Looking for 12v in my 4108.

Chaz · February 10, 2007, 01:42:54 PM

Ok........ I have a heater that runs off engine coolant in my bus. It's a big black sucker with 3 fans. It has never worked and I am trying to figure out why. I'm pretty sure it has 12v fans but they had it wired down to the electrical panel in the first bay behind the entrance door. From what I can tell, it's all 24v in there. And where they had the wires connected, I couldn't get any voltage.
So where can I hook up to 12v for a heater?? The heater is mounted right above where that panel is in the first bay, so I was hoping to get it out of there. (but beggers can't be choosers)

Just tryin to get warm,
Chaz

Jerry32 · February 10, 2007, 02:13:56 PM

You could tap off at the 12V level as you shud have two batteries in series. so with a volt meter measure from ground to each battery and find out which one is at the 12 v level. then fuse a tap off from there. Jerry

larryh · February 10, 2007, 04:21:10 PM

Chaz

As far as I know from working on buses if it's 24 volt bus it should all be 24 volt somebody can correct me if I'm wrong.

LarryH

Jerry32 · February 10, 2007, 04:33:11 PM

You could always run a 24 volt inverter and connect it to a 12 converter .

Hartley · February 10, 2007, 04:38:28 PM

Quote from: Jerry32 on February 10, 2007, 04:33:11 PM
You could always run a 24 volt inverter and connect it to a 12 converter .

That's just GOOFY !....

The guy needs to locate the relay that operates the fans, That's all...

Sorry....

Dreamscape · February 10, 2007, 04:43:23 PM

Chaz,

Do you have an electrical schematic of your coach?

Make sure it is the correct one for your year and model.

If so you should be able to trace down the problem.

I finally got a good one for our Eagle and it sure has helped a bunch.

Hope you find your problem.

Happy Trails,

Paul

Dreamscape

DrivingMissLazy · February 10, 2007, 05:24:55 PM

Before you go looking for 12 Volts, you better find out what voltage the fans are.
Richard

frank-id · February 10, 2007, 05:41:38 PM

The GMC 4108 is a 24 volt bus. This bus is powered by 2 batteries of 12 volt. By connecting to just one battery, 12 volts can be utilized. On my GMC 4905 which is also 24 volts, the first battery was used for a source of 12 volts for interior lites, CB radios, and head lites. It will be an easy task to determine the fan voltage. Depending on the 12 volt power requirements, will determine all fusing and wire sizes. On my old 4905 GMC, a 50 amp buss or power strip was created near the drivers electrical panel. I have used 24 volt relays to control 12 volt loads. many years ago, it was rumored to require changing battery positions because of unequal battery loads. The change merely requires switching battery places in the battery compartment.
Most aircraft relays can be controlled by either 12 or 24 volts. With an increase of voltage, there is a decrease in amperage. Just like a seesaw..... Frank

Chaz · February 12, 2007, 07:23:57 AM

Thanx guys.
I was just hoping that there was a 12v line close to where the fans/heater are. Guess not.
I know there is 12v in the bus as I have 12v headlights and a cigarette lighter.

Thanx again!
Chaz

DrivingMissLazy · February 12, 2007, 07:50:26 AM

Quote from: Chaz on February 12, 2007, 07:23:57 AM
Thanx guys.
I was just hoping that there was a 12v line close to where the fans/heater are. Guess not.
I know there is 12v in the bus as I have 12v headlights and a cigarette lighter.

Thanx again!
Chaz

The 12 volts is a tap between the two 12 volt gbatteries that provide the 24 volts to the bus. Have you reallllllllly checked as to what the fan voltage is? I would almost guarantee that it is 24 volts. It would have been very foolish to put 12 volt fans in a 24 volt system. And especially since the wiring is run to a 24 volt only connection box.
Richard

H3Jim · February 12, 2007, 08:00:29 AM

Chaz, I just re read your original question. You say they had the fans wired in to a 24 volt box, but there is no voltage there. Sounds like a 24 v fan. Maybe there is a fuse or a relay thats out that will get that power going again. Rather than re wire, what about trouble shooting what's there.

QUOTE "Ok........ I have a heater that runs off engine coolant in my bus. It's a big black sucker with 3 fans. It has never worked and I am trying to figure out why. I'm pretty sure it has 12v fans but they had it wired down to the electrical panel in the first bay behind the entrance door. From what I can tell, it's all 24v in there. And where they had the wires connected, I couldn't get any voltage.
So where can I hook up to 12v for a heater?? The heater is mounted right above where that panel is in the first bay, so I was hoping to get it out of there. (but beggers can't be choosers)"

Chaz · February 12, 2007, 10:10:17 AM

Richard,
I would/will have to tear the fans out to see if there is anymore info on them, then what I can see- which is a long serial number with "12V" in the middle of it. Possible coincidence, but....
Plus, I found that only one of the three fans work. The whole "heater" was , shall we say - "Rigged" in there!

So it wouldn't suprise me at all. And as I said, where they had it hooked up, is dead. They may have fried the circuit breaker that it was connected to. All the other ones have juice.
I may run wire over from the panel on the drivers left (where the cig lighter is) and control it from there. I know there's 12v there. But I will tear out a fan motor to make sure it's 12v.......... but I think it is.
Thanx for the help!!!!!!!

gettin warmer,
Chaz

Oh!!!!!! p.s. by the way, I should be getting my 4024 Xantrex in a day or two, as I have word it was shipped today, so do you think it would be smarter to just wait for that and then do the wiring?? I'm getting pretty excited about it as I understand, once it's hooked up, it can make life allot easier!!

Tony LEE · February 12, 2007, 01:16:38 PM

Unless you have some sort of battery equaliser installed, running any significant 12V load from the centre tap of 2 12v batteries in series will eventually cause problems with the 24V charging circuit

H3Jim · February 12, 2007, 02:04:53 PM

and maybe you are thinking about it already, but a 12 volt motor can draw significant amounts of current. Way more than a mere cigaratte lighter or its wire can handle. You would likely need to rewire from the source with some beefy stuff that can handle the current.

I speculate that box might be 24 volts, lessening the requirement for wire thickness, but they had the 12v motors in series.