Basic starting issue question
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Joined: Nov 2004
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From: Centennial
Basic starting issue question
Hello everyone....I have been chasing a starting issue for awhile now and I have a very quick short question. I remember someone posting awhile back that when you have your headlights on and you try to start the truck, that if they stay strong or if they dim that those are signs of possibly different issues. When I attempt to start mine....the headlights die completely. What would that tell me about the circuit? Any help would be great! Its a '76 F-250 with a 390. 4X4
Nate
Nate
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
The test is usually for checking to see if the Battery has the capacity to start the engine, if they dim then the battery is down.
If you know you have a good fully charged battery then you have a high resistance connection if they go out.
A high resistance connection could be a bad ground or a dirty connection.
If the battery cables get very hot very fast then you have a bad starter or short to ground.
If you know you have a good fully charged battery then you have a high resistance connection if they go out.
A high resistance connection could be a bad ground or a dirty connection.
If the battery cables get very hot very fast then you have a bad starter or short to ground.
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Joined: Jan 2001
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From: Virginia
Yes, basically when you do the headlight test, you are using the headlights as a voltmeter.
If they stay fairly bright or dim just a little bit when you try to start the truck, then that tells you the voltage in the system is staying high, and the battery is does not have much of a load on it. This is usually a sign of a starter problem or a ignition switch/neutral safety switch problem, since the voltage is staying high, and the battery is waiting there for the current to flow.
If the headlights go completely out, then that is telling you the voltage in the system is going to 0 or close to it. That means the large load of the starter is being applied to the battery, and either the battery is bad or low and can't handle the load, or there is a loose or corroded connection at one of the large battery cable ends that can handle the load of the headlights, but cannot handle the load of the starter, causing too much resistance, which makes the voltage go to 0.
If they stay fairly bright or dim just a little bit when you try to start the truck, then that tells you the voltage in the system is staying high, and the battery is does not have much of a load on it. This is usually a sign of a starter problem or a ignition switch/neutral safety switch problem, since the voltage is staying high, and the battery is waiting there for the current to flow.
If the headlights go completely out, then that is telling you the voltage in the system is going to 0 or close to it. That means the large load of the starter is being applied to the battery, and either the battery is bad or low and can't handle the load, or there is a loose or corroded connection at one of the large battery cable ends that can handle the load of the headlights, but cannot handle the load of the starter, causing too much resistance, which makes the voltage go to 0.
