Electrical Problem- Gen 3 Alternator replacement

[Benckj]

Haven’t run the car in a month or so meaning battery was flat. Threw the smart charger onto it overnight and car starts fine next day except I had a red engine light up as well as battery symbol.

Checked battery and it was not being charged from alternator. Fuses are ok but cannot pull relay in frunk to check. Need to find a needle nose pliers to assist.

Possibilities??

98 SW20 with numerous mods. Rebuilt alternator 10k ago with no other electrical issues.

[Benckj]

Pulled out BGB and according to CH 18 I need to check the Main Relay IGN. Found no continuity between pins 1&3 so think this may be the issue. Time to rumish through my parts bin to see if I have a spare.

[Benckj]

Got another working MR2 so decided to swap the relays and see problem followed part. Tested working one and has same lack of continuity between 1&3 but swapped anyway. No change to engine and batttey lights in turbo with new IGN relay. Time for more investigation.

Ideas?

[ClanFever]

My new alternator died within a couple hundred kms cause I got a stone in it. Can we swap alternator? Could start with battery, battery might not be accepting charge from alternator due to being dead, or something weird like that.

[tw2]

Not a bad idea to have the battery tested to rule it out.

[Benckj]

Battery is only a year old and accepts a charge ok from mains power charger. Alternator is not putting out anything so seem to think it’s a circuit issue. Was fine last time I drove and problem only occurred after sitting idle for month or so. All electrical equipment works with engine running fine. Battery now at 11.5v so might throw charger back on and see if any change.

[Benckj]

Chucked on charger and started car about1/2 he later leaving charger connected. Battery sitting at 14v but dash lights still on. More investigation required.

[GDII]

I have had many issues with alternators in my MR2. At least 5 failures of different types over 10 years.

The red engine light with a fan is the intercooler fan system either failed or not enough voltage, battery is the battery charge being too low and the NAs get a CAT light due to low voltage. Not sure if the turbo has that light.

Belt not broken or slipping?
Mounting loose or broken?
Slip ring worn or gummed up?
Diode gone?
Voltage regulator stopped working?

It's not often in an MR2 that they don't charge for other reasons. Your grounds are probably good, your battery is probably OK even after going flat but still should check that.

[mknz]

Which battery light? Orange is battery water level. The red one is the one you don't want to see.

11.5V is dangerously low for a battery. Check the voltage of it after leaving it for a couple of days (not on the charger)

[Benckj]

It’s the red engine and battery light. I should mention I am running an after market EMS. Not sure where warning lights are generated from but I will connect laptop tomorrow and see if it offers some clue.

Hope it’s not the alternator as it can be a bitch to pull. If so I’ll install a new 120amp model from the States. Although I have A2W IC I still run an IC fan to circulate air from RH side vent.

Fan belt tight and not slipping. Battery and terminals all good. Still need to give battery a good charge but it seems to be holding over 12v at this stage.

Keep ideas coming.

[mknz]

12.0V is low, you normally need 12.6V to start the car and after a couple of days of sitting it should be at 12.7-12.8V at least

[GDII]

The battery light comes from the charge circuit and doesn't matter what EMS is installed.
The red engine light with a fan on the left (looks like the infinity symbol) is from the intercooler fan ECU and again doesn't matter what EMS is installed.
The CAT temp is a muffler looking thing with heat waves on top. These all light up when the electrical system voltage is too low.
The 3 lights that are not seatbelt and parking brake.
https://www.imoc.co.uk/forums/viewtopic.php?p=1438436

Like Michael said you need to check the battery voltage after leaving it a few days to rule that one out. Then look at the alternator as the 3 parts can stop working at any time. Brushes/slip ring, diodes and voltage regulator.

[Benckj]

Issue started after I charged battery overnight. It was over 13.5v at that time. Battery is an Excide Extreme rated at 730cca and 90ahr. I could swap in another if it’s suspect but given I left the battery charger connected when test running engine the lights were both present.

[GDII]

Does a battery charger create the same output as an alternator? I thought they charged a lot slower?

[Benckj]

Well it looks like I have more investigation work to do tomorrow. Symptoms do point to alternator but I suspect possible wiring issue. Since car hasn’t been used recently maybe a vermin decided to nibble on my harness. Best poke a torch around underbelly and see if something looks out of place.

Might pull the trigger and order another alternator from the States. It’s been on my mod list for some time as prefer to have a little more electrical grunt given all the goodies installed.

My charger pokes out 20amps but I monitored the battery voltage with engine running and it was over 13.5v. If engine required more current than volts would drop.