Cavalier Mk3 electrical problems

Hi,

I've got a couple of problems with my Mk3 Cavalier (a '95 2.5GLS).

Firstly, the rear windscreen/door mirror heaters aren't working. When the button is pressed absolutely nothing happens - no light, no click of a relay, nada. The fuse is OK and there's 12V getting to the fuse terminals. The wiring diag in the Haynes says there's a relay for it, but doesn't mention where it might be found. Is the switch and the relay one and the same? There's 6 pins on the relay in the manual, but only 5 on the switch. If the switch is just a switch, where is the relay?

Secondly, I went onto a dual-carriageway today in 2nd and accellerated fairly hard. As I changed up into 3rd the engine management light came on, shortly followed by the airbag warning light. I pulled over fairly soon after and as the car came to rest the lights went out. I switched off and on, but the lights came back on after I started moving. While I was travelling I dropped the car into neutral, and let it coast. As the revs dropped under about 1000 rpm the lights went out. They came back on when I revved the engine a bit. After the car stood for a few hours I drove back and the lights stayed off.

I shorted the 2 pins on the ecu plug thingy, and the code I read off the flashing dash light was 4-9, which according to this site:

formatting link
means the battery voltage was high.

A few weeks ago I was getting a flickering alternator light on the dash (it went away 'all by itself'), so I'm beginning to think it may be time to get a new one. I've checked the charging voltage with a multimeter and it's about 11.5V which seems a bit on the low side.

Does anyone have any suggestions??? How much is a new alternator likely to be if required?

Thanks in advance,

Iain

Reply to
Iain McLaren
Loading thread data ...

As discussed a few weeks ago, it sounds as though the regulator on your alternator has finally died. The HRW relay coil is connected into the charging lamp circuit so that the HRW can only be brought in when the alternator is charging. It is more than likely that the battery lamp is not coming on at all when the ignition is first switched on. This could be the bulb blown, which is probably caused by the regulator going faulty.

If you check the battery voltage with the engine at 3000rpm, you may find that the voltage will rise above 16V. This is the threshold required to bring up a 'battery voltage high' fault on the engine management system and the airbag. Running it around like this for too long without rectification of the fault could cause the battery to boil dry!

If you install a new alternator, be sure to check that its cooling fan is working OK, and the ducting and heat shield is present and correct. A new alternator will fail in a short time if these items are not as they should be.

HTH

Anthony Remove eight from email to reply.

Reply to
Anthony Britt

Hi,

Thanks again for your advice.

I've not actually checked whether the battery light is coming on when the ignition's first switched on...I've not *noticed* that it's not there, but the absence of a bright red light is hardly noticable .

I did rev the engine while checking the charging voltage, and it didn't rise above 11.5V. I guess it's one of those intermittant things :-( Interesting that about the HRW only working when the battery's charging. Nice idea that!

I presume the regulator can't be changed independantly of the alternator...can it???

Cheers,

Iain

Reply to
Iain McLaren

OK, just been out to the car, switched the ignition on, and no battery light.

The other thing I tried (that I should have put on my first post) was that I tried pulling the high-beam on with the engine running earlier and there was no drop in revs as there should have been with the alternator having to work harder....

Regards,

Iain

Reply to
Iain McLaren

On 26-Sep-04 18:17:38, Iain McLaren said

Iain, for what its worth I think the electrical system in Cavalier's is weird, or haunted, or something. I used to have similar occurrences, which would come and go over the months - didn't have an airbag though. In my case I could live with it, but obviously ymmv, particuarly on a safety related issue.

All the best, Angus Manwaring. (for e-mail remove ANTISPEM)

I need your memories for the Amiga Games Database: A collection of Amiga Game reviews by Amiga players

formatting link

Reply to
Angus Manwaring

Sounds as though the regulator has gone belly-up, although as I said previously the charging tell-tale bulb has probably gone, which has now stopped the alternator charging.

The regulator is replaceable, although by the time you have removed the alternator from the car to get to it, you may as well replace the whole thing with a new part that is certain to work and has a warranty. I am not sure exactly how much a regulator would be. An exchange alternator from Vx is about £125....

HTH

Anthony Remove eight from email to reply.

Reply to
Anthony Britt

Hi again,

Another symptom I forgot to mention was that the windscreen wipers were hellish slow yesterday. I'd half convinced myself that it was because of the very windy conditions, but that would definately indicate a voltage problemo...

Vauxhall say there's 3 ampage rating alternators. A 80A one at about 80 quid (+VAT), a 100A at about 170 and a 130A (not sure what price is).

Anyway, it's going down to our friendly MOT garage this morning for an inspection and price for supply/fitting. I probably won't have chance to do it before the weekend, and the car's needed for a wedding on Sunday so I might have to take the easy option and have it done.

Bit confused about your bulb-charging statement below - will the alternator ONLY charge the battery IF the tell-tale bulb is OK???

Thanks again,

Iain

Reply to
Iain McLaren

On some systems, the bulb forms part of the regulator circuit, and if it blows, the alternator doesn't charge. Decent makers fit a resistor in parallel with the bulb to prevent this.

Reply to
Dave Plowman (News)

80A alternator is fitted to V6 models without Air-con. Air-con models are fitted with a 100A unit, unless it is a CDX or Diplomat with heated seats etc, in which case the 130A part is used..

As Dave mentioned, a resistor is included in the circuit with the ignition lamp to start the alternator charging if the bulb goes, but this can also be damaged (overheated) if the regulator goes TU causing a complete loss of charging.

Anthony Remove eight from email to reply.

Reply to
Anthony Britt

Hi,

Just to let you know the problem's been fixed. I gave the garage the un-enviable task of changing the alternator and bulb. I'm 250 notes worse off, but at least it's done.

Thanks again for your advice!

Iain

Reply to
Iain McLaren

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.