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Howdy, I have a 1977 Mobile Traveler on a Dodge cutaway chassis. I am trying to identify a charging problem I am having, and see a part under the hood I do not recognize.
It looks like some kind of resister unit that leads to the "house battery". It has a good sized aluminum heat sink and is about the size of a voltage regulator. The terminals are exposed, and there is some kind of what looks like a multi braid resister wire mounted between two posts within the heat sink area. The lead from the alternator is soldered to one of the posts on the front of the unit. The lead to the vehicle battery is connected with a nut at the back of the same post, thus, voltage from the alternator to the vehicle battery does not travel through the "resistor" (or whatever it is!).
On the back of the other post, the lead to the "house battery" is connected. Thus the power from the alternator does travel through the "resistor" (or whatever it is!) before it heads for the "house battery".
There are no moving parts, and no electronic parts.
It was apparently installed by the motorhome manufacturer, as they screwed it to the firewall (with only one screw!) using the same "square head drive" screws that are used all over the place in the construction of the motorhome.
I should say that my description is how it used to look. In my search for the charging problem, I discovered the terminals on the back of this "whatever it is" were pretty corroded. In my attempt to take the nuts and leads off the back to clean the terminals, one of the posts twisted off internally, thus rendering this "whatever it is" useless unless I can solder it all back together.
I should also mention that there is a seperate electro-mechanical battery isolator which cuts off power to the "house battery" when the vehicle is shut off. So whatever this thing is, I would guess it has something to do with limiting/reducing/conditioning the alternator power to the "house battery". I have not been able to locate any kind of reference to it.
Anyone have any idea what this thing is? And if any more are available? Or what it can be replaced with?
Thanks in advance for whatever help you can offer.
Hi, What you're describeing is a type of rectifier. It's used in the charging circuit as an anti-discharge unit for your house battery. It lets the current flow back to the house battery, when your alt. is chargeing, but lets no charge out of the house battery back into the chargeing/starting loop. Rich
Thanks for the reply, Rich. I finally took the thing down to an electronics shop here in town to see if they had the parts to build something similar. Turns out you are exactly right in what it is.
Basically, it is just two standard, stud mount, industrial rectifiers mounted to an aluminum heat sink. I was mistaken about any kind of "resistance wire". Actually, what I was looking at was just No. 10 braided wire with the insulation stripped off so it could be theaded through the ring connectors on the tops of the rectifiers, and soldered into place.
I was able to replace the rectifier that twisted off with one just like it (except not rusty!) they had in stock, for about $14. Just had to do a little soldering.
Thanks for posting back. Glad you got it fixed so easy. It,s nice to know how everyone makes out with their problems, and I learn from what fixes their problem. 3/4 of figureing out a problem is knowing what works most often. Rich
It's all back together and the charging system is working again. I still don't know what the electro-mechanical switch mounted to the firewall next to the rectifier does. One fellow at an alternator shop here though it might be an "Emergency Bypass Switch", so I could start the engine with the house battery in the event the vehicle battery went low. He said if that were the case, I would find a push button switch under the dash somewhere, but I looked and have found nothing yet. So still a little mystery under the hood, but it's all working like it used to. I am leaving well enough alone (for now).
email Cary Nickel
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