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MG MGB GT V8 Factory Originals Technical - Charging System Problems
My 77 Rubber Bumper with 215 V8 is causing me to be very frustrated eith electrical issues. They are as follows.
1) Battery drains if the car sits for a couple of hours.
Has an Optima battery and a Mitsubishi Alternator. 55 amps.
2) I have installed a battery isolator and even then the battery drains. Battery has tested good as well as alternator.
3) I have tried to identify the source of the drain but I'm still at a loss. The only drain that i have identified is from Radio Memory.
It is not funny when someone comments me on my car and then it will not start. Nothing has been added to the electrical system recently.
4) Sometimes turn signals light but do not operate as they should, yet all bulbs are in working order.
5) Horn currently does not work, although i understand that this could be the switch that has failed. Replaced fuse to no avail.
Suggestions, advice anyone? Thanks very much. Wiring loom is 5 years old.
|Check all positive battery terminal connections. At the battery, the solenoid, and the fuse box. A loose battery connection can cause some of those symptoms. What optima battery do you have? Red, Yellow, or Blue? When you connect a test light to the body of the car, and the negative terminal, does it light up? It shouldn't but if it does, there might be a power leak somewhere.|
|Where is your isolator? If it is in the main battery cable at the battery, and there are no other cables coming off the battery to bypass it, then either the battery *is* faulty or something like the clamp plate is partially shorting it out. I suspect the latter since flattening within a couple of hours is a big drain. Lighting but non flashing turn signals is a symptom of low voltage or bad connections, and given the other problem I would suspect the former. Measure the voltage between the brown at the fusebox and ground with the ignition off, and with the engine running at a fast idle with minimal electrical load. The former should be about 12.8v with a good battery and no heavy drains, the latter about 14.5v with a good alt and no heavy drains.|
I will try these steps and let you guys know what I find. It embarassed me again this evening. It is becoming very frustrating. Thanks guys.
| First ,get your battery checked. it sounds like it can't hold a charge. I've had similar experiences & it's always been a dud battery. It usually happens within a day or two of the battery warrenty expiring !|
Another possible route if your battery is OK is to connect an "ampmeter" in the primary live feed from the battery. You can then measure the drain. By dissconnecting the fuses and other items connected to the battery one by one you can eliminate the areas not causing the drain. That way at least you will know where you should (or shouldn't) be looking).
|How was your battery checked?|
I have had batteries checked using that big two handled thing which they put accross the terminals only to find later that the battery is a dud. I think that the only sure way to test a battery is to test each cell separately using a hydrometer. This always seems to be accurate. Maybe Paul can comment on this.
Today I took off the alternator and the battery and had them both checked. The verdict is the alternator is fine, but the Red Optima battery was declared a dud. I have since reinstalled both components and will monitor the operation of the system closely to see if the faults persist. In the meantime, thanks to all you guys for your kind suggestions and advice. Tony, how is your V8 coming along? Is it ready for a visit yet?
|Had much the same problem. Found out I had both a bad alternator and a bad (yes) brand new Optima battery. Optima's are good but just like everthing else they can have problems.|
|Marc - I've seen the gadget you mention, it is a very low resistance i.e. a large load, probably not as much as cranking, with a voltmeter you put across the battery terminals for a given length of time and see how the voltage holds up i.e. its capacity. In my BT days where each *cell* of a 50v battery stood 3ft high by 2ft by 1ft we used to use a hydrometer, but that was to see if it was fully charged, not check the capacity.|
Never use the hot battery lead for testing, if something touches bodywork you will get a large arc which could ignite battery gases. When doing any work on the battery always disconnect the battery ground lead first and reconnect it last, and it makes no difference to the test when checking for a drain if you use the ground lead instead of the hot lead. Be careful connecting an ammeter in series with the battery, if you have a large drain, larger than the capacity of the instrument, you may damage it or the leads, and get an arc when connecting and disconnecting it. Much safer to use an analogue *voltmeter* on its 12v scale in place of the battery ground lead which will not spark when connected and disconnected. If there is any drain at all it will register some voltage. On my cars the normal reverse leaksge of the alternator diodes causes a few volts to be displayed and this can be ignored. But if you see 12v displayed you have a significant drain and should investigate it, the first step of which is to make sure the doors are shut, then unplug the alt and see if it goes away. Without the alt connected, or on dynamo equipped cars, there should never be a drain, unless it is a clock, radio memory, or an alarm.
It is very slow progress, but progress never the less. The engine compartment mods and the steering mods are completed so the engine now fits with the steering installed. I am still repairing "camoflaged" accident damge from a previous owner.
Come on round whenever you like, I'm at home Monday and Tuesday, Reno the the rest of the week for "Hot August Nights". I'm also at home next weekend.
This thread was discussed between 28/07/2003 and 03/08/2003
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