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  #1  
Old 5 Days Ago
iiAtlas iiAtlas is offline
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Default SIII Water Temp Sender/Guage Troubles

Hello All!

Here for my annual check up.. I am on the hunt to sort out my overheating issues..or what I thought were overheating issues.

Cruising around town I could go 5-10 minutes before my water temp gauge read 230 degrees. At idle, the gauge would rapidly decrease to a steady 170 degrees. Then when we got moving again, it would shoot up to 200+. Back to stopped at idle, back down to 170. Eventually after ~20 minutes the car would shut down completely. I had assumed I had overheated and waited some time to let the car cool.

This is as far as I had diagnosed the car for the past ~1 year. Crazy, I know. I was working on other projects and didn't have the gusto to dive in. The sunbeam is my favorite car, I just love her to death. Anyways..I poked around and it was obvious what the problem was. The car was developing vapor lock. The fuel line runs directly overtop the engine block over to the exhaust manifold. I have sheathed the lines with "hot rod sleeve" a 1100 degree heat shield until I can re-plumb the hard lines to the other side of the engine bay. I am hoping this will sort that issue. I also replaced the upper and lower radiator hoses, just in time it would seem as one had a crack and would've blown at any minute.



Next up was the water temp sender/gauge. Either one of these had to be wrong I imagined as the readings I was getting were just inane, irrelevent. The car temp was nowhere near 200 when it was reading 230+, it had just started! The temps couldn't possible drop from 230 to 150 as quickly as they were (seconds). I was convinced either the temp sender was wrong, the gauge was wrong, or the wiring was wrong. My previous presumed overheating was actually just vapor lock.

I attempted to diagnose the temp sender by putting it in boiling water and pulling a resistance reading off of it. This is a new sending unit. I must've done something wrong as I just got a random stream of numbers. Totally random. I put one probe on the body and one on the top terminal. I tried grounding the sender to the block too, all random. I must be doing something wrong.

At this point I dove into the wiring. I had a new black wire which went directly from the sender to the instrument voltage regulator. This is..wrong? At least according to the diagram. I then had another wire running directly off the instrument to the...coil!? Why?? This made no sense to me. I began to become convinced this was hooked up wrong. I turned the car back on and inspected. As I pressed on the accelerator, the water temperature gauge shot up, as I eased off it went back down. Almost a 1:1 reading. The gauge must be just pulling a voltage reading off the voltage regulator, which changes based on RPM, and have absolutely no bearing on the actual water temp?

I rewired it as follows: temp sender directly too temp gauge left post, right post to voltage regulator. Now I get no reading at all. The voltage regulator also runs the fuel gauge, and from what I can tell that is operating properly.

Here how I have it wired up now:









Any help would be greatly appreciated!! I am stumped

PS: By thermo bulb do they mean the temp sending unit? They use the word lamp, light, and bulb all over the place...not sure if this bulb is meant to be the sending unit or an actual bulb. If it is a bulb, where does the gauge get it's signal from?

THANK YOU ALL !!
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Old 5 Days Ago
iiAtlas iiAtlas is offline
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Here is how the gauge used to be wired for comparison:





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Old 5 Days Ago
loose_electron loose_electron is offline
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First things first - You either should have or should get an infrared thermometer so you can get accurate temperatures off the engine block and the radiator. $12-15 on EBay.

The older cars used a bridge circuit and the newer cars used a voltage regulator and voltage divider. In either case two things that need to be checked is that you have some resistance across the temp sensor, and what the voltage coming out of the voltage regulator is.

The temp sensor should not be an open circuit, I would expect something in the 20-500 ohm range and I am sure someone else can give a much more accurate number. I've gone over to a V6, Pete's wiring harness and Speedhut gauges, so I don't have specifics for the original setup.
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  #4  
Old 5 Days Ago
Ken Ellis's Avatar
Ken Ellis Ken Ellis is offline
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Check out post 6 in this thread:
http://www.sunbeamalpine.org/forum/s...nce#post169989

And for general educational reading, do an advanced search with the keywords: "sender resistance" from poster "Tom H" ... all without the quotes.

Bad ground on the instrument regulator could be an issue... what is that white bare-ended wire in the pics? I believe the reg. is usually grounded thru its mounting screw? (Not a S3 owner.)

Also, generator or alternator? Positive or negative ground? (Shouldn't matter to the operation though...)
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Old 5 Days Ago
iiAtlas iiAtlas is offline
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Quote:
Originally Posted by Ken Ellis View Post
Check out post 6 in this thread:
http://www.sunbeamalpine.org/forum/s...nce#post169989

And for general educational reading, do an advanced search with the keywords: "sender resistance" from poster "Tom H" ... all without the quotes.

Bad ground on the instrument regulator could be an issue... what is that white bare-ended wire in the pics? I believe the reg. is usually grounded thru its mounting screw? (Not a S3 owner.)

Also, generator or alternator? Positive or negative ground? (Shouldn't matter to the operation though...)
Quote:
Originally Posted by loose_electron View Post
First things first - You either should have or should get an infrared thermometer so you can get accurate temperatures off the engine block and the radiator. $12-15 on EBay.

The older cars used a bridge circuit and the newer cars used a voltage regulator and voltage divider. In either case two things that need to be checked is that you have some resistance across the temp sensor, and what the voltage coming out of the voltage regulator is.

The temp sensor should not be an open circuit, I would expect something in the 20-500 ohm range and I am sure someone else can give a much more accurate number. I've gone over to a V6, Pete's wiring harness and Speedhut gauges, so I don't have specifics for the original setup.
Thank you both for your replies! loose_electron I DO have one of those infrared thermometers and love it! Great tool. I also used a kitchen thermometer in the radiator to pull a reading. Temps all looking good in the 160 degree range, as that is the thermostat I am running.

Ken, thank you for the links I tried search but couldn't find anything, I must've been using the tool wrong. My sender gives me no meaningful resistance figure so I will assume it is bad. You are correct, the ground is on the back of the case. A ground wire daisy chains its way along the back of the fuel gauge, water temp gauge, speedo, oil gauge, etc. Now the fact that I get some reading when I hook the gauge up like it used to be (direct to coil) means in theory I should be getting a fine ground, correct?

Any way to test the voltage off the voltage regulator? Thank you both!
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  #6  
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Tom H Tom H is offline
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Atlas, very simple fist step. :

1) disconnect the lead from the temp sender/ sensor/ bulb. And measure the voltage. Best to measure with an analog (moving needle) meter, or just a test lamp. If it's a factory original type regulator (they call it a stabilizer to keep from being confused with the main battery system regulator) , it should switch between full battery voltage to zero about 2 times per second.

Let me know what you find

Tom

Better yet, e-mail to me your phone #, I'll call you. To send an e-mail click on my name and chose "send an e-mail"

Last edited by Tom H : 5 Days Ago at 06:22 PM.
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Old 5 Days Ago
loose_electron loose_electron is offline
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Quote:
Originally Posted by iiAtlas View Post
Any way to test the voltage off the voltage regulator? Thank you both!
A voltmeter (digital multimeter) should get it done.

If my memory is correct the voltage regulator was set for 10 volts.

If you got an open circuit from the temp sensor I would start there.
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iiAtlas iiAtlas is offline
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Quote:
Originally Posted by Tom H View Post
Atlas, very simple fist step. :

1) disconnect the lead from the temp sender/ sensor/ bulb. And measure the voltage. Best to measure with an analog (moving needle) meter, or just a test lamp. If it's a factory original type regulator (they call it a stabilizer to keep from being confused with the main battery system regulator) , it should switch between full battery voltage to zero about 2 times per second.

Let me know what you find

Tom

Better yet, e-mail to me your phone #, I'll call you. To send an e-mail click on my name and chose "send an e-mail"
Thank you Tom! Just sent you an email..you rock! To confirm the above..disconnect lead from sender to regulator, then with battery on (and car running?) test voltage?

Quote:
Originally Posted by loose_electron View Post
A voltmeter (digital multimeter) should get it done.

If my memory is correct the voltage regulator was set for 10 volts.

If you got an open circuit from the temp sensor I would start there.
Thank you loose_electron!
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Old 5 Days Ago
Tom H Tom H is offline
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Loose, The problem with using a digital multimeter, is, assuming it's an original type stabilizer, is that it operates on an On/Off principle at about 2 per second, to achieve avg 10 V. This ends up reading as total random readings on a Digital.

Altas, I found your e-mail in my Junk. I'll call in a few minutes


Tom
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  #10  
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Tom H Tom H is offline
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Just a f/u for those following. Atlas tested the circuit as I described, using a test lamp, and found the voltage would flash between full and zero about 2 times per sec. So there is voltage and the regulator/ stabilizer works. Measured the resistance of the sender and it reads infinite on the 20,000 ohm range on his Digital Meter. So looks like a bad sender. And his temp gauge read full scale when he hooked up the test lamp. The test lamp simulates a sender in Low resistance ( High Temperature) state, so that further confirms that the circuit works.

Interesting note: Atlas is a young guy and must be among the youngest forum member. Great to have young folk here enjoying Sunbeams!!!

Tom
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