Output of stock alternator

heyjpark1 · Jan 4, 2009

Who knows the output of the alternator on the Renix-era rigs? It seems to me that when I turn on the heater, lights or other accessories the voltmeter drops excessively (disclaimer: it is the stock gauge cluster voltmeter.

I'm ordering a complete battery cable & grounds set from 5-90 because I suspect it could be a ground issue, and I know I need to hook up an aftermarket voltmeter (and possibly an ammeter). In the meantime, I'm curious if the alternator output is sufficient to run all the accessories in addition to meeting the demands of the engine.

5-90 · Jan 4, 2009

80A or less, OEM. Varies slightly by specific year and engine.

(You should have asked - I have a catalogue of OEMR alternators with ratings...:idea

heyjpark1 · Jan 6, 2009

So the question still stands: is the stock output of the alternator (assuming Renix era 4.0) enough to power all the accessories and the engine management goodies or does the battery need to kick in?

TiRod · Jan 7, 2009

I have a '90 - and yeah, the voltmeter drops right down to the red line when operating everything on a cold night. Seems to do it more now than years ago.

I suspect the alt cable need replacing - it's notoriously small. A volt drop check would be nice, but replacing a stock cable after 18 years has some sense to it, too. I've done all the rest.

I've driven old cars - my last two were a '80 F150 and a '66 Mustang. Old wiring harnesses lose voltage and get worse, never better. You can't go wrong putting in a nice fresh cable, or even wiring harness, to deliver full power. It's the real cure to power door locks, but the relays are a great quick fix.

.40CalPatriot · Jan 7, 2009

You should be fine once you get 5-90's kit. The main problem with the voltage drop is the small guage wires and bad grounds. I need to get myself a kit from 5-90 here soon. I dont know how I am surviving with 2 subs fog lights ac/heat blasting and regular driving lights, I almost hit the red!

5-90 · Jan 7, 2009

TiRod said:
I have a '90 - and yeah, the voltmeter drops right down to the red line when operating everything on a cold night. Seems to do it more now than years ago.

I suspect the alt cable need replacing - it's notoriously small. A volt drop check would be nice, but replacing a stock cable after 18 years has some sense to it, too. I've done all the rest.

I've driven old cars - my last two were a '80 F150 and a '66 Mustang. Old wiring harnesses lose voltage and get worse, never better. You can't go wrong putting in a nice fresh cable, or even wiring harness, to deliver full power. It's the real cure to power door locks, but the relays are a great quick fix.

All too true. The lugs could usually stand a good cleaning as well (it's a temporary fix, eliminating contaminated connections,) but replacing with a larger-gage wire will reduce conductor losses, which helps.

Theoretically, the alternator is "just larger" than the anticipated maximum draw, but that's a bit shady as well - maximum alternator output can vary by -5/+10% from rated. That's why "just larger" is usually "enough" (not really, but how often do you run everything?)

OEM mains run about 8AWG.

Output of stock alternator

heyjpark1

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5-90

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heyjpark1

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TiRod

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.40CalPatriot

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5-90

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