Starting Issues when hot
Thread Starter
Cruising
Joined: Jul 2023
Posts: 12
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Starting Issues when hot
1965 C2 Conv 350 HP - Have a new battery, alternator and now a new starter. Charge battery over night car starts easily in the morning. Start car, turn on light and radio and let idle for 30 min / engine temp is 180 to 200. After awhile radio stops working and only works when I rev engine. Turn car off and immediately try to restart and starter drags and sounds like a low charged battery. Had battery tested and they said low charge. Read some other forums and others were talking about heat sink. Cables appear to be fine and heavy duty. We tried to put a quick charge on and also a booster and car would not start until I charged over night. I am a new classic car owner and not a mechanic so I am at a loss. Does this sound like a faulty Battery, Alternator, Starter, Heat Sink? Can’t get in the classic car repair center for 8 weeks!!! Any ideas on how best to test and figure this out? Original motor, trans and no electrical changes before the problem started…
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,073
Likes: 4,206
From: US-PNW
Do other electrical components fail as the car heats up? If not, you may have two separate issues, though the radio coming back to life while revving seems alternator/regulator connected. Heat sink in the starter can certainly cause higher resistance to cranking but I think a test of the charging system is in order prior to looking at that. (Do you have stock exhaust or aftermarket headers?)
Get yourself a digital multi-meter to test electrical components. They are pretty inexpensive - most $30-$60 -- but you can splurge higher for more bells and whistles. Make sure the meter has DC volts, amps, continuity, and ohms. (I doubt a meter is out there without these, but I don't know that for sure.) Innova, Fluke, and Klein are reputable brand names.
Testing the charging system is easy to do and will help isolate any issues. I'll let others describe how to do that but a thread search will yield a huge amount of method instruction.
Get yourself a digital multi-meter to test electrical components. They are pretty inexpensive - most $30-$60 -- but you can splurge higher for more bells and whistles. Make sure the meter has DC volts, amps, continuity, and ohms. (I doubt a meter is out there without these, but I don't know that for sure.) Innova, Fluke, and Klein are reputable brand names.
Testing the charging system is easy to do and will help isolate any issues. I'll let others describe how to do that but a thread search will yield a huge amount of method instruction.
Thread Starter
Cruising
Joined: Jul 2023
Posts: 12
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Starting issues when hot
Thank you for your advice. I’ll test the charging system. Alternator was replaced about 30 days ago; it may be bad.
Yes original exhaust system.
No updates to any other electrical systems or accessories in the past 12 months. Just the new battery, alternator and starter.
It sounded like alternator to me but since it was so new and reading about heat sink on other posts, I realized I don’t know what I don’t know.
I haven’t had a heat sink issue since I purchased the car; however, we are having extremely hot days here in Texas.
thank you
Yes original exhaust system.
No updates to any other electrical systems or accessories in the past 12 months. Just the new battery, alternator and starter.
It sounded like alternator to me but since it was so new and reading about heat sink on other posts, I realized I don’t know what I don’t know.
I haven’t had a heat sink issue since I purchased the car; however, we are having extremely hot days here in Texas.
thank you
Le Mans Master
Joined: Jan 2007
Posts: 5,995
Likes: 1,502
From: Prescott Arizona
Cmax - Welcome to the Corvette Forum. Post up some pics of your new-to-you 65 L79, love to see it.
As 67:72 mentioned, pick up a good Volt-Ohmeter and read up on it's usage. When you get one and can post some numbers for us, like battery voltage (engine off),
and running voltage will help us try to figure out if it's a connection problem or one of the components. Woudln't be the first time that a supposed 'new' part was not up to snuff.
By the way, when all this is going on, what does the dash Battery Gauge indicate?
Mike T - Prescott AZ
As 67:72 mentioned, pick up a good Volt-Ohmeter and read up on it's usage. When you get one and can post some numbers for us, like battery voltage (engine off),
and running voltage will help us try to figure out if it's a connection problem or one of the components. Woudln't be the first time that a supposed 'new' part was not up to snuff.
By the way, when all this is going on, what does the dash Battery Gauge indicate?
Mike T - Prescott AZ
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,073
Likes: 4,206
From: US-PNW
Just had another thought: disconnect the hot wire at the battery**, then crawl under the car and check the starter connections for cleanliness and snug nuts. While there, give the ground cable to the engine a bit of a snug too. Make sure the alternator main wire nut is tight and the plug-in is seated -- same for the regulator on the firewall by the alternator. Checking connections should always be the first part of any electrical diagnosis.
Being that it's a new alternator, start there. Was this problem what caused the alternator replacement?
Set the meter to DC Volts, hold the meter's leads to the battery terminals (black=negative, red=positive). If the battery has removable caps, make sure the electrolyte level is just to the split ring level, about 1" below overflowing. Only fill with distilled water if needed.
Being that it's a new alternator, start there. Was this problem what caused the alternator replacement?
Set the meter to DC Volts, hold the meter's leads to the battery terminals (black=negative, red=positive). If the battery has removable caps, make sure the electrolyte level is just to the split ring level, about 1" below overflowing. Only fill with distilled water if needed.
- With the engine off, the voltage should be 12.5v, +/- a few tenths.
- With the engine running, the voltage should be 13.8v to 14.4v, again, +/- a few tenths.
- Test the direct output of the alternator by touching the black to the frame and the red to the main large wire terminal on the alternator (under the protective boot). The voltage here should be nearly identical to the running battery reading. If not then there's an issue with the charging wiring to the battery.
Last edited by barkingrats; Jul 24, 2023 at 02:53 PM.
Thread Starter
Cruising
Joined: Jul 2023
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To answer your question Safety Car, sudden failure to start triggered trip to Auto Parts shop and had starter, battery & alternator tested. Was told starter was bad so replaced the starter a couple of days ago. The battery was replaced in November and the alternator was replaced in June and now again today. Wires on all three are tight. Will work on getting the reading tomorrow.
This just started happening all the sudden. Today when they retested the alternator they couldn’t get a reading saying good or bad…very strange. The tester usually has a diagnosis in less than a minute. We waited for close to 5 min and no determination. So, we replaced it. Could the regulator be the issue or the heat here causing the problem?
Note: it is very hot here in Houston Texas averaging around 97. Car is running around 180 to 200 degrees.
This just started happening all the sudden. Today when they retested the alternator they couldn’t get a reading saying good or bad…very strange. The tester usually has a diagnosis in less than a minute. We waited for close to 5 min and no determination. So, we replaced it. Could the regulator be the issue or the heat here causing the problem?
Note: it is very hot here in Houston Texas averaging around 97. Car is running around 180 to 200 degrees.
Thread Starter
Cruising
Joined: Jul 2023
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I will post some pics after this weekend assuming I can make it to the Cars and Coffee event with this one. May have to take the wife’s and daughters car instead…was hoping to take all three. Will see!
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,404
From: Redacted
Cmax.....this experience may or may not help fix your problem, but I thought it at least relevant to your issue....
I have an LS swapped 1972 C20 Suburban I use as a daily driver. When we moved to Austin two summers ago, I was having issues with the truck starting normally in the morning but if it was later in the afternoon with the temperature over 100 and I stopped to go to the store, or pick up the kids, the truck would not start again until it had significant time to cool down....sometimes multiple hours depending on the temp. I could hear the click of the starter, but it just wouldn't start.
I tried a new starter, multiple solenoids, read wires, tried a different battery and nothing solved the issue. At cars and coffee one morning, I described my issue to another local guy who daily drives an 80 series LandCruiser. He told me that he had been having the same issue and that his problem had been that the wire, running from the ignition switch to the starter solenoid was of a small enough gauge (from the factory) that when the wiring would get hot in the engine bay, causing the resistance in the wire to increase slightly, it would be enough to prevent the solenoid from seeing sufficient amperage to turn the motor over. His solution was to use the ignition wire to trigger a relay sending power directly from the battery to the solenoid.
Just to test the idea, I bought one of those 4 AWG jumper cables with the fused button that you can hook up from the battery to the solenoid to essentially "hot wire" the car from the outside.
https://www.summitracing.com/parts/oes-25331
I then drove the truck for the next week and sure enough, any time it wouldn't start, Id attach the two leads to the battery and the solenoid, turn the key to RUN, hit the botton, and it would fire right up.
Following suit, I ordered a Kaizen Speed solid state relay and 20 feet of 10 AWG TXL wire, using the purple ignition wire in the Painless Wiring harness to trigger the relay. Sure enough, the truck turns over quicker and starts faster, regardless of temperature, or how heat soaked it may be.
Hope that helps!
I have an LS swapped 1972 C20 Suburban I use as a daily driver. When we moved to Austin two summers ago, I was having issues with the truck starting normally in the morning but if it was later in the afternoon with the temperature over 100 and I stopped to go to the store, or pick up the kids, the truck would not start again until it had significant time to cool down....sometimes multiple hours depending on the temp. I could hear the click of the starter, but it just wouldn't start.
I tried a new starter, multiple solenoids, read wires, tried a different battery and nothing solved the issue. At cars and coffee one morning, I described my issue to another local guy who daily drives an 80 series LandCruiser. He told me that he had been having the same issue and that his problem had been that the wire, running from the ignition switch to the starter solenoid was of a small enough gauge (from the factory) that when the wiring would get hot in the engine bay, causing the resistance in the wire to increase slightly, it would be enough to prevent the solenoid from seeing sufficient amperage to turn the motor over. His solution was to use the ignition wire to trigger a relay sending power directly from the battery to the solenoid.
Just to test the idea, I bought one of those 4 AWG jumper cables with the fused button that you can hook up from the battery to the solenoid to essentially "hot wire" the car from the outside.
https://www.summitracing.com/parts/oes-25331
I then drove the truck for the next week and sure enough, any time it wouldn't start, Id attach the two leads to the battery and the solenoid, turn the key to RUN, hit the botton, and it would fire right up.
Following suit, I ordered a Kaizen Speed solid state relay and 20 feet of 10 AWG TXL wire, using the purple ignition wire in the Painless Wiring harness to trigger the relay. Sure enough, the truck turns over quicker and starts faster, regardless of temperature, or how heat soaked it may be.
Hope that helps!
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Le Mans Master
Joined: Sep 2008
Posts: 5,662
Likes: 2,344
From: Lake Minnetonka, Mn
2018 C1 of Year Finalist
Cmax.....this experience may or may not help fix your problem, but I thought it at least relevant to your issue....
I have an LS swapped 1972 C20 Suburban I use as a daily driver. When we moved to Austin two summers ago, I was having issues with the truck starting normally in the morning but if it was later in the afternoon with the temperature over 100 and I stopped to go to the store, or pick up the kids, the truck would not start again until it had significant time to cool down....sometimes multiple hours depending on the temp. I could hear the click of the starter, but it just wouldn't start.
I tried a new starter, multiple solenoids, read wires, tried a different battery and nothing solved the issue. At cars and coffee one morning, I described my issue to another local guy who daily drives an 80 series LandCruiser. He told me that he had been having the same issue and that his problem had been that the wire, running from the ignition switch to the starter solenoid was of a small enough gauge (from the factory) that when the wiring would get hot in the engine bay, causing the resistance in the wire to increase slightly, it would be enough to prevent the solenoid from seeing sufficient amperage to turn the motor over. His solution was to use the ignition wire to trigger a relay sending power directly from the battery to the solenoid.
Just to test the idea, I bought one of those 4 AWG jumper cables with the fused button that you can hook up from the battery to the solenoid to essentially "hot wire" the car from the outside.
https://www.summitracing.com/parts/oes-25331
I then drove the truck for the next week and sure enough, any time it wouldn't start, Id attach the two leads to the battery and the solenoid, turn the key to RUN, hit the botton, and it would fire right up.
Following suit, I ordered a Kaizen Speed solid state relay and 20 feet of 10 AWG TXL wire, using the purple ignition wire in the Painless Wiring harness to trigger the relay. Sure enough, the truck turns over quicker and starts faster, regardless of temperature, or how heat soaked it may be.
Hope that helps!
I have an LS swapped 1972 C20 Suburban I use as a daily driver. When we moved to Austin two summers ago, I was having issues with the truck starting normally in the morning but if it was later in the afternoon with the temperature over 100 and I stopped to go to the store, or pick up the kids, the truck would not start again until it had significant time to cool down....sometimes multiple hours depending on the temp. I could hear the click of the starter, but it just wouldn't start.
I tried a new starter, multiple solenoids, read wires, tried a different battery and nothing solved the issue. At cars and coffee one morning, I described my issue to another local guy who daily drives an 80 series LandCruiser. He told me that he had been having the same issue and that his problem had been that the wire, running from the ignition switch to the starter solenoid was of a small enough gauge (from the factory) that when the wiring would get hot in the engine bay, causing the resistance in the wire to increase slightly, it would be enough to prevent the solenoid from seeing sufficient amperage to turn the motor over. His solution was to use the ignition wire to trigger a relay sending power directly from the battery to the solenoid.
Just to test the idea, I bought one of those 4 AWG jumper cables with the fused button that you can hook up from the battery to the solenoid to essentially "hot wire" the car from the outside.
https://www.summitracing.com/parts/oes-25331
I then drove the truck for the next week and sure enough, any time it wouldn't start, Id attach the two leads to the battery and the solenoid, turn the key to RUN, hit the botton, and it would fire right up.
Following suit, I ordered a Kaizen Speed solid state relay and 20 feet of 10 AWG TXL wire, using the purple ignition wire in the Painless Wiring harness to trigger the relay. Sure enough, the truck turns over quicker and starts faster, regardless of temperature, or how heat soaked it may be.
Hope that helps!
Race Director
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From: San Antonio, TX/Mahopac, NY
2024 Corvette of the Year Finalist - Modified
2024 Corvette of the Year Finalist - Unmodified
2023 C7 of the Year Winner - Modified
Sounds like a bad regulator to me. Measure the battery voltage with the engine off. Should be around 12.8v. Start the car and measure it again. Should be between 12.8 and 14.5v. If it never goes above 12.8v and slowly drops below then the alternator is not charging the battery which sounds like a regulator problem to me. There are many YouTube videos on testing the VR. Good luck!
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,404
From: Redacted
Thought about it, but given the fact that the standard solution for high draw accessories like electric fans and fuel pumps is a relay, I figured that was probably the solution with the highest likelyhood of success. And with these new solid state relays hitting the market, you dont have to worry about them failing as there are no mechanical components.
Thread Starter
Cruising
Joined: Jul 2023
Posts: 12
Likes: 1
Pre start (engine off). Battery 12.59. Alternator 12:05
Car running tests: Battery 13.78. Alternator 14.15, 13.89, 13.68,
Car temp at 180 degrees. Battery 13.49. Alternator 13.6, 13.55
Car off and electric fan cycle: Battery 12.08. Alternator 12.13. (Fan cycles on and off until temp is below thermostats.
Car off & no more fan cycles: Battery 12.18. Alternator Alternator 12.2
***So the electric fan has been on car since I purchased it last year and has not ever drawn battery to a point of not starting easily.
Tried to start it after car cooled off and still slow turning starter. So, I hooked up the battery booster (set on 55 amps) and it started right up. Leading me to believe the battery isn’t getting enough juice to stay charged enough to start after driving it for awhile.
Dan has the theory of it being a weak wire to starter and when hot the problem rears its ugly head. Because the numbers move they way they do, like Factoid I think it could be the regulator.
Does this sound like the regulator is failing. It appears to be to be the original Delco Remy unmolested.
Car running tests: Battery 13.78. Alternator 14.15, 13.89, 13.68,
Car temp at 180 degrees. Battery 13.49. Alternator 13.6, 13.55
Car off and electric fan cycle: Battery 12.08. Alternator 12.13. (Fan cycles on and off until temp is below thermostats.
Car off & no more fan cycles: Battery 12.18. Alternator Alternator 12.2
***So the electric fan has been on car since I purchased it last year and has not ever drawn battery to a point of not starting easily.
Tried to start it after car cooled off and still slow turning starter. So, I hooked up the battery booster (set on 55 amps) and it started right up. Leading me to believe the battery isn’t getting enough juice to stay charged enough to start after driving it for awhile.
Dan has the theory of it being a weak wire to starter and when hot the problem rears its ugly head. Because the numbers move they way they do, like Factoid I think it could be the regulator.
Does this sound like the regulator is failing. It appears to be to be the original Delco Remy unmolested.
Last edited by Cmaxwell1964; Jul 25, 2023 at 08:45 PM.
Thread Starter
Cruising
Joined: Jul 2023
Posts: 12
Likes: 1
I do not think so…
I can disconnect it and run same tests tomorrow.
Tried to start it after car cooled off and still slow turning starter. So, I hooked up the battery booster (set on 55 amps) and it started right up. Leading me to believe the battery isn’t getting enough juice to stay charged enough to start after driving it for awhile. Does this sound like the regulator is failing. It appears to be to be the original Delco Remy unmolested.
I can disconnect it and run same tests tomorrow.
Tried to start it after car cooled off and still slow turning starter. So, I hooked up the battery booster (set on 55 amps) and it started right up. Leading me to believe the battery isn’t getting enough juice to stay charged enough to start after driving it for awhile. Does this sound like the regulator is failing. It appears to be to be the original Delco Remy unmolested.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,073
Likes: 4,206
From: US-PNW
Pre start (engine off). Battery 12.59. Alternator 12:05
Car running tests: Battery 13.78. Alternator 14.15, 13.89, 13.68,
Car temp at 180 degrees. Battery 13.49. Alternator 13.6, 13.55
Car off and electric fan cycle: Battery 12.08. Alternator 12.13. (Fan cycles on and off until temp is below thermostats.
Car off & no more fan cycles: Battery 12.18. Alternator Alternator 12.2
Does this sound like the regulator is failing. It appears to be to be the original Delco Remy unmolested.
Car running tests: Battery 13.78. Alternator 14.15, 13.89, 13.68,
Car temp at 180 degrees. Battery 13.49. Alternator 13.6, 13.55
Car off and electric fan cycle: Battery 12.08. Alternator 12.13. (Fan cycles on and off until temp is below thermostats.
Car off & no more fan cycles: Battery 12.18. Alternator Alternator 12.2
Does this sound like the regulator is failing. It appears to be to be the original Delco Remy unmolested.
Thread Starter
Cruising
Joined: Jul 2023
Posts: 12
Likes: 1
The regulator is the original and followed the testing recommendations suggested. (67:72). The unit tested out fine and putting out over 14. So, I disconnected the fan and drove the car for 10 to 20 minutes, pulled in the garage and turned off and tried to restart. SUCCESS!!! The issues seems to have something to do with the aftermarket electric fan it seems.
So I monitored the temps with and without the electric fan while driving. (Not sitting idle for longer than a light or so) The driving temp with the fan is spot on 180. Without the fan, the driving temp ranges from just a hair above 180 to about 200. Never more than half way between 180 and 220. Given the extreme temp this time of year ranging around 100 degrees and with these latest temp results with and without fan, I am not sure I really need it unless planning on sitting idle for an extended amount of time.
The fan is currently wired directly to the headlight junction box under the dash giving it direct power from the battery. I am thinking because the fan is running after car is off and pulling power, the car doesn’t have the amps to run fan and start the car while running. So, I have two questions…
1. What should be the normal operating temp of the water while driving on the hot summer days? (180 - 210)
2. Do I really need this fan and if so, wouldn’t it make sense to wire it to accessories so that it didn’t run after car was turned off? (Remember fan has its on thermostat and only runs while car is above whatever the setting is…
UPDATE TO THIS POST: One hour later, would not start. Same slow turning of motor. Fan is still disconnected…
So confused…
So I monitored the temps with and without the electric fan while driving. (Not sitting idle for longer than a light or so) The driving temp with the fan is spot on 180. Without the fan, the driving temp ranges from just a hair above 180 to about 200. Never more than half way between 180 and 220. Given the extreme temp this time of year ranging around 100 degrees and with these latest temp results with and without fan, I am not sure I really need it unless planning on sitting idle for an extended amount of time.
The fan is currently wired directly to the headlight junction box under the dash giving it direct power from the battery. I am thinking because the fan is running after car is off and pulling power, the car doesn’t have the amps to run fan and start the car while running. So, I have two questions…
1. What should be the normal operating temp of the water while driving on the hot summer days? (180 - 210)
2. Do I really need this fan and if so, wouldn’t it make sense to wire it to accessories so that it didn’t run after car was turned off? (Remember fan has its on thermostat and only runs while car is above whatever the setting is…
UPDATE TO THIS POST: One hour later, would not start. Same slow turning of motor. Fan is still disconnected…
So confused…
Last edited by Cmaxwell1964; Jul 26, 2023 at 12:32 PM.
Instructor
Joined: Nov 2021
Posts: 146
Likes: 43
From: Summerville, SC
I would like to confirm a few things as I have some suspicions. What is the rated output of your alternator at idle (usually listed as its IL rating)? I ask this as one symptom is that during idle after a while, you will lose your radio unless you rev it, which tells me that during idle, your alternator cannot support your fan and accessories which is leading to battery drain (you would be surprised how much an electric fan can take to operate) On that note, check the amperage draw of your fan at different speeds (if it supports multiple speeds); you can usually check both these things by inputting the model number of your part and doing a search, of course you could use a clamp meter for the draw as well. Next, I would definitely ad a relay to your fan so that it cuts off with your ignition. Finally, you imply that your fan is wired in with the headlight junction box. Is the fan on its own dedicated power circuit back to the battery and not sharing the line with another item, I would make sure that fan has its own line back to the battery to include a fuse.