Jonmueller1

When I turn the key to the "on" position, I would expect the temperature light to momentarily go on and then go out once the motor starts. I have never seen this light go on at all.
My question is, how do I test it to make sure it will work in case the motor gets too hot?
1) Pull temperature guage light bulb and check. If bad , install new one.
2) Remove old sending unit and replace with a new one hoping that solves issue.
3) Install separate new after market temperature guage under the dash with a new sending unit included.

Can one take the wire that connects to the sending unit and connect that to the positive side of the battery as a valid test to see if the light works?

I know to many this sounds simple, but just wanted to get an opinion before delving into this issue. Than you all for your input. Jon M

joe_padavano

No. This is where you need to review the wiring diagram. This is also where you need to do some free troubleshooting BEFORE buying parts like a sender.

The sender provides the GROUND, not power. With the key in the RUN position, disconnect the wire from the sender and connect it to a good ground (or the negative battery terminal). If the light goes on, the bulb and wiring is working. If not, verify that the instrument fuse is good and that the bulb is good. I don't have my CSM at work, so I don't remember offhand if the 1964 cars had the "lamp test" feature or not. In any case, if they do, the lamp test simply provides a ground to the lamp with the key in the START position. This will only tell you if the bulb is good and getting power. It does nothing with the sender. The only way to test the sender is to check it for continuity while in a pan of boiling water (and even that probably won't test it, since the sender closes at 230-ish degrees, not 212).

Jonmueller1

Thanks Joe! I now know what I need to do next, much appreciated!

Jonmueller1

OK, did the test tonight connecting the lead wire from the temperature sending unit to a ground at the battery. The light came on and also stayed on when I turned the key to the run condition.
So if the sending unit is good, it would make the light come on once the temperature went beyond boiling point. Why not then just install a new sending unit and then you would be sure that it would work if the car overheated? Like you say, you need water to be hotter than boiling 212 to test the old one.

oldstata

Just because it's new doesn't mean it works. I have installed many new parts that don't function correctly

joe_padavano

Because that has NOTHING to do with your original question:

The lamp-test function in the ignition switch does exactly (and ONLY) that - it tests the lamp. It does NOT test the sender. The fact that jumping the lead wire to ground causes the lamp to turn on simply proves that 1) the lamp works and 2) the lamp test function in the switch does not work. Neither of those bits of information tells you anything about the sender. If replacing the sender lets you sleep better at night, knock yourself out. Personally I'd install a temp gauge instead. Understand that replacing the sender still will not cause the lamp to come on when the ignition switch it in START. That's either a bad switch or a bad wire from the switch to the TEMP light.

Jonmueller1

Joe: I follow you exactly. The light did work when I grounded it. The answer would be to install temperature gauge . Is there a way to install an electrical temperature gauge and set up a split so I can still keep the stock idiot light connected as well?

Second issue: I barely had the cold engine running just a few minutes because I just finished a radiator rebuild. As I was waiting for it to warm up, I placed my hand on the alternator and it was real hot already. Not normal it seems. The brand was something called "World Class" in the label, a replacement unit I put in some five years ago. It would appear the heat being generated on the exterior of the alternator would be from bad bearings or possibly a short. Should I replace it?
I know this the expensive way out, but I notice the recently replaced battery is overstimulated since there is white residue in the battery box. "Replace the alternator" seems to be the right choice. I am sure your wisdom is worth consulting on this issue. Thanks, Jon M.

joe_padavano

Yes, but unlike an oil pressure sender, the temp sender must be in flowing coolant for an accurate reading. You need to use two separate ports in the coolant crossover for the senders to both register properly. Not all intakes have this provision, unfortunately. It is possible to drill and tap an additional hole, or you can use an inline bung in the upper radiator hose. This is less desirable as it is only accurate if the thermostat is open, but it may be the only option.

Alternators do heat up, but that sounds like it might be excessive. Bad bearings would be screaming at you - you'd know it. I'd have a spare alternator on hand but I wouldn't replace this one unless there's an obvious problem. Is this an original-style external regulator system or an internal regulator system?

Jonmueller1

Joe: It would appear that the regulator is internal. All I know is that when I hook up the alternator, there is a square plastic end with a set of wires that gets connected to the back of the alternator, then a red wire that gets attached to the back of the alternator and is held on by a bolt. I do notice , however , is a square shaped black box about 2 inches by three inches on the fire wall. Not sure what that is, but wanted to mention it as you might know. Thanks, Jon M.

oldcutlass

The box on the firewall is probably your external voltage regulator. It should have a 4 wire connector on it, and possibly a condenser on top still.

joe_padavano

The original external regulator system on your car has a voltage regulator on the firewall that looks like this:



The matching alternator will have a plug that looks like this:



The alternators with internal regulator have a plug that looks like this:

Jonmueller1

Joe: I confirm what you said and your pictures are correct. The regulator is external. The wire you show for the external regulator is the one I have, and the black box is on the firewall.If the previous alternator gets real hot right at the outset, could the regulator play a part in this? Sorry I am not up on this, but these cars are 50 plus years old. I already bought a new alternator to replace the old one. If I need to test or check the voltage regulator to make sure it is working properly, what is the procedure there? Thanks, Jon M

rickrock999

[QUOTE=joe_padavano;872539]No. This is where you need to review the wiring diagram. This is also where you need to do some free troubleshooting BEFORE buying parts like a sender.

The sender provides the GROUND, not power.

Reviving an old thread I know, but I found this doing a google search, and it helped me solve my problem.
Thanks Joe, If you are ever in the L.A area and have the time I owe you several beers.