starter cylenoid

Solenoid?
Take it off, connect it to a known good battery. Does it click?
Now days starter solenoid is part of the starter. So take the starter out take it to a rebuilder and have it tested.

Might be bad battery or battery cable connection.

If it clicks the coil should be good.
You should be able to read same voltage on the large contacts when a helper energizes it.
You could use a single jumper cable between the two large posts. This should turn engine over. However it could have a Bendix type drive on the starter.

Clean your battery terminals and if necessary, have your battery tested. The engine battery, not house battery.

What engine do you have? Gas or DP.

I can only tell you my experience with a gasser.
Mine had 'several' solenoids! And it is a common problem for one to ho out.

Back in the day there was only one solenoid and it was 'not' part of the starter. Now a days the solenoid on the starter is sold as one as an assembly.

That said. I had Mobil RV repair come out.
I turned key while he checked each solenoid. Saying a prayer it was not the one on the starter!

Luckily it was not the one connected to the starter. Inexpensive part and a couple of minutes to replace.

Since you are focusing on a specific solenoid then yes they are extremely easy to test.

Follow the advice of using a voltmeter while having someone turn the key.

Solenoids are just dumb switches that let a little power control a big power. The voltage on the little connection or connections is being controlled by the ignition switch. Some solenoids have just one little connection and use the housing of the solenoid for ground via the mounting hardware.

Since your relay is "clunking", a highly technical term used by we that have diagnosed thousands of relay/solenoids then you simply need to measure the voltage on the large terminals while someone turns the key.

Before turning the key get the voltmeter set up and touching one of the large terminals. IF you can follow the large wire to the battery measure that wire/post at the solenoid before turning the key.

Write the voltage down and don't try to remember it. Trust me on this.

Now have someone turn the key. Measure again and if the voltage holds steady close to the previous measurement then move the meter to the other post while the ignition key is still turned.

The voltage on the other side should be the same. A solenoid just puts a jumper together inside the solenoid.

Solenoids become pitted and can easily fail.

Do Not go pulling and tugging on wires until you get those measurements written down. If you accidently fix a bad connection you will not be sure what it was that fixed the problem.

If the voltage on both posts is staying around the same voltage with the key being turned then you need to move further down the line which can be tricky and dangerous.

Follow the big wire to the starter. It may have another solenoid attached and the same measurement technique applies. However being that close to moving things can be dangerous so the use of alligator clips with wires can take you out of range of things.

Once you get the appropriate measurements then you can easily diagnose the problem with confidence.

Just jumping in and cleaning battery posts and grounds can solve the problem but one would not know for sure if there is an intermittent solenoid.

This is an excellent video. He does a great demonstration. Click this link.

video

I do NOT recommend taking the solenoid out to test it under your conditions. You can easily make it start working and there is danger removing the huge wires if not done safely. Testing it under working conditions is best as you will see in the second half of the video. A test light is fine but a voltmeter will tell us technicians much more while helping you.

video

How would you know if a generator works if it won’t start? In my book, “won’t start” is one mode of “doesn’t work.”

I've never had much luck chasing voltage around when you are dealing with a high amp device like a starter.
Solenoids can have very burnt or corroded contacts and still read the correct voltage but do not have the surface area left to pass 50+ amps of current.
I prefer to jumper around the solenoid with a heavy duty jumper cable to see if the starter itself is good. This is ONLY after checking the battery and all connections and cables to insure that they have the ability to provide the amps necessary to energize the starter.
When running a jumper to bypass a solenoid I prefer to hokk one jumper up to the connection on the starter, and then use another jumper cable that is connected to a battery. When everything is clear, I would then touch the two ends of the jumper cables together while I was not under the rig.

With red face and tired body, I need to share this. After much work, searching, reading, I saw the engine switch in the back of the RV. It was in OFF position and it should have been forward. Started the RV, everything works, I must have hit it when changing a bulb in my tail lights. I thought the switch should have been in the off position instead of forward. Now I know and I'm sure I will never forget. MAN am I happy RVer. Even my wife was happy after I woke her at 2:45 a.m. this morning to tell her the news.
Thanks for all of you that answered my post.