Starting Problem - Electrical

[dave1518]

I have a problem that has me a bit perplexed. The rig is a 1987 Super Chief on a Chevy P-30 chassis. Something has happened and I have no idea what it was but sure could use a pointer or two on where to look.

Normally the unit will start with no problem. On the last trip, coming home it started in the morning with no problem. Traveled down the road, stopped for a short break, and when the key was turned to start it, nothing...no power at all. Held the MOM switch and it started right up. Voltage on the gauges showed 13V, and the panel switch also showed approx same amount. All lights worked, etc.

Got home, parked in driveway and started to test. Turn on ignition, indications of power, turn key to start, single click..then all power dead. Hold MOM and power "returned" and could start up.

Pulled chassis battery, cleaned all connections, put it on bench charger overnight, took it in to Interstate, battery tests fine. Reinstalled into coach, same problem again and same solution, bump the MOM switch and it will start.
Turn it off, try to start, a click and then all power is gone...no headlights or any power. Hit the MOM switch and have lights and can start.

Maybe a high resistance problem on the starter? SO took a charged deep cycle marine battery and used jumper cables to connect to chassis battery...no difference in response..single click, no power. hit MOM and power restored and starts.

On this rig the chassis battery is wired to a solenoid on the firewall. There are two other leads on the same post, one of which goes down towards the engine..I've not gotten all the way under to trace it..On the other side of the solenoid is a lead that I assume does to the house batteries..this must be the MOM solenoid?

I am confused on where to go next..anyone have a pointer for me?

[RJay]

The 13 volt output from the alternator is low, it should be at least 14.5. I suspect it could be either the voltage regulator or alternator. I also suspect the starter solenoid. Normally the click would indicate a low battery but can also mean the solenoid. Since the battery has been checked and even substituted we can eliminate it. Try bypassing the solenoid with the regular battery only.

[Billieg]

You have a problem with either the starter or the connections on the starter. If it was the Alt. or reg. it would still start with a jumper battery and using all your coach batteries will really "shock" it into starting. I had the same problem with my coach and the connection on the starter was really corroded and the ground wire was almost cut in half. I first thought it was the windings on the starter or the solenoid but that wasn't it. If the connections look good have the starter taken out and checked. Good luck.

[RJay]

Bill,
I mentioned the alternator/voltage regulator as a problem with only 13 volt output from the alternator. It sounds like there may be two problems going on.

[Billieg]

Quote:

Originally Posted by RJay Bill, I mentioned the alternator/voltage regulator as a problem with only 13 volt output from the alternator. It sounds like there may be two problems going on.

My gauge reads 12.5 - 13 volts when running but a built in digital volt meter I put in shows 14 -14.5 so the gauge isn't always right. If it is really only 13 then he has a few problems.

[RJay]

Quote:

Originally Posted by Billieg My gauge reads 12.5 - 13 volts when running but a built in digital volt meter I put in shows 14 -14.5 so the gauge isn't always right. If it is really only 13 then he has a few problems.

Yes, but we have to be sure his works that way.

[wa8yxm]

Well... You have cleaned ONE END of both the positive and negative cables.. The battery end.

Have you cleaned the CHASSIS end of the negative cable.. Or the Solenoid end of the hot one (Positive)?

Keep on cleaning is my recommendation.. also, another trick you can use.

Take a DC volt meter,, (MY adjustable load tester set on zero amps is great htere, ti's the dual meter load tester from harbor freight)

Positive cable to the chassis, or engine block
Negative to the battery negative.

Watch it while partner attepmts to crank her up

ANY measurable voltage is a bad thing (Well, .01 is ok but on that meter not measurable)

[dave1518]

Quote:

Originally Posted by wa8yxm Well... You have cleaned ONE END of both the positive and negative cables.. The battery end. Have you cleaned the CHASSIS end of the negative cable.. Or the Solenoid end of the hot one (Positive)?

I had replaced the positive lead so knew it was not the problem, but the negative lead looked solid so left it.... but ...
That was the key...pulled the negative off of the frame and cleaned it up..there was just a touch of corrosion present but that is all it took. Cleaned the connection

After that, all of it made sense...when you hit the MOM switch and pull in the coach batteries, they have their own ground connection so things would work, and when it started, no need for the battery to run...

dave W0LIV

[troth]

Dave, I had an '88 and went thru similar frustration. Take the solenoids off the wall in the house battery compartment and clean the connections, then reassemble. Same goes for the house battery cables at each battery, and the big ground terminal on the wall. Somewhere there's a dirty connection.
At least that's what helped when it happened to me.
troth@cmh.net

Tom