Hello, I have A 2021 cat259d3 S/N: CW903533 The problem I’m having is my machine doesn’t want to start when it’s cold out. The glow plug light comes on for 10-20 seconds then clicks off. Try to start the machine and it will crank and crank then finally it will start. Cranking for 10 second or so… it will do this regardless if I cycle The key once or 5 times. I’ve replaced the battery, it’s brand new. And thoughts? Thank you!
From what the other guy found with his blowing glow plug fues, as a start try measuring the resistance of all four glow plugs and check if they are more or less equal. You have the electrical schematic. Try checking the function of the glow plug relay. Is it sending current to the glow plugs.? Just because the light on the panel comes on doesn't necessarily mean that there is any amps arriving at the plugs themselves.
Ok will do. I will try this tonight. Thank you
Correction… the glow plug light comes on for 5-10 seconds.
So I’ve found the fuse located by the fuel pump on the bus bar is blown. (One of the 2 fuses is blown) I check For resistance on all four of the glow plugs and they are all 2.1 ohms. I found The relay that controls the glow plugs by ohming out the wires. Found my main power from the bus bar with the blown fuse to the relay. Then found the wire that goes from the relay to the glow plug bus bar. I tested The relay is it tests good. I will Put it back together once I get A new 50A fuse. The attached picture is where the fuse was blown.
I was Slowly putting the machine back together. Meaning- I put The new fuse in, with the relay unplugged… turned the key on and then checking for continuity across the fuse. It was good. (Fuse didn’t pop) then, I plugged the relay in and had the wire disconnected from bus bar that goes to all 4 glow plugs. I turned on the key, checked for continuity across the fuse. It was good. (Fuse didn’t pop) Lastly, I connected the wire to the bus bar the connects to all of the glow plugs everything is put back to normal, I turn the key on and check for continuity across the fuse. It was no good. (Fuse was blown)
Circuit problems could be from: 1. Your 50 amp fuse may be too small for your glow plug circuit I only mention this because on my 2006 242B, I have tested my glow plugs and each glow plug individually draws 17 to 19 amps. Combined, the 4 glow plugs draw 69 to 73 amps. I had a look at my wiring diagram and it shows a maximum rating of 81.6 amps for the glow plug circuit. I realize you have a different machine, but 50 amps seems like a pretty small fuse for powering the glow plugs. Perhaps check your wiring diagram for the specs on your glow plug circuit. I was not able to find any fuse information in either my Operations and Maintenance Manual or in my Parts Manual. 2. You are shorting out in the wiring from the cold start relay to the glow plugs This is not likely a problem, but is easy to check out. Disconnect the glow plugs and activate the glow plug circuit to make sure that there is not a short between the relay and the glow plugs. You will want to start out with a pocket full of correctly sized fuses. 3. You are shorting out in one of the glow plugs. I would suggest hooking up single jumper wire from the cold start relay wire. Connect to each glow plug individually and initiate your glow plug testing. Test your glow plugs one by one to see if one of them is faulty and causing the fuse to blow. If you have a clamp on DC amp meter, it will provide an additional piece of information to confirm that each glow plug is functioning correctly.
Ok sounds good. I actually bought an 80A fuse for a spare because they didn’t have any more 50A. I will Dig back into the machine tomorrow! Thank you!!!
I just Looked and it calls for a 50A fuse
What is the glow plug rating on the wiring diagram (wire 384-RL3 BU-12)?
Honestly I’m not sure. I just Looked but I cant Find anything
Can you break the glow plug circuit down into smaller lengths by disconnecting.? You can then test each section for a short to ground starting from the fused relay and working towards the glow plugs.
As far as I know, I broke The glow plug circuit down as much as I could. Starting from the fused bus bar. I could Be wrong though
On a closer inspection of your photo I see lots of corrosion, green crusties, and possibly also humidity on all three of the fused relays. I would say all three need to be removed & disassembled, all the terminals cleaned, dried out, and everything made spick & span, then reassemble everything, install a new fuse, and see how you go.
I agree! Thanks
FYI, I cannot find any data regarding what the glow plug resistance is supposed to be. Hopefully the other poster will reply to you with the results of his tests for good vs bad.
I’m having the same problem. I cannot Find anything on them. I’m going to call my local cat today to see if they have them in stock. I also thought about putting a jumper in the relay position, then wire in the hot going out of the relay spot. Land that wire on the bus bar to the glow plugs. Turn the key on and see if the fuse blows. If it pops, I would Think my problem is in the or a glow plugs everything. If it doesn’t pop and the plugs work, I’ve got a bad wire from the relay to the glow plug bus bar.
Drays, 1. Start with a pocket full of fuses. 2. Connect a jumper wire to the wire that leaves the cold start relay. 3. Connect the jumper wire to one individual glow plug. 4. If you have a clamp on DC amp meter, clamp that over the jumper wire to measure the amp draw on the glow plug. 5. Activate the glow plug circuit on the individual glow plug being tested. 6. Record the amp draw for the glow plug being tested. If you don't have a clamp on meter, proceed to Step 7. 7. Check to see if the 50 amp fuse is still functional or failed. 8. Repeat for the each of the other 3 glow plugs individually. This likely is the best way to proceed. As the Brits say, "Suck it and see". Translation: To try something in order to find out if it is good, effective, etc. We don't know if it will work. We'll have to just suck it and see . Nige - Not sure if this a correct usage of "Suck it and see". Perhaps you can advise. The glow plugs resistances on my 2006 242B were 0.4 ohms each. And these glow plugs function fine. Note that not all engine models may have the same glow plug resistance as mine. P.S. - As Nige suggested, clean up the fuse electrical connection first before performing the above test.
With a new fuse in place, without jumpering the relay, if you disconnect the glow plug bus bar and activate the glow plug circuit, you are effectively testing the entire circuit up to the glow plugs. If the fuse blows when your do this test, the fault to ground is upstream of the glow plugs. If the fuse does not blow, then the fault to ground is most likely, almost certainly, pretty much surely in one of the glow plugs.
Sounds good to me. It is going at the problem logically, and like the challenge of eating an elephant, you have to chop it up into bite-size pieces first. When you have done all the cleaning of the main power relays, fuse holders, etc, I would suggest that you locate the 2-pin connector marked CONN 34 on the schematic (Page 11, Grid H-11), then physically on the machine (there is an illustration on Page 19), and unplug it. It is in the circuit between the glow plug relay and the plugs themselves. If the fuse does not blow when you "energize" the glow plugs with CONN 34 unplugged then it would appear that something downstream of that connector must be the root cause of the problem. However if it does continue to blow then you have to be looking between the main power relay (the one with the fuse in it) and the glow plug relay. Based on the condition of the connections at the power relays it might pay you to inspect CONN 34 closely for signs of corrosion, humidity, and/or crusties.
Yes I’ve done this. Now I’m going to test the individual plugs.
I have Looked for conn 34 and I’m not sure where it’s at on my machine. Nor do I know What it is exactly. I’ll keep trying
Can you find it on the schematic at the stated location - Page 11 Grid H-11.? If you can then click on the “CONN 34” hyperlink underneath the drawing of the connector. That will take you directly to the illustration on page 19 showing the physical location of the connector.
I found the conn 34. It’s a grey plug with a blue and white wire. It looked fine. I have Attached some pictures. See below!! !!!!!!!!!! SOLVED!!!!!!!!!!!!! Step 1- turn off the key and turn off the battery kill switch! Step 2- buy a in line fuse. I bought One that went from 5a to 30A fuses. I used 30A fuses. Take this a place it in the place of the 50A fuses on the bus bar behind the fuel pump. Step 3- build a male spade jumper. (2 male spades). Remove the cold start relay. Place this jumper in the incoming hot wire slot (red wire) and the outgoing glow plug wire slot (blue wire). Step 4- remove the bus bar to all of the glow plugs. Step 5- cut the zip tie to the wire that connects to the glow plug bus bar. Cutting this zip tie will give you enough reach to do step five… Step 6- take the glow plug bus bar wire and hook it onto the first glow plug. Make sure while hooking it to the glow plugs you do not accidentally ground it to the motor. Step 7- turn on the battery kill switch. ?? Doing this is sending 12v to that single plug. Making this a really simple way of testing each plug… Results————— if the 30A fuse does not pop, the glow plug is good. If it pops the glow plug is bad! Step 8- turn off the battery kill switch Step 9- repeat step 6, step 7 and step 8 on the next 3 plugs. After doing all of this and finding the bad glow plug or plugs.. change it and put everything back to normal. Including the in line fuse! Picture labeled (1) is the in line fuse Picture labeled (2) is the male spade jumper Picture labeled (3) is the conn 34
An excellent write-up. Kudos. So how many bad glow plugs did you find.?
Thank you!! Thank you for all of your help! It is greatly appreciated!!! I had One bad plug. The second plug. I tested it 3 times! Haha! I wanted To be sure. The in line fuse came in very handy! Easy to change those fuses rather than the bolt down fuse! Also the bolt down fuses are much more expensive. About $4.50 each. I hope This will help someone in the future! This is a wonderful forum!!
Thank you very much for all of your help!
You're welcome. I am guessing that by now you know a lot more about your machine electrical system than you did when you started.?
Haha! Yes indeed! That the good part about working on something yourself! You learn a lot about the machine! Onto the next problem!! (Backup camera) haha!