what is this and why does it do this ???

[menostig]

Ok, I do recognise it as a red battery, but is it a "red-top" of the type available from RaceTech?

I ask because it wouldn't serve head-lights & rad-fans without drooping below 12v on the (accurate) gauge.

Readings:
11.5V - ignition on, fuel-pump on, a/c off, everything-else off
13V - normal driving
12.7V - normal driving, fans-on
12V ish - head-lights on, fans-on
<12V - stick something else on e.g. a/c or extra cooling fan in the rear side air intake

Chief suspect is the battery which is over 7yrs old.

cheers
Roger

[menostig]

Or I should have said, would a RaceTech 40 fit ? The dimensions are 10d*20h*25w (cm).

[G Man]

Surely your alternator needs checking me thinks ...

[YIIHAA]

I'd say chief suspect is the ignition switch wiring in an Ultima of that vintage. Have you tried measuring the voltage at the terminals of the battery? My volts gauge use to drop to 11.5 when the fan/lights were on, but the voltage at the terminals of the battery was a healthy 13.5. The voltage drop was across the ignition switch.

[menostig]

Shouldn'the battery read more than 11.5v across the terminals with a multi-meter when everything is off ?

I could measure across the battery terminals when fans are on and lights are on I suppose that would eliminate the battery. And then measure across the ignition switch terminals (but the switch is recent) ?

How do I test the alternator though ?

thanks
Roger
(cursing that it's not an easy answer)

[builder]

menostig said:

Shouldn'the battery read more than 11.5v across the terminals with a multi-meter when everything is off ?

I could measure across the battery terminals when fans are on and lights are on I suppose that would eliminate the battery. And then measure across the ignition switch terminals (but the switch is recent) ?

How do I test the alternator though ?

thanks
Roger
(cursing that it's not an easy answer)

Save the good cursing for something serious!

Your local auto part store should be able to test your alternator (ALT) for free. You could test it yourself with an induction meter. If it's not the switch, as suggested above, it is probably your ALT.

Someone will jump in here, but I think the right way to test the switch would be to measure across the switch terminals with the key in the "ON" position (with everything else, including the engine, off). Compare that to the voltage at the battery terminals (again, with everything off). The battery should be 13V++, when fully charged. The only other switch-related problem I can think of would be the thickness of the wires. But, the switch doesn't contain "starter" voltage, does it? I mean, certainly there's a solenoid, isn't there? (Haven't gotten that far yet).

Lastly, it could be the battery (BAT). When you take the ALT for testing, take the BAT too.

The way I understand it, with my limited electrical knowledge, you car actually runs more off juice from the ALT...not really the BAT. The BAT is there sort of as a buffer and to support "key-off" electrical requirements/demands, as well as starting. The ALT will charge the BAT last. When there are other electrical demands (i.e., lights, fans, 30A-vibrator), they come first.

I may be off, but I like to think of the BAT as an Accusump for electricity. If the pressure (from the ALT) isn't enough to fill the tank (the BAT), there's no reserve to pump in when you need it. That's my story and I am sticking to it...

Edited by builder on Monday 26th June 05:04

[craig-ultima]

You probably have a bad cell in the battery. What a battery should read on open circuit depends on the battery technology used. A good way to test to see if you have a bad cell is to charge the battery up, then put a medium load on it (such as the fuel pump, or headlights). If you get a big drop in voltage, then one of the cells is starting to increase in resistance, and hence going bad.

Seven years old? I'd put in a new battery.

[menostig]

Ok, some reading and some measurements and some driving gives me these observations:
- alternator is primary source when engine is running
- battery reads 12v across the terminals
- guage in car is in agreement with across the battery terminal measurments under all load conditions
- ignition switch drops max 0.5V across its terminals under heaviest load (fans, headlights)
- Alternator gives 13.5v when engine running
- this drops to 13v when fans and head-lights are on
- and the alternator warning light glows in time with indicators (!) or wipers when add either of their loads to this

Question
- how much slack on alternator belt ?
- should there be a very slight whining sound from the alternator at fast idle (1200rpm) ?

Conclusions
- think ignition switch is ok
- battery is a bit low, will top-up charge and measure again, then load test and replace if necessary
- alternator is a bit weak, should really be 14V, is the main suspect now unless battery fails load test

[andygtt]

worth noting that whilst these 'red top' batteries are very good, You must not allow them to lose their charge. As long as it has always had some sort of charge your fine, but when they run fully flat they will never be the same again and need replacing.

[burlguy]

Just replace both, if the alternator has gone bad, (ie whining at 1200 rpm) it has put a load to great on a 7 year old battery. You replace the alternator then the battery goes out completely ruining a new alternator. I have worked 4 different shops and have seen it all to often. Replace both and dont worry. Belt deflection pushing firmly with 2 or 3 fingers on it from above between pulleys should be no greater than half an inch. I watched a ford power steering unit with double belts get broke two days ago by the owner applying to much tension. As long as the belt is clean half inch should do.

[splatspeed]

ok easiest way to check battery is remove and jump the leads to a known good battery

alternator should kick out 13.5 no problem should sit min at 12.7

sound like one phase is gone of the alternator if the light is very dim

used to happen on my cortinas a lot

alternators ned a voltage to excite them but once they have that they should be 13 v no problems under up to 55 amp load

do you know the rating for your alternator

sean

[davefiddes]

If the alternator is pushing out 13.5V then it's fine. Then again I have seen alternators that seemed to work fine but one or more phases had gone. Problem showed up when on a trip to a local dyno they couldn't get a reliable RPM signal...odd bet it's their dodgy signal processing...one hot day a few months later the idiot light come on. Ooops.

My bet would be the battery though. It should hold the charge. From the numbers it looks like one of the cells has gone.

[menostig]

Ha. Drove to Nacton Auto Electrics near ipswich who were more than happy to test battery and alternator. Both passed tests with flying colours. Guess what - my volts guage underreads by 1.2V. Any my £5 multi-meter that has been dropped and trodden on does too.

[steve_d]

So this whole post was nothing more than attention seeking.
I think you need to get professional help.

Steve

[menostig]

Attention seeking ? Surely can't accuse an ultima driver of that ?