Alternator or Something else.... '89 Renix

[Archaeor]

The truck sputtered then died.  It turned over slowly a few times, but battery was dead and wouldn't start.  Got a jump and made it home.  Trickle-charged the battery for a few hours and now it starts, but the alternator is only putting out 9-10 volts according to dash meter.  Is my alternator shot, or could it be something else like a loose wire or connection?  Thanks.

 

Rick

[87MJTIM]

Don't trust the dash gauge!  Mine constantly reads low.

[Hippie66]

Get a cheap digital volt meter to check it. Should have 13.5 to 14.5 at an idle.

[Archaeor]

The gauge used to read a solid 14 volts........

[Hippie66]

Don't trust it.

[Minuit]

The voltmeter on a Renix truck is... uh, I believe the technical term is "a lying sack of $#!&" Sometimes my '89 reads 14 when the truck is idling and other times barely out of the red. Alternator is fine in it confirmed by three different multimeters. It's literally less useful than an idiot light. Check the alternator output with a real multimeter and report back what you find.

 

The sensing lead can be relocated to a cleaner source of power if you so desire.

[cruiser54]

http://www.cherokeeforum.com/f2/battery-starter-alternator-test-78125/

[SVPete]

Funny, I've trusted the voltmeter in my truck for 29 years and I still always believe it.

[Green Mesa XJ]

Yep the factory gauge I wouldn't trust as gospel, although mine on the 85 XJ would always read too low but did give me warning if the alternator quit. Just swapped in 86 engine harness and new dash harness last year now the gauge is damn near accurate.

 

 

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[Crash]

Confirm charging voltage with a DVOM. If 13-14, then wire/ICP issue.

[Gene]

Dead battery + trickle charge for a few hours= almost dead battery.

 

A dead or defective battery will pull system voltages down. 

 

FULLY charge battery, see if it reads about 12.8 volts, then check the rest of the system

 

Gene

[87MJTIM]

My experience the gauge:

 

A little over a year ago, I was drive on a cold, rainy day with the lights on, wipers running and the defrost running.  Everything that could be on, was on.  I looked at the gauges and just about freaked out!  My volt meter was reading 10 amps.  I started turning off not critical electronics: radio, defrost (opened side vent windows) and head lights (left on running lights).  The gauge rose up to approx. 11.  It still had me worried.

 

When I got back, I tested the battery with a volt meter - 14.8.  The gauge was still reading about 12-13.  I stopped trusting the gauge.

 

I purchased one the Renix Engine Monitors (by Nick).  One of the displays is the voltage.  It reads a steady 14+ despite what the gauge reads.

 

Don't trust the gauge!