IVOLT?electrical questions. Please help!

[chasgould]

Hi Guys,
I am new to this list, having recently purchased a 1976 Airstream Argosy Motorhome, which is a nicely preserved, and unmolested example. Unfortunately, there are a number of electrical gremilins which I must chase away. I am certain that many of you on this list have dealt with these faults, and can likely save me considerable time and energy. So I would greatly appreciate any advice or suggestions.
Problem number one is that none of the 12 volt interior lights or accessories work off of the coach battery. They will work off of the chassis battery if the ignition switch is turned to the "accessory" position, but will not work with the switch in the "on" position, or with the engine running. This symptom is the same whether or not the unit is plugged into a 110 volt AC line. I suspect that the IVOLT unit is not properly converting the 110 volt to 12 volt, either for lights and accessories, or for battery charging. The unit (which I think is the IVOLT unit) which is mounted in the wall behind the rear bathroom closet is humming, which I think indicates that it is working. All of the fuses on the panel next to this unit are intact and not blown.
Are there other hidden fuses, as it appears as though the coach battery may not even be attached to the interior electrical system, which leads me to suspect a blown fuse or something similar.
How can I test whether the coach battery is connected to the unit properly, and whether the IVOLT is charging either, or both, batteries? Also, is this the IVOLT that I have described, or is this a separate battery charger, and is the IVOLT unit somewhere else? If separate, where do I find the other one? Is there a hidden battery isolator that I am missing somewhere?
In summary, the interior 12 volt lights will only work with the key on "accessory".
The second problem is that the ignition switch will not activate the starter. The key works to the "on" position, but when I turn it to the "Start" position, there is nothing except the "brake" light illuminates on the dashboard. So, I must go out and jump the relay wire to activate the starter. A previous owner did add a small 20 amp horn type relay to the starter circuit presumably to prevent battery draindown, and it is this relay which I must jump to activate the starter. I cannot tell if the relay is bad, or if the leads to the relay are not carrying current when the key is truned to the start position.
The question is how to test this relay, and what to replace it with, if it is bad. Also, should I eliminate this relay altogether, or is it a good modification to prevent battery draindown?
Please respond here or to my email at chasgould@aol.com
Thanks in advance for any help. I really appreciate it.
Chas

[thenewkid64]

As a Prior owner of an unmolested 76 I can offer some pointers.

1: Are both batteries good? There will be 2 batteries under the hood at the far left corner. Normally the front one is the starting battery and the rear is the house. Be careful pulling them out as you don't want to arc or get acid on you. If the house battery is dead it could be part of the cause of the 12 VDC lights not working.

2: If the univolt is humming that means it is running, not necessarily working. I would check with a volt meter to see if you have 12 Volts on the lugs of the univolt with a known good battery installed. Does the AC light on the control panel in the kitchen light up?

3: The 2 systems are supposed to be completely separate. There is only one cross connect and it is a boost relay. This is a little button that is covered with a rubber bootie on the dash. It is OEM. If the PO (prior owner) added a battery isolator than you will have more wires to trace down. Normally the battery isolator is a square thing, 3 lugs and is red or blue or silver finned.

4: Under the hood in the middle is the boost relay. It may be covered by a small square cover. There should also be some 50 amp glass fuses there. If your house battery is not connected due to the fuse being blown then this is where you need to look.

5: Turning the key on should not make all of the 12 VDC coach lights work. Something has been wired to make this happen, I would assume it is under the hood near the OEM boost relay.

6: If the coach battery is a deader then it could have killed the univolt. It could also damage the Alternator if it is part of the charge side of the circuit when the coach is running. That is why I suggest you start there. The Univolt charges only the house battery, the engine charges the start battery.

&: If you rare having to jump the relay under hood to make the coach start then I would assume that the relay is bad, but check the input. This may be the boost relay I described, and if so it is normally only used to start the engine from both batteries as an emergency type thing. To test the relay all you need to do is put 12 VDC to it on the little input lug and see if it causes the starter to engage. If it does then you need to trace the current wire back and see what it is or is not connected to.

I have tried to make it simple, but start with the batteries and main fuses. Then move further into the system. It is not that hard once you understand how things are interconnected.

[chasgould]

Hi Brett,
Tyhanks for the input. This is very helpful. I want to clarify that the original manual actually states that turning the key to accessory will cause the ivolt to charge the engine battery, so it makes sense that the engine battery would illuminate the interior lights with the key in the accessory position, and also explains why it does not work with the key on "on" or "start".
I will check the other things that you have suggested. The last owner had run the motorhome with no battery in the coach position, and this may likely be what has caused the problem. Also, on my way home, I threw an alternator belt and the engine battery got drained pretty low, but has since been recharged, and the alternator is working fine now.
Is the humming box in the bathroom closet the IVOLT? Is there a separate battery charger, or does the IVOLT also charge the batteries?
I have found and checked the fuse in the front tray near the box you have described, and it is fine (50 amp). The box has a cover on it, and the PO had added a small fusable link and a 20 amp horn type relay, which does not appear to be working. If I jump the two leadson this relay, the starter lights right up, so either the relay or feed is faulty.
What is under that large sqaure box with the black cover in the front center section. Is it an isolator or a starter relay, and how does it work?
Thanks again,
Chas

[thenewkid64]

The thing in the box SHOULD be the jump start relay that ties the batteries together if you wish to use them both to aid starting.

The Univolt is the only 120 Volt charger and does not normally charge the starting battery, but if turning the key to the acc position gangs the batteries then they would all charge if plugged in.

[87MH]

On the starting issue -

You might also run a check on the ignition switch for a gremlin in the starting circuit.

I was having a similar problem, and a Forum Member suggested I check the Neutral and Park interlock (no help in my situation).

At this point, I'm convinced the problem is in my starter (ignition)switch.

Since it's time for a major dash/electrical overhaul, I intend to renew all of the front wiring. The motor/chassis electrical systems seem to be weak links on the Chevy chassis, especially with age, so I would have to suggest replacement of systems instead of covering up the symptoms with bandaids.