Fuse block driving me nuts!

[bkahler]

I'm really lost on this one. The fuse block inside the glove box on our 310 MH is a piece of cr*p

When we picked up the MH there were several plug in connectors that were melted or just plan missing. Two of the ones with melted wires were the dash air blower motor and the rear air bag compressor. I have yet to identify the 3rd wire that has the end melted off.

First the current (no pun intended!) symptoms:

After reconnecting the air bag plug and the dash blower motor plug and then going for a drive I found that the voltage reading on the dash volt meter was dropping down to as low as 10 volts . I then hooked my digital volt meter up and monitored it while driving. The voltage prior to starting the engine but with the ignition switch in the on position would start out around 12.5 volts and gradually start dropping. Turning on the dash air blower would cause the voltage to drop to around 11.2 volts and continue to drop. Even while driving and the alternator charging the results are the same. I've checked the voltage at the chassis battery and its 13.6 volts or so with the engine running. The problem appears to be in the dash fuse block somewhere. The other thing I noticed while driving around and monitoring the dvm was the voltage would sometimes bounce up to 13.5 for a short time and then drop back down to 12 or 11 volts. Those sort of readings strike me as being caused by a loose connection.

What I've done to try and remedy (or bypass) the situation is to rewire the air compressor circuit such that the wire going form the dash fuse block drives a small relay I installed near the compressor. The power for the compressor itself actually comes from the generator compartment at the starter solenoid. Much shorter run and is switched on and off by the relay that was added.

I also ran a 10 gauge wire from the circuit breaker in the engine compartment that feeds the two seat motor controls to a new fuse block I added in the glove box. That fuse block feeds the dash air blower via a relay installed similar to what I did for the air bag compressor.

It used to be when I turned on the dash air blower with the ignition switch off but the engine not running and I would see an immediate 1 or 1.2 volt drop on the wire feeding the blower motor. With the power now coming from the circuit breaker up front at most I see about a .4 volt drop. Much better and even sounds healthier .

However the dash fuse block still has problems. Most of the time the voltage reads around 12.25 volts and at times drops to as low as 11 volts and as high as 13.5 volts. No consistancy to whats happening.

Its my opinion that I have a loose connection somewhere, most likely in the feed wire to the fuse block. The problem is I don't know where that wire comes from. I have no way of reaching the back side of the fuse block without disassembling the dash and I can't seem to locate a chassis wiring diagram anywhere.

So, on the 1984 P30 chassis does anyone know where the wire comes from that feeds the dash fuse block? We're getting ready to make a trip a week from saturday and I'd sure like to get this problem resolved.

Any help would be greatly appreciated!

Brad

[Chaplain Kent]

Brad,
This is not going to be any help to you and maybe frustrate you even more but I fought the same thing as you are going through blowing fuse after fuse. I started buying them by the gross and when I realized that the entire fuse block was filled with 30amp fuses I knew it was time for a proper fix. This winter I had the chassis rewired, a new wiring harness and fuse box installed. When the technician first looked at the existing wiring he was shocked that it ever left the factory in that condition. However, in defense of Airstream, over the 25 years many things had been added, subtracted, changed, altered, manipulated, and screwed with. He started with a total rip out. The wiring schematics we have are no longer correct due to PO's and our own tinkering. Today I have this easily accessed panel of over 20 fuses, none of them ever blow, no wires ever get hot, everything works, and I feel really safe. By far this was the best money I have spent on my motor home to date.

[overlander63]

I don't know how electrically adept you are, if you think you can't do this, you probably should get a professional to look after it.
Install a new main feed wire from the battery to a replacement fuse panel. You can get these fuse panels from auto parts stores, or marine places like E&B. I recommend the marine ones with the brass connectors, as they don't rust. You can mount the new panel near the old one, and move one circuit at a time from the old fuse panel to the new one. There are two ways the fuses are powered, one by the accessory position in the ignition switch, the other direct from the battery. Check the power in the old fuse panel to verify which you are working on. It is important not to wire things that are "switched" direct to the battery, as this will increase parasitic loads, and drain the battery when the engine is off. Make certain you use the same amperage fuse in the new panel as there were in the old one.
The fuse panel you get will probably not be divided into switched and direct, if it is, then wire the switched fuses into the switched portion of your new fuse panel. When you are finished moving circuits, you can discard the old panel.
Let me know if I've made things clear as mud, and I'll try to clarify.

[bkahler]

Originally Posted by overlander63

I don't know how electrically adept you are, if you think you can't do this, you probably should get a professional to look after it.
Install a new main feed wire from the battery to a replacement fuse panel. You can get these fuse panels from auto parts stores, or marine places like E&B. I recommend the marine ones with the brass connectors, as they don't rust. You can mount the new panel near the old one, and move one circuit at a time from the old fuse panel to the new one. There are two ways the fuses are powered, one by the accessory position in the ignition switch, the other direct from the battery. Check the power in the old fuse panel to verify which you are working on. It is important not to wire things that are "switched" direct to the battery, as this will increase parasitic loads, and drain the battery when the engine is off. Make certain you use the same amperage fuse in the new panel as there were in the old one.
The fuse panel you get will probably not be divided into switched and direct, if it is, then wire the switched fuses into the switched portion of your new fuse panel. When you are finished moving circuits, you can discard the old panel.
Let me know if I've made things clear as mud, and I'll try to clarify.

Chaplain Kent, someday I'll do the fuse block conversion. Didn't want to tackle that just prior to taking our first official trip in the new MO... I found your old posts on the subject and read through them. You certainly had a challenge there for a while.

Terry, I'm fairly adept at electrical systems. I'm an automation engineer by profession.

Someday I'd like to do the fuse block conversion but for the time being (say a year or two) I would just like to get things working so we can use the mh safely.

I'm beginning to think that along with the poor quality fuse block that GM supplied with these motorhomes I believe I have a loose connection somewhere or possibly a failing circuit breaker.

With the engine off and monitoring voltage at a the chassis fuse block the voltage now seems to just bounce around going as low as 11 volts and as high as 12.5 or so. Turn the engine on and the voltage goes higher to around 13.7 and even 14.1 once in a while. But the longer you have the engine running the voltage finally stabilizes around 13.5 or so. Which makes sense because the alternator is doing its initial recharge of the battery after starting the engine. However it still bounces around and drops down to around 12 frequently.

We did a test drive this evening and when the road conditions were poor the voltage fluctuation was more rapid. On a good road there was still fluctuation.

So I guess tomorrow I will disconnect the batteries and crawl in and under the coach to check and tighten all the electrical connections I can find. I do know I need to replace the 3 circuit breakers in the engine compartment as they are badly rusted. I'm hoping to get to that on Sunday or Monday.

I'm now wondering if these fluctuations are causing the problem with my brake controller installation. I wired in the brake controller yesterday and have one major problem as yet. When I hook the green wire into the brake pedal switch it doesn't work. When I disconnect the green wire and use the pushbutton on the controller it works as it should. There are 2 switches on the brake pedal, one with white and orange wires and the other with purple and green wires. I'm currently hooked to the white wire because when I checked prior to pushing the brake pedal I had 0 volts. When pushing the brake pedal the white wire goes to 12 volts. The only thing I haven't done is verify which switch is for the brake lights. I think the white and orange wires are for the brake lights and I will verify that tomorrow.

As a check to my installation I swapped out with a different brake controller that I had (known to be working) and got the same exact results.

The brake lights do work when pushing the brake pedal so one of those wires have to work.

Any thoughts on the brake controller issue?


Thanks,

Brad

[overlander63]

Brad, one of those switches turns off the cruise control. If you check the wires on both, only one wire should have voltage when the switch is open. The brake light feed wire should have voltage at all times, the switch for the cruise control, only when the key is on.

[bkahler]

Terry, if I remember correctly that would mean the orange and white wires are the actual brake light wires. If thats the case then I have the wiring hooked up properly for the green wire from the brake controller. Do you know if when the brake pedal is pushed should the white wire read a full 12 volts or something less than 12 volts?

Thanks for the info.

Brad

[overlander63]

Originally Posted by bkahler

Do you know if when the brake pedal is pushed should the white wire read a full 12 volts or something less than 12 volts?

Thanks for the info.

Brad

It should read "battery voltage" when the brake pedal is depressed. There are no resistors or potentiometers invloved.

[Alumatube]

Terry, I am just AMAZED at your depth and breadth of knowledge! That, and you willingness to share and help others. Thank you SO much for your help and suggestions!

Susan (Brad's wife)

[vswingfield]

Hi Brad and Susan,

I had similar problems with the fuses in my old TV, a 77 ¾ Dodge van. I too ended up running a separate 10-gauge wire to the AC blower. It sounds like you are on the right track in cleaning the connections. You may want to use something like CRC 2-26 spray or Ideal NOALOX (in a tube) anti-oxidant on the connections. Both are available at Home Depot in the electrical section.

On another topic, what was the result on your Coleman AC Gasket?

Enjoy your trip. Where are you going?

Vaughan

[flitzwhopper]

my buddy who is a mechanic made fun of me when I went entirely through the positive side of my car looking for a problem and then found out is was a bunch of corroded ground connections. The corroded connections provided enough resistance to put some unusual loads on the supply side voltages.

[bkahler]

Originally Posted by overlander63

It should read "battery voltage" when the brake pedal is depressed. There are no resistors or potentiometers invloved.

Terry, thanks for the info. That let me know I was connected to the right place.

I spent an hour or so checking the electrical connections and I found a loose nut on the solenoid that is used to bridge the coach batteries to the chassis battery. The loose connection was the one that has four large wires connected to it. I've been opening and closing the battery storage compartment a lot lately and that might have helped cause the problem. I tightened that connection and also loosened and then retightened the ones on the 3 circuit breakers in the engine compartment.

We then went for another test drive and the voltage readings stayed nice and steady. Only real fluctuation came whenever I pushed the brake pedal. At that time the votlage would drop about .4 volts and pulsate a little bit. Makes me wonder if there isn't a problem with the brake light wiring somewhere. I'll have to check into that, "real soon now"

I think I found the problem with the brake controller. While doing our test drive this evening I reach down and played with the connector on the green wire going to the brake switch. At that point the controller seemed to start working. So it looks like maybe I just made a bad connection while installing it. That didn't exactly make my day....... I usually do a pretty good job on connections like that.

Anyway, for the time being I'm calling the brake controller fixed and moving on to bigger and better things

Thanks for all your help.

Brad

[bkahler]

Originally Posted by vswingfield

Hi Brad and Susan,

I had similar problems with the fuses in my old TV, a 77 ¾ Dodge van. I too ended up running a separate 10-gauge wire to the AC blower. It sounds like you are on the right track in cleaning the connections. You may want to use something like CRC 2-26 spray or Ideal NOALOX (in a tube) anti-oxidant on the connections. Both are available at Home Depot in the electrical section.

On another topic, what was the result on your Coleman AC Gasket?

Enjoy your trip. Where are you going?

Vaughan

Vaughan, I'll try the Ideal NOALOX this fall when I plan on going throught he electrical system in more detail.

As for the AC gasket, I'm still waiting on it. I have a hunch they held the order until a part that was back ordered arrives. I need to call them tomorrow and find out for sure. I really would like to get that last gasket installed before we head out. Worst case I suppose I could just use the 14" gasket I have and cut it to fit like I did the other one.

We're going to Valley Forge, PA for the Vintage Triumph Registery convention. Every year the convention is hosted by a different club. We got married 5 years ago at the convention when it was held in Red Wing Minnesota at the Casino. Talk about a good time, we even made some money gambling.

Brad