I am currently battling a problem with my 1985 Dolphin RV w/ 22RE Motor & Toyota Truck Cab. If it is left for more than a couple days, it will kill the battery. Nothing is on.
Also, the charge lamp is on. I replaced the alternator and was told by the tester it did not work at all. I get about 12.5v out of the alt sometimes. Other times i will get around 14v. I think this is due to the coach.
On the drivers side fender, I have a silver box (think ford starter solenoid), with three terminals on it. When looking from the driver side, the left (grille side) has no wire attached. The Middle has two wires, one comes from the alt, the other goes into the truck harness. The right (firewall side), has one, that goes through a circuit breaker, and into the coach I assume. I think something is wrong with this setup, I am going out now to disconnect the coach and see if the light turns off.
A bad alternator is probable, or it isn't wired up right - With the engine running above 1800 RPM at fast idle (or while driving) you should see roughly 13.5 to 14.5 volts at the battery terminals, depending on the outside temperature (hotter = higher). That's the proper float-charging voltage range.
If you are seeing 12.5V or below at the battery you aren't charging enough and are most likely using power from the battery.
See if you have 13.8V at the alternator output stud at the same time
- the fusible link on the cable between the alternator output and the battery could be blown. The fusible link is a 6" chunk of special wire spliced onto one end of the cable that acts as a fuse if there's a short circuit, like when a wayward wrench shorts the output stud to chassis ground.
The silver cylinder is a continuous duty (*) high current (*) relay (also called a solenoid or contactor) that charges the coach deep-cycle battery when the engine is running, and isolates the coach battery power from the starting battery power with the engine off.
(* - 'Continuous duty' is an important detail if you ever have to replace it. Use a standard "Ford Starter Solenoid" that looks just like it and it will overheat and burn out, almost certainly in under an hour. More like fifteen minutes would be my guess, and it would get hot and stink before that. And 'high current' meaning the power contacts are usually rated at 100A+ continuous.)
If there is no wire on the big stud on the left (as you describe it) I bet that's your problem - someone didn't understand what was going on, and mis-wired the relay. The wire from the alternator output stud is NOT supposed to be on the same relay stud as the coil power wire going to the ignition of the truck...
This would effectively hot-wire the ignition circuit so the truck ignition doesn't shut off - but even with a spark the engine will still stop when the EFI cuts off the fuel supply, so you wouldn't notice it. It would also explain the starting battery going dead, because of the current drain from the ignitor module staying on...
The only other possibility is they got a batch of oddball relays for cheap and didn't use the industry standard Single Pole - Normally Open relay.
Charge Isolation Relay Functional Description:
The left side of the relay should be a large copper stud (5/16" or
3/8" threads) and that's supposed to go to the truck starting battery
terminal - but the alternator output stud works too, the factory cable on the alternator goes through the engine harness and straight to the battery, probably with a fusible link.
The two small studs (8-32 or 10-32 threads) in the center of the relay will go to the relay coil, or if there's only one small stud the other end of the coil uses the case ground to the truck chassis - make sure that the case is properly grounded with tight mounting screws, and that the fender itself is properly grounded.
The right side large copper stud relay terminal goes to a 30-Amp self-resetting thermal circuit breaker, and then eventually to the coach deep-cycle battery + terminal.
Errata:
Dolphin (National) usually tapped the isolation relay coil power off the ignition circuit hot wire, so it won't be left on with the key in the "Accessory" position. The two batteries need to stay isolated so you don't run down the starting battery with the overnight coach loads
- inside lights and the furnace blower.
And don't run the dashboard radio all night unless you have someone rewire it with a switch to run off the coach battery when parked. The starting battery is not a deep-cycle type, and can be ruined in under a dozen deep cycles, like leaving the headlights on all night.
I didn't know the relay on the side had anything to do with ignition. So you say the truck batt should be connected to the post on the grille side, the coach to the post on the right side. Does this mean I connect the alternator to the middle post? They all look identical. I don't think the unit is bad.
It does not, Dolphin added it - but they tap into the ignition power circuit going into the ignitor and coil system to power the relay coil, so it is energized only with the engine running.
Depends on if it's a three-post or four-post. First, let's make sure we're discussing the same thing...
See if your relay looks like this manufacturer's "Cut Sheet":
formatting link
safe 476Kb) There are other companies making the same design relays, some overseas for cheap. But if you'll pay a few dollars more this is a known quality source - Allied Electronics stocks them.
formatting link
The two big posts 180-degrees apart are the power contacts in the relay - one side to the truck battery + post /or/ the alternator output stud, the other to the circuit breaker and back to the coach battery.
The small posts in the middle are the relay coil - two posts (Type
3A or Type 4) and one needs to be jumpered to a ground point.
If you only have one center post means it's case ground and the mounting point needs to be grounded - and you don't have a Stancor relay, since they don't make a case-ground model...
NOTE THE NOTE at the bottom of the page: You have to use two wrenches when working on this, if you don't hold the back-up nut you can twist the contact in the case and destroy the unit.
Disconnect the positive post of your starter battery, Between the post and cable install a inexpensive VOM set on high AMPS. Disconnect fuses one-at-a-time to see which causes the current leak to stop, and in this case, also disconnect the incoming hot wire from your battery isolater (or generator, etc.). Repair or replace the "bad" connection/ component. It's slow but accurate, and you may find other RV components "leaking" current as well (heater, etc.). Good luck.
We are not talking about the same thing I'm afraid. I don't think my ford starter solenoid analogy was accurate, a friend told me that was what it looked like, i assumed ford solenoids were like that (Hey, I'm a toyota guy).
Oh sh*t, that's not a relay isolator, that's a diode isolator!!
I didn't know Dolphin switched over. Or someone tried to upgrade it themselves and got it wrong... The best company for these is SurePower, and NAPA carries them.
formatting link
You need to leave the "To Alt" cable on the middle stud, and move the "To Truck Batt" cable to the vacant end stud. And make sure the power diodes haven't gone open.
There are two big power diodes under that black potting - Hot in the middle, out at the ends.
And I'm betting whoever did this got it wrong, because many newer alternators (Including 85 and later Toyota) fall into "Group 2" and need a fourth wire from the diode isolator to the output voltage "Sense" pin on the small alternator harness plug - go see the notes at
formatting link
If you don't hook up the Sense pin to the starting battery so the alternator sees the actual battery voltage the alternator puts out
13.8V at the output stud, and then you lose 0.7V to 1V going through the diode in the isolator - and the battery never gets up to full charge.
The sense pin input says "Bump it up - the battery only sees 13.1V!"
And when the starting battery didn't charge right, they put both wires on the same stud and effectively bypassed the isolator to the starting battery - and now the coach battery won't charge enough from the alternator...
Okay, I moved the studs as you said. But now I am facing a new problem. The charge light is now off, except when I turn something on. When i push the brakes, they come on. When I turn on the lights, they come on. It flashes with the blinker. You mentioned something about a wire that would have the alternator sense a "correct" voltage? Could you please guide me through wiring this up?
Just another Update. I researched it a bit and I think that I should splice in a wire from the center (alternator) terminal of the isolator, to the top (see diagram) pin of the plug. Someone let me know if this is right.
It sees that the voltage coming back on the control wires is lower than what's leaving on the Output lead to the battery, and that trips the charge light.
If the alternator in the truck is the kind that needs the external voltage sense wire to put out the right voltage, you have the wrong diode isolator - the fourth stud on the isolator is connected to a third diode inside the potting compound, and the forward drop of the diode (roughly 0.7 volts) fools the alternator into boosting the output voltage by the same amount to compensate. Then you get the
13.8V you need /at the battery terminals/ to fully charge the battery.
Go to a local auto electric rebuilding shop that really knows their stuff, and they can tell you. Or make a webpage with a few close-up pictures and give us the URL address, and tell us the model numbers stamped on the alternator case - one of the regular posters here used to rebuild alternators, and he'll know from memory.
If you have to buy the 'right' diode isolator to get the sense diode output, they're not cheap but not killer - $50-ish. If the one you have was not damaged, someone with an older vehicle can use it. Older cars sense the voltage from the small alternator leads, and do the voltage boost by themselves.
Hello. I have a 1995 Dolphin Rv and I am having a similar problem. My battery is getting overcharged. As soon as I start the engine within seconds I can hear the battery starting to boil and acid starting to come out from under the caps! I instantly shut it down.I purchased a new alternator and had it tested. On the testing rig it read 14.3v. When it was installed in the motorhome I was getting 19.3 volts at the battery and on the voltage indicator on the Dash. Going to various RV forms, I am getting advice to look for external voltage regulators, loose or frayed wires, bad grounds, etc. A new development now is that the inside ceiling lights are not working! All of the fuses are good by the way. Please help! Why is the battery getting more power?!
battery is getting overcharged. As soon as I start the engine within seconds I can hear the battery starting to boil and acid starting to come out from under the caps! I instantly shut it down.I purchased a new alternator and had it tested. On the testing rig it read 14.3v. When it was installed in the motorhome I was getting 19.3 volts at the battery and on the voltage indicator on the Dash. Going to various RV forms, I am getting advice to look for external voltage regulators, loose or frayed wires, bad grounds, etc. A new development now is that the inside ceiling lights are not working! All of the fuses are good by the way.
I am not familiar with this particular model, but if the alternator is the type which senses the voltage through a separate wire to the battery and this wire has become disconnected, it will deliver the maximum voltage continuously.
If it is a 'battery sensing' type, the connector on the back of the alternator will have two big terminal spades and some smaller ones. One of these smaller ones should be connected directly to the battery positive terminal. Check to see that the wire or the end terminal hasn't become corroded where it goes onto the battery clamp and that the female connector at the alternator end hasn't become corroded or chewed up by mishandling.
In a motorhome, it is possible someone has messed up the system in their attempts to fit a second battery - in which case you will probably have to seek the services of an expert.
If all else fails, changing the alternator to a 'machine sensing' type will overcome this problem, although it could later result in low-charging problems if there is corrosion elsewhere in the electrical system (particularly in the earth braids, which are often overlooked).
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.