Temp-Press light Coming On

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Temp-Press light Coming On

Postby Howler73 » Sun Jun 02, 2013 10:22 pm

Hey guys, I hooked up the wire from the dashboard temp guage in my 75 Monza with a 350 in it. I got one from a local parts store and put it in a plugged opening on the Edlebrock Performer manifold the previous owner had installed. The temp guage appears to work normally and read around 175 when things are warmed up. However then the temp-press light starts to slowly illuminate as the engine gets hotter but it never reaches full illumination. I pulled the connection to the sender and the light goes out. Anyone know what's going on?

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Ken
1975 Blue Chevy Monza, 350ci, 4 speed
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Re: Temp-Press light Coming On

Postby cjbiagi » Sun Jun 02, 2013 10:50 pm

It's possible that the sender you purchased is not calibrated correctly for the original gauge. Many replacement ones will read accurately with the stock gauge. The temp/press light will illuminate if the engine gets too hot or if the oil pressure is too low. Does the light only come on at idle? Your best bet is to always get an original GM sender if possible.
Clyde.........75 Monza 2+2
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Re: Temp-Press light Coming On

Postby Howler73 » Sun Jun 02, 2013 11:34 pm

Clyde, the light comes on at idle and at highway speed. When it starts it goes from completely off then gets real dim and gets brighter as the engine heats up but it never fully illuminates. Its definitely seems to be related to engine temp. I did the check the oil and its it's full. The engine only has 27000 miles on it. It was a new crate motor so I don't think it a oil pressure problem. I got another temp sender from Rock Auto so I'll try it.

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Re: Temp-Press light Coming On

Postby cjbiagi » Mon Jun 03, 2013 6:26 am

If that sender doesn't work we need to look for a correct GM one, not sure if they are out there or not but I could search.
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Re: Temp-Press light Coming On

Postby spencerforhire » Mon Jun 03, 2013 6:29 am

The warning light and gauge are not supposed to share a sender. The light should be connected to a separate sender the is open below something like 250 f and closed(connected through the metal housing to ground) above that temperature. The gauge sender produces a variable ground; if you disconnect the wire, it goes all the way down, and if you touch it to ground it goes all the way up.
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Re: Temp-Press light Coming On

Postby cjbiagi » Mon Jun 03, 2013 9:41 am

That is correct, there are two temp senders, one on each head from the factory. One is a gauge sender and the other a switch for the light. I kind of forgot about that. You could have a flaky sender for the light. Remember, this light works off of both temperature as well as oil pressure (kind of strange) but either sender could give you the symtoms you are seeing.
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Re: Temp-Press light Coming On

Postby Howler73 » Mon Jun 03, 2013 4:11 pm

You know all I did was connect up a wire that was laying in the engine compartment on the drivers side. I thought that when the previous owner had put the crate 350 in it he didn't put in a sender on that side's cylinder head and all I had to do was hook it up to a sender. I decided to put a new sender in the intake manifold as he used the stock exhaust manifolds and didn't take off the heat shield on that side so it would have been a pain to replace it in the stock location. Any idea which side's sender goes to which indicator ( light / guage)?
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