Temperature Gauge sending unit

[FuturaGuy]

Ever since I did my Modular conversion with a '98 engine and an '88 dashboard, the temperature gauge has never worked. When I had to drain the cooling system once for another reason, at the same time I changed the gauge sending unit with a new one I got at NAPA and kept the old one. According to the '98 shop manual, the resistance of the sending unit is 74 ohms cold and 9.7 ohms hot. Both my new sending unit and the old one read between 1500 and 1700 ohms cold. I think the shop manual may be wrong (that's not the first time it's been wrong) and I should install the sending unit from an'87-'93 5.0. Has anyone else had the same problem and does anyone know what the resistances are supposed to be on the 5.0 sending unit?

The car has never overheated, even last July when I was in a traffic jam caused by a 4-car accident on the Cross Island Parkway on Long Island. Notice I said the car didn't overheat, which is more than I can say about the driver. Seriously, I'd like to have a temperature gauge so I'll know what the engine is doing.

 

[Svt Fox]

Have your tried using a fox temp sensor?

 

[FuturaGuy]

That will be the next step but before I do that I want to test the gauge to make sure it's good. That's why I asked about the resistance range of the Fox temperature sender so I can put resistors of the low and high values in place of the sender and check the gauge readings. I really don't want to change the sending unit unless it's absolutely necessary - messy job.

 

[Svt Fox]

The fox sending unit has worked pretty well for me over the last 3 years, in my 4V swap.

It can't be any messier than changing a 4v's thermostat..

 

[FuturaGuy]

Today I changed the sending unit to an '87-'93 Fox unit and also fixed a small leak in the thermostat housing. You were right - I got a shower with antifreeze. At least it wasn't hot. Tomorrow I'll put in a new electrical connecter for the sending unit and do a road test.