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Old 06-04-2009, 10:00 PM   #1
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1982 28' Airstream 280
Venice , California
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Posts: 73
EMERG Help Pls: AC light on, no AC, no DC

I'm in a pickle. I returned to my Classic 280 to find the AC light on the panel ON. I am not connected to ac nor is the genny running. There is now NO DC power to any accessories. All the fuses in the rear under the bed are fine. I fear the Univolt has somehow failed, triggering the system to think it has AC power and cutting out the DC power from the coach battery in the process.

I'm heading out for a 5 day wedding trip in less than 2 hours. Or am I?

Please, any help. I owe you guys one...

Dale
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Old 06-04-2009, 10:02 PM   #2
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Sounds like a bad/shorted relay.
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Old 06-04-2009, 10:03 PM   #3
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Relay where? In the Univolt? External? C'mon...I need some constructive help here. Thanks...
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Old 06-04-2009, 10:11 PM   #4
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Sorry, I was trying to put out another fire. There isn't a relay as such in the converter. Later model coaches have a relay that looks almost like a older-model Ford starter solenoid, and sometimes they burn out. You should have 12 volts even if the converter turns into a pile of molten lava.
I'll see if i can pull up a schematic, so you at least have an idea where to look.

on edit, of course I can't find it...Look for a relay that looks like a solenoid, and try jumpering the two main wires. If everything suddenly comes on, as far as 12 volts, you at least know where you can look further.
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Old 06-04-2009, 10:17 PM   #5
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1982 28' Airstream 280
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Sorry, didn't mean to bite your head off. Rather stressed as you can imagine. The unit isn't actually a Univolt. It's a TU-550-6 Triad. Both batts are fully charged and everything has worked great for a long time. Nothing preceeded this. It truly came out of the blue.

My understanding is that the unit regulates the DC current as well as AC. So if it went south, wouldn't it take out the DC as well?

FWIW, I just fired up the Genny and it works fine. In fact, AC power switched on and all the Air Conditioning, Microwave, etc work fine.

I just have no DC power at all. Period.
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Old 06-04-2009, 10:18 PM   #6
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BTW, Terry, thanks for your help. If its easier, we can do this by phone.
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Old 06-04-2009, 10:24 PM   #7
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Originally Posted by dalefox View Post
FWIW, I just fired up the Genny and it works fine. In fact, AC power switched on and all the Air Conditioning, Microwave, etc work fine.

I just have no DC power at all. Period.
Okay, the generator started, which means, unless you started it with a rope, there is 12 volts, at least to the generator. I seem to remember there being a switchover relay near the generator inside that compartment, but I have nothing at home that gives me a picture I could scan and post so you know what to look for.

I'm hoping one of the forums' motor home owners checks in, they may have a pic for you.
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Old 06-04-2009, 10:30 PM   #8
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Dumb question: are both 50 amp fuses in good shape? Both + and -.
Also, if the Univolt has shorted, it could have drained the coach batteries. Try disconnecting the - cable to it, and start the engine. If you then have 12 volts with the engine running, you have a toasted Univolt. Unplug the 120 volt plug to the Univolt as well, so it can't drain the batteries. If you have a small battery charger, you can temporarily use that to keep some juice in the batteries until you can get a replacement.
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Old 06-04-2009, 10:56 PM   #9
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Good thoughts all. The genny, on mine at least, starts from the chassis (starter) battery. That is still providing 12v to the engine (which starts fine), the genny starter and the stereo. The problem I'm having is with everything that runs off the coach battery through the univolt. Namely water pump, all internal lights, etc. FWIW, both batts are well charged and checked with a meter.

And let's not forget that the panel shows AC Power ON, even when it's not. That indicator light comes from the Univolt. Looks like my Univolt shot itself less than one hour before we were going to leave.

I'm so horribly depressed right now. We've been planning this for two weeks. Is there any way to bypass the Univolt and draw my 12v directly off the coach batt? I can always recharge it by running the car and letting the Alternator do the work.
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Old 06-04-2009, 10:56 PM   #10
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BTW, yes, all fuses are in good shape. Both 50A as well as the ground fuse below. And all the other fuses that control the various DC circuits.
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Old 06-04-2009, 11:15 PM   #11
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Originally Posted by dalefox View Post
Good thoughts all. The genny, on mine at least, starts from the chassis (starter) battery. That is still providing 12v to the engine (which starts fine), the genny starter and the stereo. The problem I'm having is with everything that runs off the coach battery through the univolt. Namely water pump, all internal lights, etc. FWIW, both batts are well charged and checked with a meter.

And let's not forget that the panel shows AC Power ON, even when it's not. That indicator light comes from the Univolt. Looks like my Univolt shot itself less than one hour before we were going to leave.

I'm so horribly depressed right now. We've been planning this for two weeks. Is there any way to bypass the Univolt and draw my 12v directly off the coach batt? I can always recharge it by running the car and letting the Alternator do the work.
Yes, see post 8.

Quote:
Originally Posted by dalefox View Post
BTW, yes, all fuses are in good shape. Both 50A as well as the ground fuse below. And all the other fuses that control the various DC circuits.
Did you check them with a multimeter? They can look good, and still be bad.
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Old 06-04-2009, 11:21 PM   #12
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So let me be clear on this: the Univolt only has a couple connections: There's the AC plug that lets it draw power from the genny or shore power. And then there are three wires that go into the fuse box. Two are large gauge (+ and...?) and the other is a ground. Are you saying that if I disconnect the ground that all the DC accessories in the vehicle will draw their power directly from the coach battery and not through the univolt??? I did pull the ground fuse from the block and nothing changed. But I can try disconnecting the ground wire altogether...

Pls advise.

Also, what is the likelihood that an RV service place between LA and SF will have a Univolt in stock? I may have to head out and get this replaced on the road. Seems a very simple labor job...less than an hour. It's really an issue of finding a suitable unit on hand...
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Old 06-04-2009, 11:27 PM   #13
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Quote:
Originally Posted by dalefox View Post
So let me be clear on this: the Univolt only has a couple connections: There's the AC plug that lets it draw power from the genny or shore power. And then there are three wires that go into the fuse box. Two are large gauge (+ and...?) and the other is a ground. Are you saying that if I disconnect the ground that all the DC accessories in the vehicle will draw their power directly from the coach battery and not through the univolt??? I did pull the ground fuse from the block and nothing changed. But I can try disconnecting the ground wire altogether...

Pls advise.

Also, what is the likelihood that an RV service place between LA and SF will have a Univolt in stock? I may have to head out and get this replaced on the road. Seems a very simple labor job...less than an hour. It's really an issue of finding a suitable unit on hand...
Yes, I was on the phone with a forums member that owns a similar coach, and he says to unhook the negative wire, and unplug the Univolt. That will isolate it. When the engine is running, there is a relay that engages to charge the coach batteries while you drive. He told me he encountered a similar problem with his coach, and eventually replaced with an Intellipower converter. As for a replacement, you will probably find aftermarket replacements, such as an Intellipwoer or similar units. It's an easy install, I replaced a Univolt in a 345 last week, it took about 20 minutes.
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Old 06-05-2009, 06:16 AM   #14
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Quote:
Originally Posted by overlander63 View Post
Yes, I was on the phone with a forums member that owns a similar coach, and he says to unhook the negative wire, and unplug the Univolt. That will isolate it. When the engine is running, there is a relay that engages to charge the coach batteries while you drive. He told me he encountered a similar problem with his coach, and eventually replaced with an Intellipower converter. As for a replacement, you will probably find aftermarket replacements, such as an Intellipwoer or similar units. It's an easy install, I replaced a Univolt in a 345 last week, it took about 20 minutes.
I would get a intellipower 9100 with charge wizard good for you batteries... and same to install as a univolt and less noise to
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