Motorhome Windshield Sealant Sought

We have a 32' HR (Monaco) Ambassador. It has a two-piece windshield. The windshields leak at the top intersection of the windshield pieces. It is not a major leak but I would like to prevent any water from getting inside. Could you give me the name of a windshield sealant to address a slight leak in the front windshield of our motorhome? What about silicone? Mike & Joanne H.  

Silicone sealants are generally classified as acid-curing or moisture-curing. Acid-curing sealants are the most common as you’ll find them in the big box stores. However, these materials are considered somewhat low-performance. They're likely to not provide satisfactory results for the temperature extremes or weather that a typical motorhome may travel through. A better choice is a commercial-grade, moisture-curing silicone sealant, in a low to medium viscosity such as Dow 790. I’ve also had good luck with Permatex 81730 Flowable Silicone Windshield and Glass Sealer in most cases. In some rare instances, it is a little too runny. It all depends on the curvatures of the windshield and just where the leak is entering. I’d probably try the Permatex first and then look for the Dow 790 if it doesn’t work.  

AGM Batteries for Motorhome

I'm thinking my coach batteries may need replacing within the year. I asked my RV dealer whether AGM batteries are a good idea. Currently it has the older flooded cell type that came from factory, (two chassis batteries and three house batteries). The answer I got from my dealer was to stick with the technology it came with and not switch to AGMs. Just so you know, I have a 2004 motorhome with a three-stage charger. I’d be interested in your comments and advice. Also, we enjoyed your TV show. Any chance of hosting another one? Jon, (no city/state)

My comment Jon, (since you asked), is that I’m guessing your dealer does not sell AGM batteries but does sell flooded, wet cell batteries. My advice? Well I’m a strong proponent of the AGM technology. And since today’s motorhomes are so DC voltage dependent, I’m also in favor of having as much DC current on-board as possible, regardless of battery type. But I can just as easily argue for wet-cell technology as well.

Here are some arguments for switching to AGM batteries. First, they are highly resistant to vibration and shock; a plus for RV applications when you consider the jostling and bouncing the motorhome does on the road. Their recombinant gases are effective to about 99%. What this means is that the hydrogen and oxygen are recombined inside the battery safely within each cell. Ever notice the bubbling and off-gassing of a lead-acid battery while under a severe charge? Most AGM batteries vent hydrogen vapors at less than 2%, where 4.1% is needed to support flammability in air.

The inherently low internal resistance of an AGM battery is another welcomed benefit to RVers who store their motorhomes part of the year. According to one maker, during storage, the self-discharge rate of an AGM battery is 3 to 10 times better than a gel battery and almost 50 times better than a typical flooded lead-acid battery. The reason is because the electrolyte is not liquefied, but rather absorbed into a floss-like glass matting. AGM batteries also deliver and receive current much faster and at the higher rates available today. Your three-stage charger will suffice nicely and adapt well for AGM batteries. As an example, AGM batteries can be charged 10 times faster than a same-rated gel battery and 5 times as fast as a like-sized flooded lead acid battery.

Because AGM battery technology permits more positive plate material to be saturated by the absorbed mats in each cell, there is an automatic increase in the battery’s capacity in virtually every area. More life cycles, reduced internal resistances, higher amp-hour rating in some cases, more reserve capacity and deeper depth of discharge cycles are some of the improvements over other types of sealed, lead-oxide batteries.

Yeah, I like ‘em! So if your wallet can endure and you consider yourself a “serious” RVer, then I’d truly consider the upgrade when it’s time to replace your existing batteries. 

Thanks for the comments regarding the television show. Currently we are ready to go with a brand new TV show, but we are awaiting sponsorships from the manufacturers and campgrounds. I’m thinking it will be a long wait, given the state of the industry right now. But we are set to go as soon as the advertising dollars can be raised.

Two Motorhome Air Conditioners

I have an older Pace Arrow that has two roof air conditioning units. The front air conditioner will not run (fan or compressor) on shore power. When I start the generator the front unit will work as normal. Any suggestions? Lost for answers! B., (Aiken, SC)

Well Bruce, it’s apparent your motorhome is equipped with only a 30-amp shoreline service. Having a 30-amp limitation basically means that you can only operate one air conditioner at a time while connected to shore power. The reason for this is that, on your Pace Arrow, each air conditioner must be on it’s own, separate 20-amp breaker. So in order to operate all the other 120-volt AC accouterments, you’re limited to only one roof air at a time. It’s simply basic math. 

However, there should be a set of switches somewhere inside your motorhome, (some technicians call them either/or switches), that allow you to choose between the front or rear air conditioner while connected to shore power. The generator, however, is sized large enough to handle both air conditioners at the same time. One air conditioner is hard-wired directly to the generator. On shore power, you must choose which A/C you want to operate. The switches can also be configured to run both A/Cs when powered by the generator (see illustration above). 

50-amp coaches do not have this problem since there are 50-amps available on two separate legs of 120-volts. On those RVs, each air conditioner is connected through a different leg. Again, it’s all in the math. 

If it is extremely important to operate both air conditioners at the same time, the only safe and code-compliant option is to install an aftermarket energy management system (EMS), which will automatically cycle each air conditioner, one at a time. Let me know if you cannot locate those “either/or” switches and we’ll dig a little further if necessary.

Charging 6-Volt RV Batteries

Is there a way to charge my two 6-volt batteries with a regular stand-alone battery charger? If so how would you hook up the positive and negative charger clamps?
George, (Fresno, CA) 

George, I’m going to assume you are referring to a stand-alone battery charger that is 12-volts only. I mention this because some shop chargers are equipped with a 6-volt output option as well as 12-volts DC. Since all DC components on RVs operate on 12-volts, (water pump, fans, lamps, etc.), your two, 6-volt batteries, as installed, are still set up to produce a 12-volt final output. The only difference is the connection between the two batteries. 

 
At the basic level, two 6-volt batteries are wired in “series” and two or more 12-volt batteries are wired in “parallel” in order to produce 12-volts final output. Take a look at the diagrams here; two, 6-volt batteries above and two, 12-volt batteries below. The final output that provides battery power to the components in the RV is still 12-volts DC. Therefore, both configurations can be charged by any 12-volt battery charger by simply connecting the charger’s red cable clamp to the “plus” 12-volt terminal lead and the black or ground cable clamp to the negative terminal as shown here. 

But a word of caution! Notice on the 6-volt battery diagram, you must know which battery feeds the positive voltage to the RV and which battery represents the negative connection. If your series connected batteries look similar to those depicted here, then all you do is connect them as shown. If yours are wired differently, do let me know and we’ll investigate further. Bottom line: 12-volts is still 12-volts. You do not want to connect either battery charger lead to the posts that make the interconnection between the two 6-volt batteries.