71 Delta Gen Light and Blower Fan Q's
April 26th, 2013, 01:50 PM
#1
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71 Delta Gen Light and Blower Fan Q's
I'm finishing up the last few gremlins on the 71 Delta 88 I've been building here and have 2 quick electrical questions that are unrelated to each other.
The Gen light in the dash seems to always be on....however I probed the battery with the car running at idle and I'm getting about 15.1V. The battery is probably a little low from working on the car with the doors open so not sure if that's why the voltage is so high or if the car is overcharging and that's why the light is on? Will this light come on for an overcharging condition? Anything else I should check? Could I have a bad connection somewhere else making the light stay on?
And the blower motor seems to always be running right now whenever there is ignition power and it won't change speeds if I move the switch between different positions. Does this sound like a switch issue or maybe some sort of grounding issue in the circuit?
Thanks in advance for any help.
The Gen light in the dash seems to always be on....however I probed the battery with the car running at idle and I'm getting about 15.1V. The battery is probably a little low from working on the car with the doors open so not sure if that's why the voltage is so high or if the car is overcharging and that's why the light is on? Will this light come on for an overcharging condition? Anything else I should check? Could I have a bad connection somewhere else making the light stay on?
And the blower motor seems to always be running right now whenever there is ignition power and it won't change speeds if I move the switch between different positions. Does this sound like a switch issue or maybe some sort of grounding issue in the circuit?
Thanks in advance for any help.
April 26th, 2013, 02:38 PM
#2
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Addressing the blower motor first, that's normal for these cars. '71 was the year GM introduced "flow-through" ventilation, and one of the features was a blower fan that always ran at low speed. You'll notice you have grilles in the trunk lid. Those were part of that system. In later years, the trunk lid vents went away, and little vents appeared in the door jambs.
About your charging system, ~15 V at the battery when the engine is running is normal. Your battery is not being overcharged.
When you say the gen light is always on, what do you mean by "always" as there are two possibilities to consider.
1) is the gen light on with the ignition off? If so, disconnect the #1 and #2 connectors at the alternator. If the lamp goes off, replace the rectifier bridge in the alternator. If the light stays on, there is a short circuit between wires #1 and #2 in the harness.
2) is the gen light on with the engine running? First check the alternator drive belt to make sure it's not slipping, and check the wiring at the alternator and battery as well as the connecting cables. If the problem persists, stop the engine, and connect a voltmeter between the BAT terminal on the alternator and ground. With the ignition on, if you get zero voltage, there is an open circuit between the BAT terminal and the junction block or between the junction block and the starter.
If, on the other hand, you get battery voltage with the key on, disconnect wires 1 and 2 at the alternator and connect a voltmeter between #1 connector and ground. If you get zero voltage, there is an open circuit in wire #1 between the connector and the ignition switch. If you get battery voltage, things get more complicated as far as testing, but the end result is replacing either the regulator or the alternator.
By the way, the service manual does state that excessive use of the battery, such as leaving the headlights on with engine off or running the rear defogger excessively can drain the battery enough to cause the gen light to be on for a while until the battery recovers. You say you've been leaving the doors open a lot while working on the car without disconnecting the battery, which would leave the courtesy light on continuously. Is the gen light problem recent, perhaps coinciding with the excessive door-being-left-open, or has it been this way longer?
About your charging system, ~15 V at the battery when the engine is running is normal. Your battery is not being overcharged.
When you say the gen light is always on, what do you mean by "always" as there are two possibilities to consider.
1) is the gen light on with the ignition off? If so, disconnect the #1 and #2 connectors at the alternator. If the lamp goes off, replace the rectifier bridge in the alternator. If the light stays on, there is a short circuit between wires #1 and #2 in the harness.
2) is the gen light on with the engine running? First check the alternator drive belt to make sure it's not slipping, and check the wiring at the alternator and battery as well as the connecting cables. If the problem persists, stop the engine, and connect a voltmeter between the BAT terminal on the alternator and ground. With the ignition on, if you get zero voltage, there is an open circuit between the BAT terminal and the junction block or between the junction block and the starter.
If, on the other hand, you get battery voltage with the key on, disconnect wires 1 and 2 at the alternator and connect a voltmeter between #1 connector and ground. If you get zero voltage, there is an open circuit in wire #1 between the connector and the ignition switch. If you get battery voltage, things get more complicated as far as testing, but the end result is replacing either the regulator or the alternator.
By the way, the service manual does state that excessive use of the battery, such as leaving the headlights on with engine off or running the rear defogger excessively can drain the battery enough to cause the gen light to be on for a while until the battery recovers. You say you've been leaving the doors open a lot while working on the car without disconnecting the battery, which would leave the courtesy light on continuously. Is the gen light problem recent, perhaps coinciding with the excessive door-being-left-open, or has it been this way longer?
Last edited by jaunty75; April 26th, 2013 at 05:12 PM.
April 26th, 2013, 03:23 PM
#4
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Failure of the blower motor resistor is usually indicated if the blower will run only at the highest speeds. If the blower speed can't be changed at all, I would suspect a bad switch?
April 26th, 2013, 05:06 PM
#5
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Jaunty thanks for the great explanation for the GEN light....I'll dig into it on monday. The fan switch I'll have to try pulling out if I can and put a meter to it and see if it's the actual switch or something else in the circuit.
April 29th, 2013, 08:26 AM
#6
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Hey Jaunty I started digging into this GEN light issue this morning and I'm stuck again. The light only comes on when the engine is running.
I cleaned all of the connections on the alternator as well as the regulator. I also installed a new regulator for good measure because the old one looked pretty crappy and since this is a show car a nice new one for $20 looks better anyway. Still no change.
Also I took the alternator back out and had the local parts store throw it on the test bench and it looks good.
I have voltage between the BAT and ground with ignition on. However for the test of wires 1 & 2 I'm not sure which wire is which. On one of the wires I show about 6V and just about 0V on the other.
This issue occurs even after the battery has been on a charger for several hours and the fuse for the interior lights was pulled so they didn't drain the battery. Would a bad battery cause the light to go out? The battery was new about 2 years ago but the car hasn't been driven yet with it and it sat discharged for several months I believe.
I cleaned all of the connections on the alternator as well as the regulator. I also installed a new regulator for good measure because the old one looked pretty crappy and since this is a show car a nice new one for $20 looks better anyway. Still no change.
Also I took the alternator back out and had the local parts store throw it on the test bench and it looks good.
I have voltage between the BAT and ground with ignition on. However for the test of wires 1 & 2 I'm not sure which wire is which. On one of the wires I show about 6V and just about 0V on the other.
This issue occurs even after the battery has been on a charger for several hours and the fuse for the interior lights was pulled so they didn't drain the battery. Would a bad battery cause the light to go out? The battery was new about 2 years ago but the car hasn't been driven yet with it and it sat discharged for several months I believe.
April 29th, 2013, 08:42 AM
#7
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Location: southeastern Michigan
Posts: 14,150
With the regulator and alternator ruled out, that leaves possibly the battery. Even though it's been on a charger, if it has a bad cell, no amount of charging will fix it. Can you put in a battery from another car just to check instead of having to buy a new one? Maybe you could take the battery in for a check like you did the alternator.
Taking out the courtesy lights fuse rules out a short in that circuit, but other circuits could be suspect (taillights, stoplights, windshield wipers, radio, etc.). With the battery having sat for two years, I would suspect that first. If it checks out, then maybe you want to remove all the fuses and see if the gen light is on. If it's not, then you can replace the fuses one by one until it does go on, and then you know the circuit with the current draw.
Another quick question: when the GEN light is on, is it dim, or is it full brightness? My '73 chassis service manual says that, if, with the engine running, the GEN light is dim, the solution is to replace the 10 amp "GAUGES, TRANS." fuse in the fuse block.
Another quick question: the GEN light should be on at full brightness with the ignition on and the engine stopped. If it's on but dim, the solution is the same as above.
Taking out the courtesy lights fuse rules out a short in that circuit, but other circuits could be suspect (taillights, stoplights, windshield wipers, radio, etc.). With the battery having sat for two years, I would suspect that first. If it checks out, then maybe you want to remove all the fuses and see if the gen light is on. If it's not, then you can replace the fuses one by one until it does go on, and then you know the circuit with the current draw.
Another quick question: when the GEN light is on, is it dim, or is it full brightness? My '73 chassis service manual says that, if, with the engine running, the GEN light is dim, the solution is to replace the 10 amp "GAUGES, TRANS." fuse in the fuse block.
Another quick question: the GEN light should be on at full brightness with the ignition on and the engine stopped. If it's on but dim, the solution is the same as above.
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