Hello ..got a 89 Bronco II th other day ..

lohanso · 05-07-2008, 07:06 PM

Changed the temp sending unit but the guage still doesn't work ..agh ..any ideas ?

jonmark1985 · 05-07-2008, 07:17 PM

a broken wire?

adrenochrome · 05-07-2008, 08:50 PM

The connector going to the sending unit should only be 2 wires... If it has more, then its the coolant temp sensor you just changed... If it does have 2 wires, short them together and check the gauge inside the dash and it should be maxed out, if it didn't, it's more likely that it's not making a good enough connection to the sending unit or could be a "broken wire".

lohanso · 05-07-2008, 11:28 PM

nope ..just one wire ...checked the old sending unit with an ohm meter/ unit in a pot of water on the stove and it responded OK except for an infinite resitance when cold ...book said it should be around 75 ohmsgoing to 7.5 ohms at 200 deg..so I replaced it.

Didn't help the problem replacing it ...

jonmark1985 · 05-08-2008, 05:22 AM

you're right there is just one wire on it, not two

Have a friend watch the gauge, turn the key to run, and ground out the wire to the sender and see if the gauges needles out really fast. Only do this for a second as I have heard that it could burn the gauge up if you let it go for any amount of time, usually I just pop a wire in the end and tap it against the block.

You may have got a "switch" for a temperature warning light, instead of reading variable resistance it will read on or off depending on temp, which off would be the infinite resistance that you see.

lohanso · 05-08-2008, 07:03 AM

I did get a steady decline in resistance once it "blinked" off infinity, changed it out hoping for a easy (and inexpensive) fix. I'll try the grounding tip.

The gas tank gauge does not work either, could they be related ? Oil and charging gauges work OK.

Thankyou for your help

jonmark1985 · 05-08-2008, 07:06 AM

They may be on the same fuse, but otherwise they aren't really related.

lohanso · 05-08-2008, 10:48 AM

got power (5.8v) to the sensor so I've ruled out a fuse anyway. Gonna round up a resistor and try the grounding tip ..

lohanso · 05-08-2008, 11:42 AM

I must not have driven long enough after replacing the sensor, or as it's warmer today maybe the thermostat is frozen open (or none existant) and it got warm enough to read.

Whatever, a new problem just popped up on the way to get the vehicle inspected. Right front caliper is dragging ...might get started tonight, might not ...

Thanks again for all the suggestions !