G'day.. heres the story.

1 month ago dash voltage guage starts showing no charging (like sitting -5) then next time I start it, its charging.

Thinking my alternator is getting buggered, I get it service (new brushes, regulator etc).

Put it back on and its fine for two drives, then it goes back to showing no charging, then next start its charging etc etc.

Here's the strange thing: When it shows no charging, the oil presure guage read higher than normal and the temp guage reads lower than normal !!??

Now I haven't managed to get a voltmeter onto it when its not charging( according to the guage)..should be ok since all the insides of the alternator were replaced.

What the heck is going on?? is there some fault causing this...real weird that the other guages read funny as same time.

Help if ya can:lala:

 

Voltmeter would be the best piece of equipment to verify the alternator is charging/outputting voltage properly. The dash gauge (all of the vitals gauges really) is mainly for decoration.
Since there is more than one problem at the same time with your gauges though, I would suspect that the harness plugs that the cluster connects into are becoming dirty/corroded and the contacts are becomming faulty (causes faulty ground in the few cases I've encountered). Pull the cluster and clean all the contact points and use a dielectric grease then reinstall.

 

Thanx for reply...when you say cluster..you mean dash cluster?
If so..I'm sorta half way through getting that cluster out....Do I have to disconnect the speedo cable?? If so its bloddy hard to get at. !!??

 

Also check the guage itself, it just pull out with 2 fasteners and clean the resistor that is held in the back of the guage with the 2 hex nuts with contact cleaner and remount it-do not overtighten it as it will crack. If the contact point where the hex nut attaches to the resistor is black you guage may be giving a false reading.

 

Yeah, you have to take off the speedo cable to remove the cluster. If you reach up behind the dash and feel behind the speedo, you will feel a small metal tab right around the cable. Push it towards the cluster and the cable slides right off.

There are also a couple grounds behind the dash, to either side of the cluster. If those contacts are going bad, that could also give you faulty readings.

Matt

 

Just got a multi meter onto the car when its was showing under charge... reading says 11.65 volts coming out of alternator.
If the alternator has just been rebuilt...what else could it be?

Obviously not a guage problem now

 

It is not unusual to get a bad remanufactured alt. To test, do this. Remove the heavy wire from the rear and measure it with the key off, it should read 12 volts or whatever the battery is reading. That tells you that the fuse link between that wire and the battery is good. Next, pull the plug from the top of the alt. With the key on engine off measure each wire on that plug. One should read battery voltage, the other one will be a half a volt or so lower. If they are OK suspect the alt. As always make sure grounds are tight, remember the alt gets it's ground through the case. Also, check the battery with the key off and all accessories off. You should read approx 12.2-12.6 volts. Anything lower charge the battery FIRST before troubleshooting the charging system. LOL, Dan

 

Hey...Danno...Just had a thought...If the rectifier was bad intermitantly would this cause the fault I'm seeing?

 

Yes, or a bad connection to or from the rectifier pack. You might want to get someone to watch the meter and try tapping the alt with a rubber mallet, or try moving wires around. What is the battery voltage with the car off?