Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling Fan

My '94 RT/10 (38,000 miles) is illuminating the battery light and the A/C & cooling fan are not operating. I did some research on previous posts and seems the battery is a common issue in regard to the light coming on, but I didn't see much of a solution about the battery/alternator, A/C, and cooling fan failing together.

Thus far, I have done the following:

- Disconnected battery at the engine compartment and it read about 12.5 volts with a digital meter. I also put a battery charger on the lead to the battery and it read "charged" within 15 minutes of a 2 Amp trickle charge.

- With the Viper's battery still disconnected, I ran jumper cables from the power feed and hooked them to my F150. The Viper started on my truck's power (engine off and running), but the electrical problems still continued.

- The Viper's voltage gauge reads between 14 to 16 (depending on engine RPM). As the the engine speed increases while driving (say over 3,000 RPMs), the battery light will go out, but it will light back up if I turn the A/C on or when RPMs come down to idle.

- Also checked my fuse-links and they are good.

Indication to me is that the alternator is flaking out considering the battery "seems" good, however, I do not understand how this might cause the A/C and cooling fan problems. I'd like to have a consensus from your guys and get your opinion(s) before I replace the alternator.

BTW, any suggestions on where to get a replacement alternator?? Are the local retail auto-parts stores going to have what I need or should I order from Summit Racing, Jeggs, etc.??

Thanks in advance for the replies!

I pulled my alternator off thinking it went bad and I'm a 30yr ASE tech. Good thing I tested it on my bench with OHM meter and took it apart and checked the brushes. I felt REAL dumb because I assumed and didn't test it on the car. 1st make sure you have battery volts to the alternator + wire when on the car and wiggle the wires where they come off the jumper post by the fuse box under the hood. It turned out that 6 " away from the jumper post is a main feed connection (wire splice)for alternator and fuse box and mine was corroded and burnt with a loose connection. It kept going intermittent. At the time it happened I was 30 miles from home and just made it back to my garage. Could be the feed to the fan relays too,

I think it's a connect like I just described because the alternator won't effect the fans if you have battery voltage.

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Thanks for the reply, it gave me something else to inspect, but all that seemed ok.

I checked the voltage at the alternator post and the battery terminal post, both read about 14.5 volts with the car running. I also checked the connection on the PCM, the connection below the heater blower motor, and the connection at the front/passengers side of the engine block. All those connections seemed nice & tight, and I pulled them apart and did a visual inspection as well. This is really putting me at a dead-end.

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Give Chuck Tator a call. He will be more than glad to give you his input on the possible problem. He helped me when I had problems with my 94 starting. And if you need any parts he can supply them with a 20% VCA discount in a hurry. He's been a lifesaver to me here in the middle of nowhere when it comes to getting problems solved on a Viper.

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

You can "borrow" my alternator. We'll know very quickly if yours is bad. The '97 and '94 both have the same alternator(part#4848662).

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Doesn't anyone else think 16 V is too high? My radar detector has a built-in voltmeter than beeps when it gets over 15.2V (which happens momentarily when the AC is first turned on.)

Saying the obvious to someone that has the smarts to look for this kind of problem, but the relays and AC always have 12V and it's the PCM that provides ground to complete the circuit. So having power is good, but to come on, the PCM has to flip that switch.

You are getting no fan at all, or just not high speed fan because the AC isn't coming on?

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Yeah, Chuck has helped me out on several occasions.

I spoke to him earlier in the week and he gave me most of the suggestions I posted here. I really didn't want to use any more of his time on this until I felt I exhausted every option, or making another parts order, thus my post here.

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

sounds like a grounding problem to me.

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Doesn't anyone else think 16 V is too high? My radar detector has a built-in voltmeter than beeps when it gets over 15.2V (which happens momentarily when the AC is first turned on.)

Saying the obvious to someone that has the smarts to look for this kind of problem, but the relays and AC always have 12V and it's the PCM that provides ground to complete the circuit. So having power is good, but to come on, the PCM has to flip that switch.

You are getting no fan at all, or just not high speed fan because the AC isn't coming on?

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No fan at all. I hooked an external power source to the fan leads and it powers on low and hi, so the fan is good.

I'm not sure what is considered too high. I would expect the charging voltage to be a couple of above battery voltage...but at what voltage level it becomes a problem I don't know. With the voltage at 14.5 at idle, that should be acceptable, unless over-voltage can damage something...

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Well, now you need to find someone that is a contortionist and see if you can test the connections to the relay. On the fan motor side, the relay should have 12V all the time to it (and a wire going off to the fan that is switched), 12V to the switch side anytime the key is on, and the ground side of the switch is grounded when the PCM says to do so (engine is warm or AC is on.)

Does the battery light come on if the fan relays are removed?

Do you have a service manual with electrical diagram?

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

I have a spare alternator.

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

After I tested all the relays and wiring on the passenger's side kick panel (tested good), I then checked the 3-wire feed line that runs from the alternator. No power was coming out of the alternator on the gray wire that feeds the A/C clutch relay. Once I unpluged the connector from the alternator, my battery light on the instrument panel went out too. Then I connected 12 volts to the connector (gray wire) and the A/C came on and fan kicked on.

So it looks like it's going to be the alternator. Earl, let me know what you want for your spare. Thanks!

Just curious, is it usual in other vehicles for the alternator to supply a seperate hot feed to the A/C & fan(s)??

Glad I found my trouble, I'll be able to sleep better now! Thanks again for all the input guys!!

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

So it looks like it's going to be the alternator.

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Well, guess you will not be using mine now.

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Just curious, is it usual in other vehicles for the alternator to supply a seperate hot feed to the A/C & fan(s)??

Had Dodge vehicles all my life, including ex-police cars and conversion vans with trailer-tow high amp wiring and never saw that.

On the other hand, we are talking about a ~15 year old electrical design...

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

Well, guess you will not be using mine now.

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Knowing you Ted, you probably swapped out alternators while I was at work - oh wait, you'd first need the tools PLUS the mechanical ability to be able to accomplish such a task...so nevermind lol. Although, that would be the perfect explanation as to why it failed in the first place...because it came off your GTS! I'll be over in a few minutes to get my RT/10 alternator back! lol!!

Re: Bad Alternator?? Electrical Issue - Battery Light On, No A/C or Cooling

I guess if my car broke down as much as yours, I'd have the superb mechanical abilities that you posess.

This is exactly what is going on with my 1994 RT 10. I have removed the alternator and had it bench tested; all okay. Pulled battery and it showed 840 cold cranking amps. Relays check okay on bench. Jump 12 volts and a good ground to radiator fan motor and both speeds function great. What did this turn out to be? Also, when I switch on the A/C, the battery warning light comes on. Neither the A/C compressor clutch nor the radiator cooling fan will come on. Please help.

How was it bench tested? We have generators not alternators.

He would not allow me to follow him to the bench area. Reputable shop.