It'* been a while since I've last posted but I need some advice. I replaced the coolant temperature sensor on my 1997 Bonneville SE 3800 series 2. I did it because I was flushing the system and it having over 200,000 miles I thought now would be a good time to replace it. After I reconnected the wiring plug and turned the ignition to run position the gauge needle instantly pegged full hot.Engine was cold. I replaced that sensor with a different brand and the same thing happened. I plugged the old one in and it worked as it should. I know that I should just run the old one but I've just got to know what'* going on.
All suggestions will be appreciated.
Russell

1997 was a transition year, but looking at parts I see that the temperature sender didn't change from 1996 through 1999 so you should be good. I do see different types of plugs on them, a 2-pin and a 3-pin. Assuming you got what yours already had, that shouldn't be an issue.

I think if the circuit sees a full open it will indicate full hot. I'll test it on mine if I have a chance.

Where did you get the new sensors?

What brand and part number was new sensor number 1?

What brand and part number was new sensor number 2?

CathedralCub, in all outward appearances the three look identical with three pins. The first was a Standard brand and the second was a Delphi brand. This morning I'm going to compare the ohm resistance between the original and the new. I do not know any of the values they should have but just to compare.

Forgot to list part numbers. Standard is TX66 (BWD:WT3024). The other is Delphi TS10032-11B1.

Interesting!

Usually when this kind of thing happens, we discover that the brands were Chinesium of some sort. I didn't expect to hear Delphi.

Looking forward to your results!

I have the original sensor back in and the gauge acts normal. I guess the old saying "if it ain't broke don't fix it" is more true than I thought. I checked the ohm resistance between all three units. I don't know what the readings are supposed to be but I just did a comparison. The original and the Delphi showed no continuaty between any two pins but the Standard showed 0.2 ohm resistance between two of the three pins. I'm sure I didn't accomplish anything but I just wanted to do it. I didn't go to the trouble of submerging them in hot water, the issue was when the engine was cold anyway.
Thanks for responding to this post and if you think of anything let me know please.

Thanks for the follow up!

I can't think of anything new except to ponder doing the same experiments on a plethora of temp senders.

For what it'* worth, my 1997 LeSabre has the factory temperature sender installed. At over 27 years and 257,000 miles old, it has always read accurately.

Well, CathedralCub, I've got an update on my temp sensor issue. I just hate being out done by this, so I tried an ACDelco brand sensor. I've been under the impression that they manufactured or at least furnished these sensors as OEM and GM recommended. Finally, this one worked as it should. I didn't have much confidence it would be any different because I couldn't' be so unlucky to have two previous sensors back-to-back faulty but that seemed to be the case. Oh well we'll see how it goes.

Thanks for the response to my post,
Russell

Wow, okay. Live and learn I guess!

I would expect the others to nearly mimic the performance of the OEM unit . . . and also to not be faulty.

whichever it was for each of them, I'm glad you got a part that works well!