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SPM-HEP-4749 is the 28 volt, 45 amp alternator with a cooling fan, aluminium housings, a single mounting foot and a top adjusting lug. It is used on Cummins 4BT3.9 engines. This aftermarket version has the same mounting and electrical connector as the original, so it plugs in and bolts on where the old one came off.
It replaces Cummins 4938300 and Cummins 37V66-01010.
Sold as one unit. Check the number on your old part, or in the parts manual for your machine, before ordering.
| Part Type | Alternator |
| Replaces | Cummins 4938300 |
| Engine | Cummins 4BT3.9, 4BTA, 6BT |
| Output | 28 V, 45 A |
| Cross references | 37V66-01010 |
| Fits | Cummins 4BT3.9, 4BTA and 6BT diesel engines |
| Condition | New, aftermarket |
| Stat. HS-Code | 851150 |
| Country of Manufacture | China |
Cummins machines
Check the part number on your old unit before ordering.
| Cummins Part No.(SPM Part No.) | Fits |
|---|---|
| 4938300(SPM-HEP-4749) | Cummins 4BT3.9, 4BTA and 6BT diesel engines |
| 37V66-01010(SPM-HEP-4749) | Cummins 4BT3.9, 4BTA and 6BT diesel engines |
Battery not charging
A charge warning light or flat batteries every morning point to the alternator once the belt and wiring check out.
Noise
A worn bearing whines or grinds.
Low voltage at idle
Weak output shows as dim lights and slow electrics at idle.
Fit with a new belt
Change the belt and check the tensioner when fitting the alternator.
We check what other aftermarket sellers charge for this same part. Their prices on the date we checked:
| Seller | Price | Checked |
|---|---|---|
| Buy Machinery Parts | USD 216.60 | 4 Nov 2026 |
| eBay, aftermarket seller | USD 241.50 | 31 Oct 2026 |
| SINOCMP | USD 269.00 | 31 Oct 2026 |
| MyMROmarts | USD 332.99 | 4 Nov 2026 |
| Spare Part Mart | USD 176.00 | Today |
Our price of USD 176.00 is 19% to 47% less than these sellers.
Found this part cheaper somewhere else? Send us the listing and we will beat it by 5% under our Price Beat Guarantee. Every order is also covered by our 30 day money back guarantee.
Yes, it was made for the Cummins 4BT3.9, and 2 more listed under compatible equipment. Check the old alternator is marked 4938300 or one of the cross references, because makers change parts between serial ranges.
On the Cummins 4BT3.9, typically 5,000 to 10,000 hours, depending on how often the machine is started and how well the batteries are kept.
A charge warning, low battery voltage with the engine running, flickering lights or bearing noise.
Battery voltage under load, the earth strap and the main cable. A weak supply makes a good alternator look faulty and will burn out the new one.
Check the old unit before you send it away. Pulleys and fans are often fitted to suit the machine and have to be moved across.
No. It is an aftermarket alternator made to replace the Cummins 4938300. It is not made by the original manufacturer; the number only shows what it replaces.
Live rates for the quantity selected, delivered to your door. Confirmed at checkout.
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