[64 Bonnie Ragtop]

I have a 64 Bonneville with idiot lights indicating when the engine is COLD od HOT. Neither of the 2 lights (COLD or HOT) on my dash have ever come on since I bought the car, so I just replaced the temperature sending switch. Now, the COLD light properly illuminates when the engine is cold and is warming up, and it goes out a few minutes after idling. The HOT is my problem. According to the owners manual, the HOT light is supposed to come on whenever the ignition switch is in the Start position, (when the engine is cranking.) This is not happenning. To ensure that I have power from the temperature sending switch back to the HOT dash light, I unplugged the switch, then I clipped a test wire to a ground strap, and clipped the other side of the test wire the female portion of the plug that goes on the HOT terminal of the temperature sending switch.... the HOT light on the dash illuminates when the ignition is in the ON position What is wrong...how come the HOT light on the dash not come on when I am starting the engine? By the way, the ignition swich was replaced last year.

Thank you very much for your assitance....I know someone here will help me!

Vince

[LPete]

Not positive about a '64, but on my '69 the temp light is grounded by the ignition switch in the crank position. There's an extra terminal on the switch just for that purpose.

[64 Bonnie Ragtop]

Lee,

Thanks for your response. I assume the 64's are the same...when cranking, the temperature sending switch should ground. Apparantly, something is not quite on my end....that's what I am hoping to find out and resolve. When you say that the ignition switch has an extra terminal, which terminal is it....do you happen to know the color of the wire? I have a spare NOS Delco ignition switch that I am looking at, and I can't tell if there is the extra terminal that you are referring to.

Thanks again for your input.

Vince

[LPete]

My ignition switch is going to be totally different (GTO column-mounted), so I don't think it'll help to describe it. I do believe, though, that the wire at the ignition switch would be the same color as the wire to the temp switch that turns the light on. Just to clarify, it's the *ignition* switch that grounds the circuit when cranking (thus turning the light on), not the temp switch. I think we're on the same page...

If I can find a '64 wiring diagram I'll make sure this is correct.

[LPete]

Yep, found a diagram at http://www.tocmp.com/tOCMP/wiring/Po...ing/index.html

The dark green wire from the light and the dark green wire from the sender meet at the ignition switch. Grounding any part of that circuit will turn the light on.

[stevep]

Vince, a non A/C ignition switch has 8 terminals and an A/C ignition switch has 9 terminals.

[64 Bonnie Ragtop]

Lee and Steve,

Thanks for your replies.

Forgive me for being dense, but I guess my next step in diagnosing and correcting the issue should be to check to ensure that the dark green wire from the light and the dark green wire from the sender meet at the ignition switch??? Thanks for the diagram.

Vince

[LPete]

They have to be hooked to each other there if the light works from the temp switch. The question is if they're hooked properly to the switch. Steve was hinting that the switch may be wrong, I think.

If they are connected to a terminal (the correct one) on the switch, the switch must be bad. Or possibly the switch is somehow not grounded?

Jump in anytime, Steve!

["QUICK-SILVER"]

The switch does have to be mounted tight/grounded to the dash for the ground terminal/bulb test terminal to work with the switch in crank position.

The ground terminal on ignition switch is just a stop off point for the dk green wire as it runs from bulb to sending unit.

Un-plugged from switch or switch not grounded doesn't stop the bulb from working if the engine over heats. You just lose bulb check while cranking.

[64 Bonnie Ragtop]

Lee and Quick,

Thanks for your responses. The switch is the correct one....8 terminal for non A/C equipped car. I believe the switch is good, and I believe it is grounded....I touched one end of a test light to a terminal on the fuse box, and the other to the body of the ignition switch, and the test light lit, so I assumed the ignition switch was grounded. Am I correct? Maybe not.

For the record, I will check to make sure it is tight to the dash, and I will also check on the 2 dark green wires (bulb to ignition switch and temp sending switch to ignition switch.)

Thanks, again.

Vince

["QUICK-SILVER"]

"I touched one end of a test light to a terminal on the fuse box, and the other to the body of the ignition switch, and the test light lit, so I assumed the ignition switch was grounded. Am I correct? Maybe not."

Correct with that assumption.

A continuity test from switch body to ground terminal on the back of the ignition switch with switch in cranking position will tell if the switch is making correct contact inside.
AND/OR
The same test you did from fuse box to switch body, just go to ground terminal on back instead. Switch will have to be mounted/grounded and in cranking position.

Might want to un-hook coil positive wire and tape it up so you don't have to worry about the engine starting or burning points while the switch is on during testing.

FWIW I tested a '68' model big car switch last night to verify ground function while cranking and it's a TEN terminal switch.

[64 Bonnie Ragtop]

"The same test you did from fuse box to switch body, just go to ground terminal on back instead. Switch will have to be mounted/grounded and in cranking position."

Quick,

So, I unplug the switch, then find the ground terminal,correct? How do I know which one is the GROUND terminal? I am looking at my spare switch, and I don't see anything marked, "GROUND".

Thanks.

Vince

[LPete]

Hi Vince,

The "ground" terminal Quick is referring to is the one the dark green wires are hooked to. That terminal should be grounded through the ignition switch in the crank position. With your test light hooked to battery power, touch the probe to that terminal. In the crank position the light should light, in any other position the light should be off. Again, this is with the switch properly mounted to the dash.

Basically you're substituting a test light for the "hot" light.

Lee

["QUICK-SILVER"]

Originally Posted by LPete

Hi Vince,

The "ground" terminal Quick is referring to is the one the dark green wires are hooked to. That terminal should be grounded through the ignition switch in the crank position.

Exactly
----------
The '68' switch I've got in hand has every terminal labled. I did probe every terminal to switch body doing a continuity test holding the switch in crank position. The one marked GRD is the only one that made the beeper go off and showed no resistance 0 ohms.
Do your spare switch the same way to see which ones the ground terminal. Hold it in crank position and probe them all.
As Lee said, it's the one the dark green wires are hooked to on the switch in the car.

Don't know what the chances are of GRD being in the same location between these different year models, but here goes. Looking at the switch from the back with key off standing straight up, GRD is the furtherest horizontal terminal to the right at 3:20. BAT is just above it to the left. Chances of yours and what I've got being the same............
Don't hold your breath.

Really need to look at the switch plastic connector (plug-in) in your car and see if the wires are there and if the switch even has a terminal for them if they are. Your manual says yes and the wiring diagram says there is, but you wont know for sure till you look.

[64 Bonnie Ragtop]

Lee and Quick,

GREAT explanation from both of you...THANKS for the clarification! Looking at the back of my spare switch, I believe that the ground terminal is like the one Quik has....where the green wires attach to the terminal positioned at 3:20...below and to the right of the terminal marked BAT.

I probably will not be able to conduct further testing until later this week, but I feel that both of you have given me the info that I need to further diagnose the problem. Ya know, I could easily replace the switch, but then I would be missing out on the fun of diagnosing and learning something new. I'll keep you posted, and I TRULY appreciate both of you for your time and sharing your expertise.

Vince

[64 Bonnie Ragtop]

PROBLEM RESOLVED!

Quick, Lee, and Steve,

Thanks for your suggestions. I installed a new ignition switch, and the "HOT" light now comes on when the ignition is in the START position. I did some diagnosing along the way: Before I installed the new switch, I clipped a lead on one of the hot terminals at the fuse box, and held the new switch against a grounded portion under the dash. With a screwdriver, I turned the switch to the START position, and touched the ground terminal with the other end of my test light.....the test light lit. When I conducted the same test with the switch that I just removed, the test light did not come on. So, everything worked with the "old" switch, except internally, the ground terminal was not making ground contact (as you suggested) when the switch was in the START position.

Thanks, again for your help.

Vince

["QUICK-SILVER"]

Glad you got it fixed. Threads like this are great, where communication is good and something actually gets done.

Funny thing about the switch though, the contact that sees the least amount of work being the one to fail.