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How do I go about testing my coolant temp sending unit? I thought the gauge was bad but if I ground it out it goes to full.
The sending unit is brand new. Interesting thing was that my truck is a '67 however the motor must be a different year because when I picked up the sending unit for a '67 352 at AutoZone it was too small. Went back and had them lookup a '73 and it fit perfect. Was there supposed to be an insert in the '67 motor for the smaller sending unit? Would there be a difference in years that would make my sending unit not work? is there an easy way to test it?
Some new sending units are no good. Took me 3 tries to get one that would work....(maybe it had something to do with the tariffs...
Some recommend NOT putting any sealant or tape on the threads as it keeps the sender from grounding properly. I suppose you might be able to hook a ground to the sender to see if there is any difference.
My question would be.. would two different sending units work the same? Meaning.. at autozone they sell one for a '67 F100 that doesnt fit (but thats my year truck), so I installed the one from the 1973 which does fit. They look similar, obviously different threads. Should the both at least give me a reading? I uploaded pictures of both. The larger with the sealer is the one I ended up with.
Grounding does peg the meter. Verified that the sending unit has a good ground (grounded out the gauge cable to the sending unit base, pegged the needle as well).
Went to Napa and got a new sending until. Same thing. No gauge movement.
Set my multimeter to Ohms and turned dial to 20k. Here are the readings:
.29 hot
.04 cold
What else can I be doing? So confused. The PO did have an aftermarket gauge, so i am thinking something was up. Is it possible the stock gauge just isnt picking up the Ohms correctly? There was an engine swap done on this engine it seems.
Almost tempted to ditch the stock look and add an aftermarket Volt, Oil Press & Coolant Temp gauge.
Unless the '67 used a different range (I don't think so though) the range for Ford gauges (fuel, oil, water) is 73-10 ohms. With 73 being cold, and 10 being hot.
It's actually some odd number like 9.6 to 72.8 or something like that, but we always just round off as do the manufacturers of aftermarket sending units.
Not sure about your readings. Seem odd, but at least they go in the right direction (down as it gets warmer) but can you watch the meter drop slowly? Or does it just toggle between one and the other without variation?
If no variation other than high/low, then it might be a sending unit for an indicator lamp rather than a gauge with a needle sweep to work with. Or it might be defective.
Or it might need a different range on your meter. Never can remember which scale to use, but try some different ones on the meter to see if at any point you get a 73ohm reading cold.
Oh, and if you're electronically inclined, that's one way to test the gauges too. You can put a 10ohm resistor between the sending unit wire and a good ground to see if the needle goes to the top (without burying itself in the end!) or a 73 ohm resistor to see if it reads cold/empty/low.
Oh, and wait for someone to confirm the ohm range too. Ford has used at least two, if not three ranges over the years. But all the cars and trucks that I know of during your year used the 73-10 I mentioned. The early Broncos were that same range from the '66 model, and pretty sure they used that up until the era of computers.
Oh, and wait for someone to confirm the ohm range too. Ford has used at least two, if not three ranges over the years. But all the cars and trucks that I know of during your year used the 73-10 I mentioned. The early Broncos were that same range from the '66 model, and pretty sure they used that up until the era of computers.
Paul
Thanks Paul,
Ended up buying a 4th sending unit. This time from cgford down the street from me. Guess what? Gauge is working now.
So In the end the sending unit from O'Reilly, AutoZone and Napa all didn't work for me.
Odd. They all measured the same cold.
Oh well, thanks for all the help everyone.
Last question....where can I buy the push on connectors for sending units? Right now I have the eye connectors and I need a nut.
And some of the sending units don't even have threads. They just have "ribs" to catch the push-on connectors.
Usually most parts stores have them in blister packs on the spinner racks and shelves out in the showroom. But sometimes they have them behind the counter.
If you're lucky you can even find them correctly color coded, but most often the wires are just black.
And you might just take a sending unit with you (or have them grab one off the shelf) because I've bought push-ons that were either too loose or too tight before. Pain in the neck!
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