| 40fordor | -- 06-19-2010 @ 5:58 PM |
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My dash indicator has always been in the mid green range until very recently. Now it stays on the border line between yellow and green. When I check voltage at the battery with the rpm's above idle there is about 7.3 volts. The battery is very old and weak will this cause the ampmeter to show the lower current? I would think it should indicate a higher current for a weak battery.
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| shogun1940 | -- 06-19-2010 @ 6:04 PM |
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bad batteries can cause all kinds of weird things. Take the battery to a place that can put load test on it and if there is any doubt, buy a new one.
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| 40guy | -- 06-20-2010 @ 6:30 AM |
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A 1940 battry guage is a voltmeter not an ampmeter. This is provided you don't have an after market guage. Therefore, the guage would indicate the battery voltage not amps.
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| 37RAGTOPMAN | -- 06-20-2010 @ 7:47 AM |
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when the battery gets old it builds up a resistance, like it is charged already and it will not hold a full charge anymore, and will not allow it to charge fully, there for it is only alowing a little amount to charge CHANGE THE BATTERY,if it 3 years or older, it all depends who made and if it was good one or a cheap one,AUTOZONE makes a good 6v battery. I BUY all my batteries from them,have a good warrantee and a good retun policy,and a rewards program, and if and when I have a problem I know were I bought them, solves a lot of thinking were did I buy that battery 4 years ago, buy for my 31 2DR and 37CAB and well as my modern iron,
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| alanwoodieman | -- 06-20-2010 @ 12:54 PM |
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what is the voltage on the battery when the car is not running. local battery store told me it should be around 6.45 or 2.15 volts per cell, but they also said that to know for sure you need a hydrometer to test the specific gravity of each cell. I have been having a problem which was traced to a bad voltage regulator, took gen and bad voltage reg to a rebuilder, got new one from him and let him set it up, voltage running about 7.4 volts at running speed. took it home a put on, ran car ok, two days later battery was dead!!still looking for problem, must be a ground somewhere. with the car off-it shows a voltage drag on a meter between the battery and the frame of 4.5 volts-any answers>
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| supereal | -- 06-20-2010 @ 2:33 PM |
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I suspect you have a "parasitic" drain somewhere. You can put a test light between the battery port and the cable, and with everything shut off, see if the light is lit. If the drain is 4 volts, it shouldn't be that hard to find. The voltages you mention are about right, so follow a circuit diagram like a road map from the battery out into the car. If you don't have a circuit diagram, I can scan one for you. You said you installed a new generator and voltage regulator. Often, the cutout in a regulator sticks, but I think your problem wasn't with the regulator or generator, but elsewhere, and it is still there.
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| alanwoodieman | -- 06-20-2010 @ 6:21 PM |
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Supereal, I have disconnected everything from the circuit-horn relay, brake light swith, voltage regulator,heater switch, cigar lighter, radio, light switch even disconnected the starter relay-still got the drain--got any ideas?
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| shogun1940 | -- 06-20-2010 @ 8:02 PM |
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how about the brake lights going on in the middle of the night,, then find out if its draing through the gen. reg. what else is left This message was edited by shogun1940 on 6-20-10 @ 8:08 PM
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| Johns46coupe | -- 06-20-2010 @ 10:54 PM |
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alanwoddieman, I had a slight drain as measured by the ammeter on my multimeter (didn't register on the car's ammeter because it was so slight). Chased it to an aftermarket turn signal switch. In this case, I would disconnect everything as close to the battery as possible. Then, with an ammeter, connect one thing and measure. If that's ok, add another and measure. When you find the connection that causes a draw, break that one down and disconnect all of it's branches. Then connect one at a time and measure. Eventually you'll find it. John This message was edited by Johns46coupe on 6-20-10 @ 10:56 PM
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| TomO | -- 06-21-2010 @ 7:33 AM |
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40fordor, the battery gauge shows the voltage in the charging circuit when the car is running. An old, sulfated battery will have a high surface charge causing the voltage regulator to react like the battery was fully charged. The battery gauge would then be on the border line between yellow and green or just into the green. Tom
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| TomO | -- 06-21-2010 @ 7:52 AM |
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alanwoodieman, Measuring between the battery NEG post and frame will show your battery voltage. If you measure 6 volts or more across the battery and only get 4 volts when measuring to the frame, you have a poor ground connection. To check for a short causing the battery to go dead, connect the COM lead of the meter to the NEG post and use the POS or + lead of the meter to probe. Start by disconnecting the battery from the driver's side of the starter solenoid and probing the 12 gauge wire. If you read voltage with everything turned off and the clock disconnected, you have a short somewhere. Leave your meter hooked up and start disconnecting the brake lights, horn, ignition switch and lights. The brake lights, dome lights and clock are prime suspects when you have a drain on the battery. Tom
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| supereal | -- 06-21-2010 @ 10:11 AM |
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Looking at the wiring diagram, the unswitched connections to the battery include the horn relay, the input to the starter solenoid, the cigar lighter, the input to the lighting circuit breaker, and to the ignition switch. The other connection is to the BAT terminal on the voltage regular, of course. I'd hook up either a test light or a voltmeter between the battery cable and the battery post and disconnect these places, one by one, until you get no reading on the meter. Measuring current is usually beyond the capacity of a non-professional meter. To do that, place a 1 ohm 10 amp resistor in series with the circuit, and put your voltmeter across the resistor. A reading of .02 volts will indicate a .02 amp (20mA)) key off drain, and so forth. You didn't mention whether you have a circuit diagram. I'm guessing either the horn relay or the circuit breaker is "leaking". If the drain ends with the input to the circuit breaker, then the lighting circuit may have a 'casual" short. I'll scan and send a diagram.
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| supereal | -- 06-21-2010 @ 10:16 AM |
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Here is the circuit diagram for your '40:
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| alanwoodieman | -- 06-22-2010 @ 5:11 PM |
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Superreal, thanks for the diagram,already had several but sometimes it does'nt hurt to have more. I have not been able to work on it again yet. I have the circuit breaker out, the horn reg, voltage reg,brake light switch, starter solenoid, disconnected the feed to the light switch, ign switch, cigar lighter,radio, I will have to remove the radio to get at the wiring for the dome light.I will do that tomorrow. I am begining to think my wagon is MAD at me for working on other flatheads, rewired a 36, fixed wiring in a 35, and am working on the wiring in a 34 got any other ideas short of stripping out the harness and starting over?
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| supereal | -- 06-23-2010 @ 9:42 AM |
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Tracking down a "casual" short isn't fun, and takes a lot of time. I'd keep isolating each circuit before you replace the wire loom. That is a big job that is often not necessary. We have run into this type of wiring problem when sections have been altered or bypassed, and occasionally a "universal" harness is used and unneeded connections are not removed or insulated. I, too, know the suspicion of "inane animosity of inanimate objects".
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| alanwoodieman | -- 06-29-2010 @ 8:33 AM |
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Superreal, I have been working on the short in my wiring harness and have really found nothing!! The only thing I remotely found was the horn wire connection in the wiring cover on firewall had slipped down the connector but could not really say that was it. Does not light up a test light now and I did find one other problem but it could not have caused the short problem. Thanks to you and all who made suggestions to try and help me. I did accuse my buddy with the 35 of putting a hex on my wagon!!
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| supereal | -- 06-29-2010 @ 10:52 AM |
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Most "casual" shorts are the hardest to isolate. As it appears to happen when the ignition switch is off, I'd suspect the two things I mentioned earlier: the horn relay and the lighting breaker. Often, there isn't enough current to sound the horn, but enough to cause the relay to pull, sometimes by a short to ground in the steering wheel to switch leg of the circuit. I always recommend a master cutoff switch for old cars, as the cotton covered rubber insulated wires usually are crumbling and any high resistance connection or short can cause not only a dead battery, but a fire, as well. Sometimes it does seem as though a hex is at work, but you will find the problem. That's why we can it a "hobby"!
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