302.7d solenoid problem

[Catjoy]

Ordered part number 3860880 $744 non returnable/no warranty from CAT solenoid and before I put it on, I’m looking for some advice. What causes a solenoid to fail? I don’t want to put it on and it fail in 20 minutes because there is really another underlying problem.
“Replacement pressure relief solenoid for main control valve assembly that directs main pump oil for main functions of Cat machine” is the description…all I know is that my hydraulics quit working. It seems to go to the the blade controls and the fast/slow driving speed. Cat 302.7d. Any advice, appreciated.

 

[uffex]

Hi
The common cause of solenoid break down is that the winding circuit has a break, not so common maybe vibration & heat contribute. You can check out the windings easily with a multimeter I guess according to your photo's it is a little late for that.
Kind regards
Uffex

 

[heymccall]

Well, you definitely NOW have a bad solenoid.

As suggested above, most solenoid failures are electrical, in that the windings either break or melt together.

I'm a little slow here, so, maybe you could tell me why you focused on this part initially?

If ALL hydraulics quit, I'd think open pilot solenoid or broken pump coupling.
I'm a little rusty on Cat minis, but, IIRC, the blade is typically run off a gear pump and everything else is from the main pump(s).

 

[mikemcc]

15/01/24. Hello Catjoy. I got exactly the same problem.
Did you get it resolved?

 

[007]

There is a lot of reasons the coil will fail and it is usually heat which causes the coil to swell and expand and often breaks the coil wire some where internally causing an open circuit or short.
If the slightest spec of debris gets caught between the internal plunger and the S/S sleeve can cause the internal plug not to travel all the way up inside the coil magnetic field when energized.
This causes excess current to be drawn by the coil and over heats it.
Since it sounds that you have purchased the complete solenoid that resolves that possibility.
Under voltage when energized can cause a week magnetic field and cause the same problem.
Checking the new unit with a multi meter should resolve any issues like that.

 

[Nige]

15/01/24. Hello Catjoy. I got exactly the same problem.
Did you get it resolved?

As he hasn't been on the site for over a year, and never responded to questions from others who were trying to help (see above) my suggestion would be to start again from scratch.

Describe the problem you have on your machine and any information that might be relevant regarding how it started. Throw in a Serial Number as well and I'm sure someone will try to help you.

 

[Pgarcia2]

Looks like i have the same exact problem does anyone know if there is a compatible part or after market part?

 

[Nige]

Looks like i have the same exact problem does anyone know if there is a compatible part or after market part?

Are you SURE that solenoid is your problem or do you just THINK it is your problem based on symptoms.?
What machine do you have.? S/No.?
What symptoms do you have.?

As mentioned above by @007 neither of the other two posters enquiring about this have ever been back since their first visit, so your diagnosis is going to have to be done from scratch.

 

[Pgarcia2]

its a cat 302.7d cr am having problems with the same solenoid listed on the pictures above am testing it with direct current and doesnt seems to open..i lost power on some hydraulic cylinders looks like thats the main solenoid for the line gp control from there goes straight to swing drive..my swing power aint working eather

 

[Nige]

its a cat 302.7d cr

OK, here's the deal. There are different models of 302.7D and different characteristics within those models depending on Serial Number. That's why it's needed. With the S/N at least there is halof a chance of looking up technical information.

Have you lost ALL hydraulic functions or just some.? If it is only some then please give a list of what functions are affected.

am testing it with direct current and doesnt seems to open

Have you tested the resistance of the solenoid coil.? How many ohms did you measure.?

 

[Pgarcia2]

The solenoid its reading 6 ohms and i lost power on the swing and the bucket cylinder as well

 

[Nige]

i lost power on the swing and the bucket cylinder as well

Do you have hydraulic functions on everything else.?
From memory that would be travel, dozer blade, boom, and stick functions.

 

[Pgarcia2]

thats right everything else is working

 

[Nige]

To me 6 ohms of resistance on a solenoid coil of that type seems awfully low. I would have expected it to be in the 70-100 hom range. Problem is I can't find a specification to tell me what it should be.

 

[Pgarcia2]

Well i installed the new part and didnt fix the problem know i dont have current on plugs it might have a short somewhere will keep you posted

 

[Nige]

If you would like to post a Serial Number you're welcome to an electrical schematic to help you trace power.

 

[ThadSchug]

I think I have a similar problem to this but not 100% sure. My 302.7D keeps blowing fuse #4, which goes to the horn and the hydraulic solenoid. I actually took it in for service at a dealership 3 yrs ago for the same symptoms. They replaced the entire wire harness and charged me almost 6K. Now the same symptoms, fuse #4 popping when engaging any hydraulics. Fuse #4 is labeled horn and hydraulic solenoid, Horn has never worked or been used. Any suggestions on where I should start trying to diagnose? I can't aford another 6K trip to the shop for a non fix. Thanks!!!!

 

[Nige]

Start with a Serial Number please. That gets you an electrical schematic.
You'll need a multimeter for some of the diagnosis.

 

[ThadSchug]

Thanks for asking, the Serial Number is Cat 3027DHLJ700271. Symptoms are, machine start, but then hydraulics are enguadged the #4 10 am fuse (horn and hydraulic solenoid) blows. Sometimess hydraulics work for a min or 2 , then the fuse blows. I'm not sure where the solenoid is to even check to look it over. Thanks, much appreciated.

 

[Nige]

Check your message inbox. electrical schematic on the way,

That circuit seems to feed two solenoids, 386-0559 for the implement lockout (mounted on the hydraulic pump) and 386-0880 (munted on the main control valve) for the dozer blade. I would suggest maybe unplug the solenoid for the blade and see whether or not the fuse continues to blow.