the factory spot and it reads 25 degrees higher than the radiator water temperature measured with an accurate thermometer dipped into the coolant.

So much for the accurately calibrated reproductions.

On another site one of the guys opined that that the cylinder head mounted temp sensor will give a higher temp reading than the block location. This may be true, but that doesn't explain the accuracy of the original factory senders. Were they undercalibrated to compensate for higher cyl head temps?

Steve-

I hate to say it...but you know what is comming.,.."I told you so"... I tried one of these "calibrated" senders and same result. We must remember, the "guage" option was just that, an option. Our cars sold in way lower numbers vs total FB sales in any of the 70-73 ,model years. So , these manufacturers, are looking at the spec's for the majority of sales and calibrate to that. This is my opinion why they all have it wrong..

Steve, I told you that buying an original used one or an original NOS unit was the only way to go.. Now, with shipping, tax etc.. you are probably out another $40 or so.. This needs to be a constant thread on our board warning others not to waste the money. I will be suprised if the sender is returnable.. ANyway, shoot me an emaiul and I will find the NOS and used ones I have. Hopefully I have an extra used one. I seriously doubt I am letting go of the nOS units I have..

[njsteve]

No problem. It was around $30 so I figured I would be the guinea pig so nobody else would have to waste their money on an inaccurate sender. It's the least I can do for the site - in my role as official dubiously accurate parts tester.

I sent you a PM. A used original would be fine if you have one.

[RicksGTO]

Hey Steve, sorry it wasn't accurate, Lectric has a good reputation and they go out of their way to talk about how they've solved the problem but it sounds Bill was right. I've got one too but as I said I haven't been able to test it yet.

[eaglesan13]

I bought the Lecric one also but have not fired up my engine yet. However, I put the sensor in the intake manifold (72 cast iron intake) rather than in the cylinder head (6X-8). I guess we'll see if this makes a difference.

[Norwood]

Originally Posted by njsteve

Anyone know the correct part number for the original sender?

Best I can figure group 1.150 pn 6490384

[317th FMS]

APT instruments knows about this problem. I got the correct sender from them. It was NOS GM but had a threaded post instead of the spade button type. I cut the spade part off another and drilled and tapped it and screwed it on the threads. Looks original now and hope this makes sense and is understandable. If I knew how to post a pic on here I would. Chad

[Old Goat Racer]

Could this be the right one?

[njsteve]

No, that's the emissions/TCS sending unit that mounts on the passenger side cylinder head. It operates the solenoid that restricts vacuum to the distributor vacuum advance unit at certain temperatures.

[Old Goat Racer]

OK, but it's mounted in the intake manifold on a 70' GTO

[Old Goat Racer]

How 'bout this NOS one

[njsteve]

Yup. Thats the correct one but depending upon the year of manufacture it could be the later "one sender fits all" model.