transmission light

[farmboy 12]

Have a bobcat 742b with a transmiddion warning light that won't go off. Have replaced hydralic filter and oil level is fine. Everything seems to work fine but the light worries me. Any suggestions? Thanks.

 

[OldMachinist]

Likely the sending unit is bad or has broken electrial connection. To verify remove the sender and install a pressure gauge in its place. Charge pressure should be 140-170 psi for serial #14999 down and 95-115 psi for serial #15001 and up.

 

[frogfarmer]

Likely the sending unit is bad or has broken electrial connection. To verify remove the sender and install a pressure gauge in its place. Charge pressure should be 140-170 psi for serial #14999 down and 95-115 psi for serial #15001 and up.

Three sensors can illuminate your trans light. The charge pressure sensor; the trans temp sensor (fluid temp); and the filter condition sensor. Any one of these can give you a light. If you have low charge presssure you can destroy the hydro pumps. If you have high fluid temp you may have a restriction or failing part. The filter condition sensor measures pressure in the filter manifold, when it reaches a set pressure the light comes on; normally the filter will have very low pressure. On a machine of that age a wiring problem can cause a light. If you unplug a sensor and the light goes out you likely have found the problem area. I would verify you have charge pressure with a guage before damage can be done.

 

[farmboy 12]

Three sensors can illuminate your trans light. The charge pressure sensor; the trans temp sensor (fluid temp); and the filter condition sensor. Any one of these can give you a light. If you have low charge presssure you can destroy the hydro pumps. If you have high fluid temp you may have a restriction or failing part. The filter condition sensor measures pressure in the filter manifold, when it reaches a set pressure the light comes on; normally the filter will have very low pressure. On a machine of that age a wiring problem can cause a light. If you unplug a sensor and the light goes out you likely have found the problem area. I would verify you have charge pressure with a guage before damage can be done.

The transmission light goes out for just a second when I raise the boom and then comes back on. Could this be caused by a bad filter sensor? Also, where is charge pressure sensor located? Looks like a fun job to get to if it is where I think it is.

 

[OldMachinist]

The transmission light goes out for just a second when I raise the boom and then comes back on. Could this be caused by a bad filter sensor? Also, where is charge pressure sensor located? Looks like a fun job to get to if it is where I think it is.

On the early machines its in the side of the port block and on the later in a elbow on top hydrostatic pumps. Does the light come on as soon as you start it or does it take a while?

 

[farmboy 12]

On the early machines its in the side of the port block and on the later in a elbow on top hydrostatic pumps. Does the light come on as soon as you start it or does it take a while?

the light comes on as soon as I start it and only goes off or flickers when I raise the boom.

 

[Tazza]

the light comes on as soon as I start it and only goes off or flickers when I raise the boom.

Sounds like a possible charge pressure issue. When you lower the arms you will generate more oil flow hense the light going out. It sounds like a filter restriction or a problem with your charge felief valve.
Does it have lots of power still? or does it struggle to turn and push?

 

[mrfixitpaul]

Sounds like a possible charge pressure issue. When you lower the arms you will generate more oil flow hense the light going out. It sounds like a filter restriction or a problem with your charge felief valve.
Does it have lots of power still? or does it struggle to turn and push?

Could also be a wire came off at one of the sensors and is grounding out.

 

[farmboy 12]

Sounds like a possible charge pressure issue. When you lower the arms you will generate more oil flow hense the light going out. It sounds like a filter restriction or a problem with your charge felief valve.
Does it have lots of power still? or does it struggle to turn and push?

the light only goes out for a second when I raise the boom. It still has lots of power and shows no change at all in the way it turns or pushes.