Topic: Engine temp gauge question

[evob]

hey all, hope everyone survived the winter months. I hope this post is in the right place because it's a bit of an electrical and drivetrain question. So here's some background to the question. About a year ago I put aftermarket gauges in my 79 trans am, just cheap ones nothing special. A year later I miss have the original gauges so I'm going to put them back in. But when I bought the car there was one gauge that was already an aftermarket gauge and that was the water temp or coolent temp gauge. I know that there is a fitting that goes into the air intake close to the front of it, but where is the one for the stock gauge? For me there doesn't seem to be a hookup that goes from the stem that read the temp, to a connection that leads to the gauge. Hopefully that all makes sense. Any help would be great. Thanks

[ta78w72]

In the head, between cylinders one and three.

[evob]

In the head, between cylinders one and three.

Sorry it's taken so long to reply I've been slammed with work. The picture below is all I see on top of the engine.
I took a picture of the head between cylinder one and three but I don't see anything there either


Thanks, Brant

[ta78w72]

Oh, you have a 403.  You don't have a stock set up.  The temp sender should be in the intake on the drivers side.  The port that's nearest the center. 

[evob]

So is the one that's in red the temp then?
Because the one in green is an aftermarket one that came on the car when I bought it



Thanks, Brant

[evob]

Oh sorry, I didn't know that the other motors had different set-ups but you are right. I have the 403 engine, don't know if that is a good or bad though haha.
So is the one that's in red the temp then?
Because the one in green is an aftermarket one that came on the car when I bought it



Thanks, Brant

[ta78w72]

The 403 is a perfectly fine engine.

Both those go into the cooling chamber so either one will work.  The green one should have a vacuum switch.  The red one is where the factory installed the temp sender.  Now, the unknown is whether or not that temp sending unit in the green circle has the same ohm spec as the factory gauge.  You could connect it and if you get a bad reading it would be an indication that the sender is wrong for the factory gauge.

[evob]

The 403 is a perfectly fine engine.

Both those go into the cooling chamber so either one will work.  The green one should have a vacuum switch.  The red one is where the factory installed the temp sender.  Now, the unknown is whether or not that temp sending unit in the green circle has the same ohm spec as the factory gauge.  You could connect it and if you get a bad reading it would be an indication that the sender is wrong for the factory gauge.

Sorry for not replying in so long, things have been crazy lately. The one circled in green is an aftermarket gauge that can with the car. The one in red, I followed the wire to the air box, which lead into some kind of control unit.

[evob]

Okay so I figured out that the green circle is for the aftermarket gauge. And the one is red is for the factory gauge. I follow the wire and it leads to a small black box next to the a/c box, after that it looks like it splits off or something. Any ideas?
I also should mention that when the car warms up the gauge stays at zero basically
Update: so I went and tried some tests this morning, I followed this guide http://transamcountry.com/community/index.php?topic=44283.0 for jumping some wires. That made the gauge from from dead zero to just under 100 on the gauge. I turned the car on and let it run for 15 min and took an ohms reading from the temp sender and got 350 ohms at 150 to 160 degrees F. According to ILLTA77 at transamcountry I should be getting readings like this:
220 degrees = 70 ohms
200 degrees = 90 ohms
160 degrees = 140 ohms
120 degrees = 250 ohms
100 degrees = 340 ohms
 68 degrees  = 638 ohms
I want to say the sending unit is bad but I have no idea.