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GaryB_from C · 02-19-2016, 07:17 PM

After driving over a road with a lot of potholes I developed a starting problem.
I can't start the RV unless I hold down the "emergency start" switch while using the ignition/starter switch. Most of the time the ignition switch appears to be dead but occasionally if I turn it to the start position I can hear a single click but the starter does not engage. Once the RV is started everything works like normal.

The RV is a 2005 Tiffin Allegro on a Ford F53 chassis.

My suspicion is that either something was jarred loose or some solenoid is bad.

I've checked all the fuzes I can find. I even swapped some identical solenoids.

I don't think it is the same issue I read about here where the starter relay had gone weak because once the system is energized with the house power everything works like normal.

twinboat · 02-19-2016, 07:43 PM

Start battery dirty connections will give you your problem.

Take them off, clean them and put them on tight.

dpinvidic · 02-19-2016, 07:44 PM

By holding down the "Emergency Start" all you are doing is jump starting your rig...just like in a car, but without the jumper cables.

So what this means is that your ignition switch and starter is fine.
The problem lies in your chassis batteries, or the cables that connect them.

Trace out all the big cables and make sure the connections are clean and solid.

Have you measured the voltage of the chassis batteries??

Regards,

Dan

jacwjames · 02-19-2016, 08:23 PM

I had about the same symptoms, sometimes when I would try to start nothing. Turn the key off and try again and it would start.

It ended up being my chassis battery disconnect. It basically failed, I removed and tied the two leads together and it started. I replaced the disconnect and it fixed the problem.

I actually bought 2 to keep a spare since I have the same thing for the house batteries.

FWIW I seldom use the disconnects so it's not like it wore out, it just failed, no other signs then just the starting problem. I tried to take the failed one apart but it is a sealed unit but I could never get any continuity across the posts so the contacts failed.

GaryB_from C · 02-19-2016, 09:04 PM

Quote:

Originally Posted by jacwjames

It ended up being my chassis battery disconnect.

Excuse my ignorance but what is a "chassis battery disconnect"? What does it look like and where is it most likely located?

My battery terminals are clean and the voltage on the house and chassis batteries are all above 12.6 volts.

twinboat · 02-20-2016, 03:56 AM

A test you can try is to measure the start battery voltage while holding the key to start.

Measure at the battery posts, then the cables, then the ground wire where it bolts to the frame or engine.

If it drops to zero anywhere on the cable, the connection is bad.

If it drops to zero right on the battery post, not the wires on the post, the battery is bad.

If you are looking at the battery cables and claiming they are clean, the still can be dirty. You can not see a dirty connection, the corrosion is in between the pieces.

You may not have a chassis battery disconnect on your Ford chassis. If you do, there will be a switch labled for it.

Follow the chassis battery cable from the battery. It will go to a disconnect switch and then the starter. If it goes right to the starter, no disconnect.

Another quick test is to touch the battery connections with your hand and feel for a warmer one, after holding the key to start for 30 seconds. A warmer one means bad connection.

Good luck with your tests.

GaryB_from C · 02-20-2016, 12:19 PM

Thanks everyone for the suggestions. The problem and fix was simple as the problem was a bad connection between the battery clamp and the cable. Once I took it all apart and cleaned everything, I was back in business.

**CLIFFTALL** · 02-20-2016, 12:32 PM

Thanks for the update. Glad you got it fixed.

hawkeye1995 · 02-20-2016, 07:40 PM

Same problem I had on a P32 chassis. The battery connection was loose. Glad you found it.

TeJay · 02-21-2016, 09:48 AM

You got good information and solved your problem. That's always great.

This is just a bit more information which may make your next diagnosis a bit easier. Electrical issues are usually more directly related to how much amperage/current a device is using and not as much related to voltage.

When any electrical load/device is working the amount of current it needs is directly related to the amount of work we are asking it to do. A dash light requires less than a head light. A heater blower requires more current flow than an overhead light.

The starter motor is the largest load of just about anything on any vehicle. Most starter motors require about 150 amps of current. That amperage is needed to overcome the engines friction and cylinder head compression.

If you hear a clicking noise when trying to crank an engine that is the solenoid closing. You can measure your battery and it may read 12 volts but that information is almost useless in diagnosing your no crank issue.

If a circuit requires a lot of current then the wires carrying the current need to be bigger (heavier gauge) and all connections need to be good. You found that out by solving your problem. The usual analogy used is a water pipe. Heavy current needs a pig diameter pipe to allow sufficient current to flow. Loose connections present a resistance to the flow of current just like a kinked hose. You need volume to make the starter crank.

Voltage is the pressure needed to move the current (electrons) but based on the load (current needed) the flow requires a large diameter wire not being hindered by being loose or corroded (kinked).

NEVER, NEVER forget that the need for tight clean connections is just a true for the negative as it is for the positive. Many an owner and technician has been bitten by not checking the ground side of a circuit. Just last month I fixed a set of stairs that didn't always go up and down. All I did was loosen and tighten a grounding lug.

TeJay

**TonyDi** · 02-21-2016, 02:46 PM

Thanks for the update. Glad you got he issue resolved. BTW did you find your chassis battery disconnect?

twinboat · 02-21-2016, 03:07 PM

Any mechanic will head right for the battery terminals if the symtoms are, "Had dash gauges or lights. I turned the key to start and they went out".

Some times the lights come back and sometimes the clamp melts a bit and reconnect enough to start.

I have seen where some 4D battery posts melt right out of the clamp on some 24 volt start machines.