Temerature idiot light on

Before putting my Star Chief away for the winter the hot light on the dash has started coming on and staying on when I first start the car. It stays on until the engine heats up a little then goes off.
I assume it was probably the temp sensor on the engine and change it out but it still does the same thing. Any thoughts on what might be causing this reaction?

Thanks

wydtrac.....This is how it works. There is 12 volt + going to the green warning lamp. the path to ground goes through the ignition "run" position and then to the temperature sensor on the intake manifold. When the engine is cold, the circut is completed when you turn the key on. The light stays on until the coolant becomes warm enough that the ground is broken by the sensor. The red "hot" lamp works the same way except that the ground path to it is completed if the coolant overheats. Should the lamp burn out you would not know you had trouble. When you turn the ignition to the "start" position, a direct path to ground is completed bypassing the sensor. The red lamp lights as a ckeck of the bulb. If your lamp stays on for a short time after you release the key from "start" it could mean that your ignition switch is slow to spring back to the "run" position. It could also mean that there is a temporary short in the ground path that disappears once the engine begins to warm up. Let me know if you need me to ckeck the wiring diagram for the wire colors you should test.
I forgot that you had a Starchief. We need some information for a project we are doing. Does your car have a clock? Also does it have the assist bar on the passenger side of the dash like the Bonnevilles do?.....John

John, My Star Chief does indeed have a clock, although it is stopped at 5 o'clock (it's 5 o'clock somewhere!) and not working.
The assist bar it does not have. At least I dont think it does. I am not familiar with the assist bar in the Bonneville. I have attached pictures of mine.
Thanks for the detailed description of the operation of the temp sensor lights. I will check the ignition switch for sticking and maybe the ground to the light itself. The green cold light does not come on at all. The red hot light comes on cold and goes off when the engine warms a little. Sounds like a ground issue I think.
Thanks again.

I wonder : could it be that the 'hot' lamp wire is accidentially connected to the 'cold' terminal of the sensor. It is a dual function thermostatic sensor, and both connectors are grounded - one when the engine is cold, and one when it is hot. In case they are swapped, the hot light will act as the cold light (light up cold, then come of as the engine warms up a little), and vice versa. I would check the lights, just by grounding one wire at the time (disconected from the sensor, and hold to ground), and check that the lights come on. If the hot light does not work at all, then it may just be the bulb that has failed....

Good suggestion. I will check it as you say, however, the hot light coming on cold started out of the blue one day. I had not done anything to the sensor at that time. I was not sure when I replaced the sensor which connector went where, so it could be as you descibed. With my luck the connectors are backwards.
Thanks

wydtrac.....The cold lamp wire is light green, the hot lamp is dark green. They should both terminate in an "L" shaped connector at the sender. These are your grounds. The 12 volts comes to the lamps through purple wires from the ignition switch. Another thought, could you have the hot lamp socket plugged in behind the cold lens, and vice versa?,.....John

P.S. Thanks for the pictures. That answers my question. The Bonneville dash trim is just like yours except they have a padded assist bar on the left side where you have the Starchief script.

Dang John, you're good!

As soon as I read your your idea of the bulbs being switched I remembered how this all came about.
One day this summer when I got in and started the car I noticed a light from beneath the dash. I was on my way somewhere and had no time but reached under and found the hanging bulb and quickly plugged it in the first empty hole I found. It happened to be the hot light socket as I recall. That seems to be when this whole thing started with the hot light on when the engine was cold. I pretty much ignored it till now.

I just went out and climbed under the dash and could see the color of the wires going to the hot and cold and indeed they were backwards. However, I also found that the oil temp light was hanging loose. I proceeded to put the bulbs back in the correct sockets but as I was doing the oil light I must have done something because as I was pulling on the wires the bulb went out and now it wont go back on. None of them will. I figured I blew a fuse but all fuses are testing good. I dont know what I did but now I have a new problem. This kind of !@#$%^%& follows me around. I can't touch anything without friggin' up something else in the process.
Oh well, tomorrows another day. Maybe I can figure this one out then.

Thanks all for your help with this one. I really appreciate it.

wydtrac.....I know what you mean. Sometimes it seems that everything I touch, turns to crap. On those days I look at my toolbox and think; I should weld the drawers shut, and have a professional do it!

It now looks like you have a voltage supply problem. Just follow the purple wire of any one of those lamps. They all join together and end at the ignition switch. Thats where they get their power. Real pain laying on your back, legs up over the seat, and flashlight in your mouth. As Bernie Parent would say, "some fun eh.".....John

I see by your description, upside down under the dash, that you have been there, done that.
I found my source of the noise I heard. A red wire (hot) arched against a ground. I figured it blew a fuse but it didn't. It blew a bulb, and then another, before I could tape it over. Turns out it is the hot wire to the clock. No wonder it didn't work. But, I plugged it in and it still doesn't work. Which made me think why not take it out and get it fixed. Big mistake! I couldn't get the two nuts off the back of it to remove it so I began taking things out to get to it. Ash tray, radio, hot air hoses, glove box. Crap! still can't get it out. I'm going to regret this, I just know it.

wydtrac.....I've got a couple instrument clusters out in the shed. When I did mine I had the cluster out so it was easy, but I forget how the clock comes apart. I'll check one of them and get back to you. Whatever you do, don't take the heater control out! It's a real pain to get back in from under the dash. When I took mine out, I wanted to convert it to quartz. I called one of the companies that advertise kits to do it yourself. They told me that that particular clock had to be done by them, because the kit had to be modified. I sent it to them and it cost around $120. When it came back to me, it was a rather shoddy job. I took it apart and put it back together the right way. It's worked well ever since. Had the same experience with my Firebird with a General Time clock: "you can't do that one yourself." Called another company and told them I had a Camaro with a Borg clock, and they sent me a kit. It wasn't a difficult job, and made for a nice winter project. About $35 for the kit......John

It definately would be easier if the entire cluster was out of the dash, but I have given up on it. I got so I could get to the two nuts on the back of the clock that hold it in. The manual says take those two nuts off and the clock comes out from the front. Easy enough. But I can't seem to free up the nuts on the back of it. When I turn them the entire nut and bolt both turn and I get nowhere. I even tried holding the bolt with needle nose vice grips but was afraid I would break something. Oh well, it wasn't that big a deal. Most clocks in a car this age don't work anyway. It did give me a chance to clean out all that nasty insulation that keeps falling on my feet! And I took the radio out and cleaned it up too. I only get one station on the radio and that isn't very good. Maybe I need a new antenna? Mine is the type with the spring at the bottom of it. Is that an orginal type or should I find a replacement. I don't really care if the radio work either. I never turn it on in case the car makes a noise I should hear.
Thanks for your help John!

Does anybody know the temps at which the cold light goes off, and the hot light comes on? Just curious. I may dig for the sensor and stick it in a pan on the stove with a candy thermometer.

Also, I'd like to run a separate analog temp guage along with the original cold/hot lights. Is there an orifice in the cooling system that I can safely tap into that won't affect the durability of the cooling system?

As far as the original clocks go, I have read that 9 times out of 10, a good cleaning and oiling of the internals brings them back to perfect operation. Certainly worth a try!

I recommend you use some teflon oil - there are several brands, and it never 'gums up', unlike almost any other lubricant. Also, if possible, remove the scale and hands, and let it soak in a ultrasound cleaner - to remove old lubricants.
My experience with electromechanical pinball mechanisms tells me this works well - i have also used this method on old mechanical (springdriven) clocks with sucess...
I got a clock off e-bay, from someone hwo restores them, and it came with a instruction sheet, that said to install a switch, so that the clock could be turned off during storage - it said that even a 'new condition' clock only has a few years of service in it, so it was a good idea to save it...

59safaricat.....suprisingly, when I looked it up in the Master Parts Catalog, there were two senders listed. One was for air conditioned and 420E equiped cars, with a "hot" temperature of 244*. The other was for all other cars, and was 238*. I would think that replacement senders would be universal. It doesn't mention the "cold" turn off temperature, but it's probably around 80*. On a hot day (85*+) mine doesn't come on at all. There are also two different radiator caps. 13lbs for all cars, and 15lbs for A/C and 420E. These raise the boiling point to 244* and 248* respectively at sea level. Funny, I can understand the higher temperatures for A/C; but why for the 420E?

To use an actual gage, you have three options. First, and probably the easiest, would be to drain a little coolant and replace the original sender with one for a gage. The downside to this is that you lose the cool factor of the red and green lamps. The second option would be to drill and tap the manifold to accept the sender for the gage an inch or two away from the existing sender. To do this though, you need to remove the manifold to prevent metal chips from getting into your coolant passages. You also should know in advance what size to drill and tap it. The third way is a little more work, but is the stealthiest. The engine block has a drain plug on each side down near the oil pan rail. If you remove one of the plugs, and find a gage with a sender the same size as the plug this is a good place to put it. The coolant temperature there is as hot as its going to get, as it has already picked up the most heat from the heads, and is on its way back to the radiator. The only downside is some shopping for the right size sender, but you could also drill and tap this hole larger, if you couldn't find the right size. All three locations will be within a couple degrees. There is one other option that is very expensive. You could convert to a Tri-Power with mechanical linkage. The manifold has a fitting near the original sender that is normally used for the thermal vaccum switch. With mechanical linkage it's not needed. Just think it would only cost $1500 or $1600 to do. LOL......John

"you lose the cool factor of the red and green lamps."

John is right, this is very cool! I have my lights in the correct sockets now and had never seen the green "cold" light before. Very cool!

I think it runs better now too John!

Thanks again, John!

The wagon is all apart (including the engine) and sloooowly undergoing a frame off restoration, so now is the time to experiment. I think I'll take your advise tapping into one of the block drain plug holes and having the machine shop work their magic on getting a sending unit to fit in there, while they carry out other machine work to the block.

Yet another way to do it - you could use a analog sender and then derrive the control signal for the warning lights from the analog signal. This requires a little knowledge of what the sensor puts out, but should be fairly easy to do. If you have some specs on the sender unit let me have a look at it...
Most analog sender units consist of a temperature dependent resistor, which changes the current that flows through the gauge unit. When the temperature changes, the voltage across the sender unit changes accordingly, and that is fairly easy to detect with a simple circuit, and as a bonus you would be able to decide for yourself when the lights should come on or off.

I had similar plans myself - and i want to add a acoustic warning if the engine is hot, or the oil pressure low (a buzzer connected parallel to the lamp(s)). I am working hard on the engine, and i don't want to ruin it again (though the buzzer would not have saved my engine this time)...

I, too had this problem with the lights in the dash. It turned out to be a bad sensor and a shoddy wiring repair by the previous owner, that was causing it to prematurely ground itself. The red light would flicker intermittently regardless of the engine's temp. It freaked me out while driving and pulled over to check to make sure it was not overheating. I do have an issue now with overheating, sometimes it blows out the overflow, but not all the time. It did it the first time the other day since I started driving it (mid-June). It was 35 deg. outside when it happened, but it never did it when it was 90-100 deg. so it's a little baffling. I flushed the system and put in fresh coolant and a new cap. I removed the thermostat when I started driving it initially, I think this may be the cause in cold weather, it is too freer flowing than with a thermostat, so I will put in a new one. The radiator is orignal and appears to be in great condition, with no leaks or missing fins and cool to the touch, but it may need to be boiled out to get any deep seated internal sediment stuck inside. The water pump is a fresh rebuild with a new modern bearing shaft and original impellor, so I don't think this is the problem. Any thoughts or suggestion are welcome, if anyone has any ideas. I've been around cars all my life, but these Pontiacs are a lot different than, say a Small Block Chevy. The cooling system is a totally different animal to a Chevy or F@*d (No, I don't like these!!), with the water ports going into the heads. I am curious what you guys have to say. Chad









P.S. You know why the F@*d emblem is an oval?..............They circled the problem!!!

Chad.....Of coarse I'm partial to Pontiacs, but the more I study them, the more impressed with the engineering that went into them. Those people knew what they were doing! The cooling system of the original V-8's (1955-1959) was known as "reverse cooling." The coldest coolant is what enters the water pump from the lower radiator hose. The hottest part of a running engine is the area around the exhaust valve seats, particularly the 3&5 and 4&6 which are next to each other. The idea of the design was to get the coldest coolant to the hottest area first. The water pump forces the coolant through the two small hoses and elbows into the front of the heads first. It should then drop down into the block through passages at the rear of the head and block. After cooling the block it rises back up into the heads through the passages at the front, and then into the intake manifold, thermostat, and back to the top of the radiator. This is a great system, except for one thing. As I've described it, there is nothing to prevent the coolant from just flowing into the block from the front passages, and not providing enough cool flow to the heads. To address this, the engineers provided coolant distribution tubes in the heads. These are stainless steel tubes that run the length of the head on the inside. This forces most of the coolant to flow to the rear of the head. They are flared on the front end to fill the passage where the coolant enters the head. If you were to remove one of the elbows from the water pump you should see them. These tubes also had small holes drilled in them to "squirt" coolant at the valve seat area. Kind of like those old flat soaker hoses that you rolled out to water the lawn. It's not clear why, but in 1960 they went to the more conventional system of water pump straight into block, block to heads, and then out.
All this is to say that, after you check out the normal system things; water pump, radiator, thermostat, hoses, etc, you might want to make sure these tubes are in good working order. They can get clogged up after fifty years. Good luck, and let us know what you find......John

John- Thanks. I knew about the tubes inside the heads. When I first got the car, I went through everything, including the cooling system. I had the pump rebuilt by my BIL, who owns a company specializing in water pumps and friction surfaces for just about anything with an engine. On the left side of the engine (from the front) I had a freeze/ casting plug develop a pinhole leak behind the motor mount. I managed to replace it with a new one given to me by Joe D'Orio at Old Car Parts in Portland, Or. Not an easy task, but I did it without any leaks. But when I had it out I flushed out the block, since apparently these blocks are known to "collect" sediment around the cylinders. You would be amazed just how much shit come out of there! I stuck a flexible magnet inside and pulled out gobs of rust, sediment and a mysterious looking red sludge, that in California, probably causes cancer or is considered toxic in some way. It seems like everything causes cancer in California for some odd reason! Anyway, I stuck the garden hose in there with a fluted nozzle and flushed all that crap out until it was clean. My mistake was not popping out a plug on the other side! I think what is happening is that this sediment is now "migrating" around clogging up the radiator and the rest of the engine I initally flushed clean! With the kitchen renovation taking most of my time, I have not delved into this yet, but I will soon, since I need a break from swinging a hammer, plumbing, electrical and the rest of what goes into a "dream" kitchen! Just what is a dream kitchen anyway? The ideal dream kitchen, in my opinion is called a restaurant, all you have to do is order, eat and pay, without the clean-up!