[DeTomaso] Water temp gauge question

larry at ohiotimecorp.com larry at ohiotimecorp.com
Thu Mar 19 11:29:21 EDT 2020


Steven,

I would stop working in the garage and move to the kitchen.

You will need:

Gauge
Sender
12 volt battery
Pan of water
Thermometer
G;ass for the stove (sorry stuck on an old post)
Jumper wires with alligator clips.

Hook it all up and slowly heat the water and make sure everything works as it should and see how accurate the gauge is too. You must start from a point of knowing the parts are good. Doing so in the kitchen gives you full control of the testing.

Install the sender in the car but wire the gauge by the motor. You can use the power wire from the harness to make sure the supply is good. Add and remove ground wires. Move the gauge around, use long jumper wires and you shall find the problem.

So what you are doing is starting with know good parts and using a logical (at least in my mind) progression to find the problem.


Remember that using a digital volt meter (DVM) is a great tool but it puts little to no load on the circuit it is testing. Many times it will show 12 volts + on the display but under a load it is nothing. I have an old headlight that I use as a load. The brightness of this old school tester can also give you indications of the amps being used when placed in line.


Larry (out of g;ass) - Cleveland




-----Original Message-----
From: DeTomaso <detomaso-bounces at server.detomasolist.com> On Behalf Of Mike Drew via DeTomaso
Sent: March 18, 2020 7:46 PM
To: Steven Edwards1969Dart <gsedwards at cox.net>
Cc: detomaso at server.detomasolist.com
Subject: Re: [DeTomaso] Water temp gauge question

Steven,

My initial guess is that you accidentally bought a 351C temp sender for a LIGHT which is an on/off switch rather than a variable switch, like you need. 

Please tell me you are not trying to fit the temp sender to the water tank?  That was a very bad idea De Tomaso had. All other 351C-powered Ford cars had the temp sender mounted in the front of the block, right next to the water pump, and below the thermostat housing opening. Pantera engines have a plug there. You should remove the plug and install a known good sender there, then install the plug in the tank where the sender used to be. 

After all, you care about the temperature of the water in the engine, not the tank. My very first (of many) Pantera failures was down to the stock design. I had a water hose come adrift and started leaking water. The temp gauge initially went up, but then the gauge started coming down (because it was no longer submerged in water). I thought the problem had fixed itself until the car erupted in a cloud of steam. I was very lucky I didn’t totally grenade the engine. 

Since you are horsing around with the system anyway, now is the time to fix it. 

Cheers!

Mike

Sent from my iPad

> On Mar 18, 2020, at 13:47, Steven Edwards1969Dart <gsedwards at cox.net> wrote:
> 
>    The water temp gauge was not working in the 72 that I am working on. It
>   was stuck on 90 and would not move.
> 
> 
>   I bought a new 90-260 water temp gauge and a sending unit that would
>   work with the gauge. I installed both, sending unit in tank.
> 
> 
>   When you run the key the gauge now maxes out to the right 60 degrees.
> 
>   So I check the system;
> 
>   Gauge is grounded
> 
>   Gauge has 12 vdc to it
> 
>   The red w/blk wire has continuity for the gauge to the sending unit
> 
>   Tank to body has continuity
> 
>   Bung to body has continuity
> 
>   Bung to base of sending unit has continuity
> 
>   Base to stud does not have continuity, which it shouldn't have until it
>   warms up to operating temp.
> 
>   I check the sending unit wire to body, no continuity, so wire is not
>   grounded to body anywhere.
> 
>   When I touch the wire to body the gauge moves to max
> 
>   Then I put the wire on the sending unit and it maxes out, engine is off
>   and cold.
> 
> 
>   I am in need of guidance to what is going on here. I am at a lose as to
>   what is happening.
> 
> 
>   Steven Edwards
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