Renix no-charge (new battery, new problem)

The old '88 sat for a while. Needed a new battery, so I got an Autozone Gold one.

Now it stopped charging. Used to sit on the 14 when running, down to 12ish when not running. Now it doesn't change when running; started at around 12 and is down lower.

Autozone says the alt is putting out 12 and is bad.

I'm thinking I'll just get a new 100 amp alternator and hopefully be done with it.

Could anything else be causing this problem?

Nope, you need an alternator.

Thanks, do you know if the voltage regulator could be a problem here too? Is it built into the alternator? ('88 Renix)

Regulator inbuilt into alternator.

Check your grounds - ground issues are common on RENIX. Pay particular attention to cleaning the main engine ground lug (pax side, above & behind dizzy) and the chassis ground (driver's side, cylinder head-to-firewall. The engine end may be relocated to the rearmost fuel rail mounting screw without incident.)

Also, verify any and all suspect voltage readings yourself with a known good multimeter. The IP voltmeter on RENIX is a notorious liar, and should only be used for a "state-of-charge" indicator.

I'll pull the grounds and clean them up. I have a new webbed strap for the chassis ground. The guy at the store said there would be no performance gain by using a thicker copper/coated cable- does that make sense?

After that it sounds like a new alt.

Thanks guys!

Seriously!! Check and replace the grounds. I have an 89 that did the exact same thing. Replaced the alternator and did nothing! I finally listened to 5-90 and added some 2 guage grounds all around the engine. The one that seemed to help the most is adding a ground from the negative to the radiator support. Make sure it is bare metal and no paint left! Also that POS braided ground to the bolt on the firewall to the bolt on the back of the valve cover has to go! Don't listen to those autozone guys! Probably never experienced the renix issues before!!

HenryKrinkle said:

I'll pull the grounds and clean them up. I have a new webbed strap for the chassis ground. The guy at the store said there would be no performance gain by using a thicker copper/coated cable- does that make sense?

After that it sounds like a new alt.

Thanks guys!

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Using a heavier cable allows for better power transmission with less conductor loss. Also, using a heavier & cleaned-up ground allows for a more reliable ground reference - which means the engine sensor signals are cleaner.

Since the ECU is grounded to the chassis and the sensors are grounded to the engine, a solid ground plane becomes critical. I also tend to recommend adding a direct ground from the chassis to the battery as well - it helps!

Improving your electrics isn't necessarily a performance mod in and of itself, but it can compliment other performance modes (particularly ignition improvements,) and allow for an improved electrical source - which helps, period.

I wouldn't go so far as to say that improving your mains would benefit engine output on its own (it can, but it's unlikely,) but it will help with a number of things, and it certainly can't hurt!

Thanks again guys,

I pulled the main ground out-
The coating is cracked badly and I have about 2" worth of exposed copper wire--VERY ugly.

I'll go get materials to replace it and the main red one too. Is 4 guage ok or should I find 2 ga (only 2 accessory lights, no winch)?

Also, I tried to track down the alternator's wiring. I think that goes to a "power distribution center".

Should I replace the wire running from the alt to this thing and the wire running from this thing to the battery? What guage?

Could a bad power distribution center cause my no-charging?

Thanks for any help!

4 gauge is enough.
bond the alternator case to the passenger side fender.

clean up the positive cables and replace if they look suspect, otherwise leave them be.

I have a new 4 ga. main ground to B- and replaced the webbed strap with 4 ga. as well.

Should I also ground the alt to battery and battery to fender?

What about the wires coming out of the alternator-- my Haynes manual says it should be blk/gry going to the power dist center-- should I get 4 ga. for that too?

PS- No change on voltage situation so far (probably still need new alt) - I do like fixing up the wiring though- any more suggestions?

HenryKrinkle said:

I have a new 4 ga. main ground to B- and replaced the webbed strap with 4 ga. as well.

Should I also ground the alt to battery and battery to fender?

What about the wires coming out of the alternator-- my Haynes manual says it should be blk/gry going to the power dist center-- should I get 4 ga. for that too?

PS- No change on voltage situation so far (probably still need new alt) - I do like fixing up the wiring though- any more suggestions?

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Thread title says Renix, but you keep mention a power distribution center, which Renix does have (at least not like the HOs have). What year is this beast?

'88- I might not have the name right on that part. This is a small unit with one main bolt that has 6-8 wires on it. One looks like it comes from the alt, one goes to B+, the rest seem to spread around.

This thing does have a body, so maybe it does a little more than just gather wires and maybe could fail.

Is there a fuse coming from the alternator that could cause this problem?

I have no issues running and driving except charging.

Planning on leaving in a little while to get a new 100 amp alt from one of the chain stores...

That is a starting relay, very old style relay.

I am 99.99% you need an alternator. Most parts stores can test the alternator.

All the lead contact surfaces on that relay could probably use a good cleaning by now, if you have not already done that. I am not aware of any fuses between the battery and alternator. 99% of the time, low voltage, like you described is the alternator gone bad.

Thanks all- new one is almost done- just can't figure out torque specs for the older mount style.

I found the specs for the newer ones that use the alt to adjust belt tension- mine uses the power steering.

I can't find anything in the FSM, so I'll probably just give them the 18 and 28 called for the later models and be done with it...

Unable to edit my last post, so I'll update in this new post:

New alt in--- key on, volts read 10ish - running motor reads 14. No real surprise thankfully. One minor surprise is my in-dash volt meter seems to work pretty well.

Thanks for all the help!

Ecomike said:

I am not aware of any fuses between the battery and alternator. 99% of the time, low voltage, like you described is the alternator gone bad.

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I have not looked, but is there not a fuseable link on the alternator output?

HenryKrinkle said:

'88- I might not have the name right on that part. This is a small unit with one main bolt that has 6-8 wires on it. One looks like it comes from the alt, one goes to B+, the rest seem to spread around.

This thing does have a body, so maybe it does a little more than just gather wires and maybe could fail.

Is there a fuse coming from the alternator that could cause this problem?

I have no issues running and driving except charging.

Planning on leaving in a little while to get a new 100 amp alt from one of the chain stores...

Click to expand...

That would be your starter motor relay, and the "wires" come off of it (that don't go to the battery) are actually fusible links for main power distribution.

I'm not sure if the relay itself is in the aftermarket - I got tired of buying them OEM, so I left the thing in place for the power distribution and bypassed the starter motor relay proper with a regular DIN relay. It's doable, it's fairly easy, and I haven't had to replace it since (I did the DIN bypass the fourth time I lost the starter motor relay one summer...)

@Hypoid - yes, there is a fusible link in the alternator output lead (6AWG lead, 10AWG fusible link wire. Good luck finding the stuff - I usually replace it with an ANL fuse.) It also runs to the screwpost on the starter motor relay.

@OP - that 10VDC with the vehicle at rest - is that Key ON Engine OFF or Key OFF Engine OFF? If the key is ON, what all is running electrically? That's an awful lot of drop - nominal resting voltage is 12.6VDC, with an acceptable range of 12.2-13.2VDC. You may be looking for a draw.

14.0VDC for a system running voltage is just fine - acceptable for that is typically 13.6-14.5VDC.

That 10 was key on, motor off and was just a dumb guess using the in-dash gauge. Mine has 14 in the center, then red to the left side between 12 and 9. It was into the red a little. Probably really at 12 as the battery is brand new.

Thanks again!