| Author |
Message |
    
Keith Armstrong
| | Posted on Wednesday, February 27, 2002 - 01:32 pm: | 
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Ok, my yellow top optima tested bad (wouldn't stay charged on the bench with a load applied), so I replaced it.
Now if I leave the '94 Disco alone overnight with the alarm set, it won't start in the morning. I charge it with the 8 to 0 ohm floating rate charger and it's ok.
I check the battery voltage today: Ignition and everything off it's 12.54, then with engine running and only the heater fan on the battery voiltage is 13.54.
I was looking for soimething over 14 volts, no?
So what, I've got a bad alternator / voltage regulator_and_a problem with the alarm wiring?
Thanks... |
Paul T. Schram
| | Posted on Wednesday, February 27, 2002 - 04:48 pm: |
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Keith:
You have just found one of the major weak links on the Disco.
Let us go after this logically so that we don't spend money needlessly and also don't miss the real problem.
Let's start with the things you can do at home and that don't cost anything or require disassembly.
First off, I'm assuming you have some electrical test equipment as you'd commented that you had measured the voltages. Tonight, when you're ready to leave the truck disconnect the battery and place your ammeter in series with the battery. This will give you some indication as to the load that is being applied to the battery when nobody's supposed to be home (did they leave the lights on?). You will want to start with the highest amp range your meter has just in case there is something major wrong-let's not wipe out your meter too! At this point, you will have an indication as to the absolute current draw in a quiescent condition. The problem I have now is that I don't know what the current draw of the alarm and ECU should be. We could calculate a maximum from the fuse ratings and applying Ohm's law. If the current draw is negligible say, maybe in the 500 milliamp range (although that would drain a battery pretty quickly) we could say that the current drain is not out of the ordinary. 100 ma might be more like it-again, I do not know the at-rest current consumption of a Rover's ECU and alarm. If we find that the current draw is much higher than half an amp, we can then start pulling fuses until the current draw drops precipitously, then, trace that particular circuit to its starting point looking for things out of the ordinary. At this point, you might be finished and can progress to go and collect $200.
If the sleeping current draw is acceptable, then you should probably have the alternator checked. Your charging voltage is somewhat low, but I don't want to jump to conclusions and mask the root cause of the problem.
Be prepared. My Disco is on its fourth alternator. I'm somewhat surprised you haven't encountered any other problems. I've found the Rovers to be very particular about their operating voltages. I attribute my rough running at start-up to be due to low battery voltage.
Let us know what you find.
Paul
'95 Disco |
bryan
| | Posted on Wednesday, February 27, 2002 - 06:30 pm: |
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Keith,
I had a similar problem, battery running down for no reason. Took it to the dealer, 2 weeks and a wad of cash later they told me all they did was check and clean all the grounds. I wish I had found the following info before taking it in for repair. I think I found this at the Atlantic British web site.
Poor grounds can cause numerous problems on 1994 - 1996 Discoverys. The following are main ground locations and the components they effect. To clean the contact surface, remove the fastener and use a wire brush to clean the post, connector and nut as needed. Spraying on a little contact cleaner may help, too. If the contact point is painted, a star washer can also be added to improve the connection.
Check these ground locations:
1. Right inner fender, behind the battery. Battery and EMC on 1994 & 1995 models.
2. Below the battery, inside the right frame rail. Battery ground.
3. Right of the left cylinder head. ECU, AC compressor clutch on 1994 & 1995 models.
4. Right frame rail, inside wheel well. Starter.
5. Left footwell, behind trim panel. ECM, key switch, radio, OBDII data link.
6. Right footwell, behind trim panel. Starter solenoid relay, park-neutral position switch, alarm, data link connector.
7. Left side of luggage compartment, behind access panel for taillights, above light assembly. Fuel pump, fuel level sensor. |
Keith
| | Posted on Wednesday, February 27, 2002 - 08:38 pm: |
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Thanks Guys,
Oh no Paul, this is the seventh alternator...just turns out that five of the replacement/rebuilt units that I bought from the local import auto parts guy were bad
I kept my o.e. alternator and have had it rebuilt, so its in the rear as a spare. The current rebuilt unit in the truck is lifetime warranty, but I want to be sure its bad before I swap it out.
Now with an expected sleeping draw (I do like that one) of something less than 500mA, I'm not going to let the smoke out of my little Radio Shack VOM am I?
I'll give it a shot Thursday morning when its light out.
Thanks again... |
Paul T. Schram (Paulschram)
| | Posted on Thursday, February 28, 2002 - 12:07 pm: |
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Keith:
Bad Alternators: Fortunately, I have only had to deal with the one. The PO of my truck is a lawyer and is still fighting with a Rover vendor I'll not name to preserve what decorum there is here. Given his tenacity when it's him being screwed (lawyers do it so well but complain when it happens to them), I suspect he will win.
For what it's worth, Atlantic British supposedly tests all of their alternators and writes the voltage and current on the outside of the box! I know that the box mine came out of had a voltage and current written on the box.
Your radio shack VOM should have a range of at least one amp. Start there, then go down.
And, if it does let the smoke out, buy a Fluke next time. Not cracking on your Radio Shack meter, I used one for a long time before I bought my Fluke in the parking lot of the local electronic surplus shop. My father, who has been doing these things for the past 70 years, still uses his $5.00 Radio Shack meter he has had for 20 years. I believe his first meter either said Marconi or Volta on it:-). Of course, he's so old, they only had four elements Fire, water, etc.
Peace,
Paul |
Keith
| | Posted on Thursday, February 28, 2002 - 05:31 pm: |
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Hah!
Man I needed that today. I have some of those same equipment items around. My Dad was an E.E. and we had all kinds of components in the garage when I was a kid.
I've been not using the alarm for the past couple of days and not had any trouble with starting. That kinda narrows my task down a little.
As soon as tax time is past, I'll get to tracing circuits.
Thanks guys...KAA |
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