The Ford Barn

SR Pieper · 04-26-2020, 08:36 PM

I am trying to solve why my temp gauge reads 'cold' even though the engine is warm (not overheating). I have read the posts educating me on the two senders (8BA) that are on the heads but I don't understand if the wire connecting them together is sensitive to what post (long one vs, short one) on the sender that has two terminals. Looking at the systematic drawings of the two, by my guess, it is important the way the wire is hooked up. If it is important, what goes where ? Thanks

JSeery · 04-26-2020, 09:17 PM

The sender with two terminals is just an on/off switch which is normally closed. The sender with one terminal varies with the temperature. The wiring is from the gauge in the dash to the two terminral sender and then to the one terminal sender. There are a number of past threads that go into detail on testing the gauge and the system. Which terminal on the two terminal sender is not going to matter, but why not connect it as shown in the diagram?

A Cold reading would indicate a short to ground somewhere and Hot would indicate an open.

JayChicago · 04-26-2020, 09:24 PM

I think it's just a normally closed switch opened by high temperature . Doesn't matter which way a switch is wired. I think problem is elsewhere.

When you say "gauge reads cold", do you mean the needle doesn't move off the bottom? Or do you mean its in the lower range of the scale?

JSeery · 04-26-2020, 09:28 PM

Quote:

Originally Posted by JayChicago

When you say "gauge reads cold", do you mean the needle doesn't move off the bottom? Or do you mean its in the lower range of the scale?

Good point!

SR Pieper · 04-26-2020, 11:05 PM

Thanks for your quick reply. With the engine cold and the ignition is on, the needle is pointing to the 'C' (where it should be). After driving the car for 15-20 minutes, the needle goes off the scale (beyond) the 'C' side. The needle is supposed to move towards the 'H' side. Things are backward so that's why I thought I had the wires crossed at the sender(switch). Should I switch the wires at the gauge?

JSeery · 04-26-2020, 11:27 PM

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Have you checked the engine temperature so you know what it really is? An IR heat gun is good for this. If you do a search you can see how to check the gauge with "D" cell batteries.

Also, what year vehicle/engine are you working with?

flatheadmurre · 04-27-2020, 12:13 AM

Unhook the one terminal sender and turn the ignition on...if meter goes to high and stays there...sender needs attention.
Still on cold...unhook wireharness cable from 2 terminal switch...if meter goes to high you have a short in this or wire to one terminal sender...otherwise you have a short in the wiring harness.

04-26-2020, 08:36 PM	#1
SR Pieper Junior Member Join Date: Apr 2012 Posts: 2	Flat head temp sender/switch I am trying to solve why my temp gauge reads 'cold' even though the engine is warm (not overheating). I have read the posts educating me on the two senders (8BA) that are on the heads but I don't understand if the wire connecting them together is sensitive to what post (long one vs, short one) on the sender that has two terminals. Looking at the systematic drawings of the two, by my guess, it is important the way the wire is hooked up. If it is important, what goes where ? Thanks

04-26-2020, 09:24 PM	#3
JayChicago Senior Member Join Date: Jan 2019 Location: Chicago Posts: 732	Re: Flat head temp sender/switch I think it's just a normally closed switch opened by high temperature . Doesn't matter which way a switch is wired. I think problem is elsewhere. When you say "gauge reads cold", do you mean the needle doesn't move off the bottom? Or do you mean its in the lower range of the scale?

04-26-2020, 11:05 PM	#5
SR Pieper Junior Member Join Date: Apr 2012 Posts: 2	Re: Flat head temp sender/switch Thanks for your quick reply. With the engine cold and the ignition is on, the needle is pointing to the 'C' (where it should be). After driving the car for 15-20 minutes, the needle goes off the scale (beyond) the 'C' side. The needle is supposed to move towards the 'H' side. Things are backward so that's why I thought I had the wires crossed at the sender(switch). Should I switch the wires at the gauge?

04-26-2020, 11:27 PM	#6
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: Flat head temp sender/switch Sponsored Links (Register now to hide all advertisements) Have you checked the engine temperature so you know what it really is? An IR heat gun is good for this. If you do a search you can see how to check the gauge with "D" cell batteries. Also, what year vehicle/engine are you working with? Last edited by JSeery; 04-26-2020 at 11:32 PM.

04-27-2020, 12:13 AM	#7
flatheadmurre Senior Member Join Date: Apr 2015 Location: Sweden Posts: 3,045	Re: Flat head temp sender/switch Unhook the one terminal sender and turn the ignition on...if meter goes to high and stays there...sender needs attention. Still on cold...unhook wireharness cable from 2 terminal switch...if meter goes to high you have a short in this or wire to one terminal sender...otherwise you have a short in the wiring harness.