Another starting problem

Topic: Another starting problem (Read 2877 times) previous topic - next topic

Another starting problem

February 19, 2024, 03:06:36 pm

House batteries went low with cold weather(2 lithium pro batteries),removed from coach and charged and reinstalled,everything
in the hookup looks good,went to start coach after a couple of cold days and won't start.The 2 start batteries are fully charged,
you turn the key to the on position and the start relay energies for about 5 seconds the shuts off,after a few more seconds it comes back and repeats the process,this is the relay on the bottom of the panel by the stairs to the right of a similar relay,I
changed the relay,no difference,if you turn the key past the on position you get nothing.Coach was started about 2 weeks ago with no problem,thanks in advance.Coach is next to the shop and it's warm for awhile can trouble shoot.

Re: Another starting problem

Reply #1 – February 19, 2024, 03:49:32 pm

That is one of two identical ignition relays. They are activated by a signal from the ignition switch. It is possible you have a intermittent wiring connection or loose wire in the activation circuit, or a bad ignition switch.

On the schematic linked below, at the top left of center you will see the 2 ignition relays. To the left of them is the main HOT (engine battery) power distribution post, and to the left of that is the ignition switch. Power departs the IGN terminal in the ignition switch via the wire 103 WH and goes into the wiring harness. It comes out of the harness via wire 103A WH and goes to the activation terminals (86) on the two ignition relays.

I would suggest checking the main HOT power distribution post to be sure you have good (engine battery) voltage there.

Then check the wires on the 103 WH circuit from the ignition switch to the ignition relays for any intermittent loose connections.

If that stuff checks good, then you may need a new ignition switch. Check by jumping power directly from HOT power distribution post to the activation terminal (86) on each ignition solenoid. If the solenoids activate properly, then the ignition switch is suspect.

https://www.foreforums.com/index.php?media/file/b-2179-e31-12v-wire-u320.3300/

Re: Another starting problem

Reply #2 – February 19, 2024, 04:48:53 pm

Will do that and go from there.

Re: Another starting problem

Reply #3 – February 19, 2024, 06:24:43 pm

Quote from: John44 – February 19, 2024, 03:06:36 pm

turn the key to the on position and the start relay energies for about 5 seconds the shuts off,after a few more seconds it comes back and repeats the process,

With this frequency it may be caused by the auto resetting breaker that controls ignition. Check that breaker to see if it is bad and the wiring to same breaker has a bad spot. You may need to unplug the ignition switch plug and check the ignition switch for a short.

Mike

Re: Another starting problem

Reply #4 – February 19, 2024, 07:04:11 pm

Quote from: Pamela & Mike – February 19, 2024, 06:24:43 pm

With this frequency it may be caused by the auto resetting breaker that controls ignition. Check that breaker to see if it is bad and the wiring to same breaker has a bad spot. You may need to unplug the ignition switch plug and check the ignition switch for a short.

Mike

Or could be the coil is going bad and drawing to much current.

Re: Another starting problem

Reply #5 – February 19, 2024, 08:57:18 pm

These diagrams likely are how current flows when you turn the ignition key.

You can work backward to get the engine cranking without the ignition key.

The sequence can be VERY helpful when diagnosing a failure to crank problem.

Re: Another starting problem

Reply #6 – February 20, 2024, 01:44:40 pm

Still trying to figure out which parts are which,ordered a new ig switch from Napa,Barry read your post about replacing your switch
got the chrome piece loose but will not come all the way off,is there a detent somewhere to get off completly?

Re: Another starting problem

Reply #7 – February 21, 2024, 03:03:27 pm

Quote from: John44 – February 20, 2024, 01:44:40 pm

Still trying to figure out which parts are which,ordered a new ig switch from Napa,Barry read your post about replacing your switch
got the chrome piece loose but will not come all the way off,is there a detent somewhere to get off completly?

If there is a round hole in the chrome piece push a paperclip into the hole to release.

Re: Another starting problem

Reply #8 – February 22, 2024, 11:12:43 am

UPDATE: Installed new Ignition switch,same problem with new switch,checked the components on the metal plate that is in the back near the six pack(some are under the bed near the fuse panel),swapped out the 2 small relays,both good,of the 2 cole
hersee solenoids,the one with the smaller wires is the boost the one with the larger wires is the start solenoid(correct me if
wrong),the start solenoid has battery woltage but when I jump from battery voltage to iniciate the solenoid it makes the clicking sound and no voltage to the starter,(yes I did tap on it).Today will be checking voltage from switch to that solenoid,have a new
solenoid coming today(cole hersee 24213,still not sure how this would be causing the start relay in the front panel to cycle,any
ideas appreciated as always.

Re: Another starting problem

Reply #9 – February 22, 2024, 12:01:27 pm

Does the engine have an air manifold heater?

Re: Another starting problem

Reply #10 – February 22, 2024, 12:08:34 pm

Quote from: John44 – February 22, 2024, 11:12:43 am

...of the 2 cole hersee solenoids, the one with the smaller wires is the boost the one with the larger wires is the start solenoid (correct me if wrong)...

I think you might have the solenoid IDs reversed.

The BOOST solenoid will have large battery cables on both of the big posts. Both of these cables should be hot all the time. When the solenoid is OFF (open), one large post will read chassis battery bank voltage, and the other will read coach battery bank voltage. When the solenoid is ON (closed) the voltage should equalize and read the same on both large posts.

The AUX START solenoid should have smaller gauge wires on the large posts. When the solenoid is OFF (open) there should be voltage on only one of the large posts. When the solenoid is ON (closed) there should be voltage on both large posts, and the starter motor should try to crank the engine.

Re: Another starting problem

Reply #11 – February 22, 2024, 12:30:11 pm

Yes to Craneman,will unplug and see what happens.

Re: Another starting problem

Reply #12 – February 22, 2024, 01:56:56 pm

Checked the aux. start solenoid,no voltage to either big terminals,will try and figure that out,also on the boost solenoid voltage
only on one big terminal,will figure out if house or start batteries.

Re: Another starting problem

Reply #13 – February 22, 2024, 03:04:33 pm

Quote from: John44 – February 22, 2024, 01:56:56 pm

Checked the aux. start solenoid,no voltage to either big terminals,will try and figure that out,also on the boost solenoid voltage
only on one big terminal,will figure out if house or start batteries.

The aux start solenoid would usually receive the voltage on the large always HOT post from the chassis (start) battery bank.

Since the aux start solenoid is missing the voltage from the chassis batteries, I would guess this is also the voltage that is missing from the boost solenoid.

On our '93 model the original factory wired path of start battery voltage went from the chassis batteries to a large post on the boost solenoid, then to the isolator start battery post, then to the aux start solenoid, then it passed through the aux start solenoid and on to the starter solenoid (mounted on the starter). The newer model coaches might be different, IDK.

See generic 12V wiring schematic linked below:

https://www.foreforums.com/index.php?media/file/b-2126-automotive-wiring-diagram.4746/

Re: Another starting problem

Reply #14 – February 22, 2024, 04:18:08 pm

Have that drawing in my books,went over the cables on the house batteries,they check out ok,B12 AND B39 wires check out ok,have 12 volt to 12volt circuits,will check the B11,and go from there,looks like that sould be a straight path from battery to boost solenoid.

Re: Another starting problem

Reply #15 – February 23, 2024, 09:46:38 am

Going to go thru Barrys checklist today,will also check intake heater and fuel solenoid,may be dealing with a short somewhere.
Barry,on the end of the second page,not sure what/where the inverter panel is?

Re: Another starting problem

Reply #16 – February 23, 2024, 05:13:07 pm

Craneman,isolated preheat,no change,cleaned all grounds on engine and frame,think I'll try and isolate every resettable fuse on the front panel area one by one and see what that does.Still can't figure out why the ignition relay acts like a resetable fuse.

Re: Another starting problem

Reply #17 – February 23, 2024, 09:42:29 pm

Pull out the ignition relay and see if something still is tripping. If not it is downstream of the ignition relay.

Re: Another starting problem

Reply #18 – February 23, 2024, 11:25:22 pm

John, earlier you mentioned the start batteries were fully charged. I'm curious if they really are fully charged and able to provide good starting voltage.

Try turning on the headlights with the ignition switch off. Do the headlights turn on with normal brightness?

Then turn the ignition switch to the "on" position. Do the headlights stay bright or do they get noticably much dimmer when the relay cycles?

Then try to crank the engine, do the headlights go way down to nothing or stay bright?

Re: Another starting problem

Reply #19 – February 24, 2024, 03:02:42 am

Will do but when you turn the key to the first position everything is ok for about 5 seconds,then the lower right bosch ignition
solenoid cycles on and off,if you go to the start position,nothing.going to trace the starting voltage in the morning.

Re: Another starting problem

Reply #20 – February 24, 2024, 08:52:52 am

Quote from: John44 – February 24, 2024, 03:02:42 am

...when you turn the key to the first position everything is ok for about 5 seconds, then the lower right bosch ignition solenoid cycles on and off...

Quote from: Pamela & Mike – February 19, 2024, 06:24:43 pm

With this (on and off) frequency it may be caused by the auto resetting breaker that controls ignition. Check that breaker to see if it is bad and if the wiring to same breaker has a bad spot.

In Reply #3 Mike suggested checking the auto resetting circuit breaker that controls ignition. Did you ever do that?

In the 12V wiring schematic for your coach, you are looking for the circuit breaker marked IGNITION SWITCH 15. This circuit breaker feeds wire 91 WH which sends power to the ignition switch terminal marked BAT. As Mike suggested, if this circuit breaker is weak it could repeatedly open and close, giving the intermittent power symptom you describe.

Schematic below (for U320) shows the circuit breaker. It may be in a different position on your circuit breaker panel.

Re: Another starting problem

Reply #21 – February 24, 2024, 09:59:49 am

Will do that next Chuck and give update,getting some extra breakers coming just in case,thanks again.

Re: Another starting problem

Reply #22 – February 24, 2024, 10:28:01 am

Coach wont start trouble shooting (Battery)

Low Capacity batteries and resistance in cables and grounds are so easy to over look. You use your volt meter and see power, but it needs to remain under load.

Re: Another starting problem

Reply #23 – February 24, 2024, 10:48:58 am

I'm thinking bad starter....have you tried jumping the solenoid...IMHO

Re: Another starting problem

Reply #24 – February 24, 2024, 12:57:06 pm

Chuck,got some progress,did that procedure ,replaced with new breaker,same thing happens when you turn key the one turn
to the right but when you go start position for the few seconds before the solenoid cycles the start solenoid near the isolator
clicks,this was not happening before.will trace from there.
Hans,to your question,not yet.Took all the ground wires at the bottom of the front panel area that are on the ground lug and cleaned and put back.

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