Why does my sperry DM6450 multimeter read "connect terminal" even when both are connected?

Actually that's normal operation.

Meters such as this have a range of resistance that they are capable of measuring. When you first turn them on, the resistance across the leads (or in your case, across the lead connections) is basically infinitely. This resistance is beyond the meter's ability to measure and displays that tbe reading is out-of-range, a.k.a. overload.

When you plug the leads in and touch them together. the reading should display correctly, such as 0 ohms (or possibly a small value due to lead resistance.)

Hello Anthony, I sent you a link so you can find out the manual of the tester Sperry DM-210a and another where you get an explanation of the operation
I hope you can solve your concern
Greetings Franco Dosil

Hola Anthony, te envio un link para que puedas descrgar el manual del tester Sperry DM-210a y otro donde te dan una explicacion del funcionamiento
Espero que puedas resolver tu inquietud
Saludos Franco Dosil

https://www.hunker.com/13414165/how-to-use-a-sperry-dm-210a-meter

https://greenlee-cdn.ebizcdn.com/media/52058078REV01.pdf

https://www.hunker.com/13407450/instructions-for-a-sperry-dm-210a

Refer to instructions that came with meter, it is there. If you threw away instructions here is a big hint.
https://www.manualslib.com/manual/1346232/Sperry-Instruments-Dm6450.html?page=6#manual

Set the knob to the ~600V position. With the power on/connected, place one test lead on one side of the fuse and the other test lead on the other side of the fuse. Be careful not to touch anything with your hand or you will get shocked. If you read voltage the fuse is bad. If you don't read voltage the fuse is bad.
Alternately you could DIS-connect power remove the fuse and test the fuse for OHMs, which on your meter is the last icon with the ((((.
It will beep and/or read very low ohms <5.

Here's the manual -

Sperry Instruments DSA 500 Operating Instructions

remove battery door and replace 9V battery

detailed explanation bellow
http://www.testequipmentdepot.com/sperry-instruments/pdf/dm6400.pdf

try cleaning terminals with compressed air just in case if there is some dirt inside, other than that you will need new meter

Ford Excursion, Expedition, Lincoln Navigator 2000-2005
Starter

• REMOVAL & INSTALLATION
• TESTING & TROUBLESHOOTING

Print

Removal & Installation

1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
   
   Negative battery cable
   
2. Raise and safely support the vehicle.
3. Remove or disconnect the following:
   NOTE To disconnect the hard-shell connector from the solenoid S terminal, grasp the plastic shell and pull off; do not pull on the wire. Pull straight off to prevent damage to the connector and S terminal.
   
   
   Starter terminal cover Terminal nut and separate the battery starter cable from the starter motor Solenoid S terminal connector, if equipped with a starter mounted solenoid
   
4. Remove or disconnect the following:
   
   Starter motor retaining bolts Starter motor from the vehicle
   

To install:

1. Install or connect the following:
   
   Starter motor and retaining bolts. Tighten the bolts to 15-20 ft. lbs. (20-27 Nm). Bttery starter cable and a terminal nut to the starter motor. Tighten the terminal nuts to 79 inch lbs. (9 Nm). Slenoid S terminal connector, if equipped with a starter mounted solenoid Sarter solenoid safety cap, if equipped
   
2. Lower the vehicle.
3. Remove or disconnect the following:
   
   Ngative battery cable
   
4. Start the engine several times to check starter motor operation.

1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
2. Remove or disconnect the following:
   
   Negative battery cable
   
3. Raise the front of the truck and install jackstands beneath the frame. Firmly apply the parking brake and place blocks in back of the rear wheels.
4. Remove or disconnect the following:
   
   Wiring from the starter motor terminals Starter motor retaining bolts, loosen Starter retaining bolts while supporting the starter motor Starter from the vehicle
   

To install:

1. The installation is the reverse of removal. Tighten the starter retaining bolts to 15-20 ft. lbs. (20-27 Nm)

4.6L, 5.4L & 6.8L Engines

1. Before servicing the vehicle, refer to the precautions section.
2. Disconnect the negative battery cable.
3. Raise and safely support the vehicle.
4. Remove or disconnect the following:
   NOTE To disconnect the hard-shell connector from the solenoid S terminal, grasp the plastic shell and pull off; do not pull on the wire. Pull straight off to prevent damage to the connector and S terminal.
   
   
   Starter terminal cover Terminal nut and separate the battery starter cable from the starter motor Solenoid S terminal connector, if equipped with a starter mounted solenoid
   
5. Remove or disconnect the following:
   
   Starter motor retaining bolts Starter motor from the vehicle
   

To install:

1. Install or connect the following:
   
   Starter motor and retaining bolts. Tighten the bolts to 15-20 ft. lbs. (20-27 Nm). Battery starter cable and a terminal nut to the starter motor. Tighten the terminal nuts to 79 inch lbs. (9 Nm). Solenoid S terminal connector, if equipped with a starter mounted solenoid Starter solenoid safety cap, if equipped
   
2. Lower the vehicle.
3. Connect the negative battery cable.
4. Start the engine several times to check starter motor operation.

6.0L Diesel Engine

1. Before servicing the vehicle, refer to the precautions section.
2. Disconnect the battery ground cable.
3. Remove starter solenoid protective cap.
4. Disconnect the starter motor electrical connections.
5. Remove the bolts and the starter.

To install:

1. Installation is the reverse of the removal procedure. Tighten the starter bolts to 18 ft. lbs. (25 Nm)

7.3L Engine

1. Before servicing the vehicle, refer to the precautions section.
2. Remove or disconnect the following:
   
   Negative battery cable
   
3. Raise the front of the truck and install jackstands beneath the frame. Firmly apply the parking brake and place blocks in back of the rear wheels.
4. Remove or disconnect the following:
   
   Wiring from the starter motor terminals Starter motor retaining bolts, loosen Starter retaining bolts while supporting the starter motor Starter from the vehicle
   

To install:

1. The installation is the reverse of removal. Tighten the starter retaining bolts to 15-20 ft. lbs. (20-27 Nm)

Testing & Troubleshooting

Feed Circuit Test

1. Make sure the battery is fully charged.
2. Disconnect the Inertia Fuel Shutoff (IFS) switch.
3. Connect a remote starter switch between the starter solenoid S-terminal and the battery positive (+) terminal.
4. Connect the Rotunda 73 Digital Multimeter positive lead to the battery positive (+) post. Connect negative lead to the starter solenoid M-terminal.
   
   

   Fig. Motor feed circuit-S-terminal (1), remote starter switch (2), battery (3), Rotunda 73 digital multimeter (4), B-terminal (5), M-terminal (6)
   

5. Engage the remote starter switch. Read and record the voltage. The voltage reading should be 0.5 volt or less.
6. If the voltage reading is 0.5 volt or less, go to the Motor Ground Circuit Component Test.
7. If the voltage reading is greater than 0.5 volt, indicating excessive resistance, move the Rotunda 73 Digital Multimeter negative lead to the starter solenoid B-terminal and repeat the test. If the voltage reading at the B-terminal is lower than 0.5 volt, the concern is either in the connections at the starter solenoid or in the solenoid contacts.
8. Remove the cables from solenoid B-, S- and M-terminals. Clean the cables and connections and reinstall the cables to the correct terminals. Repeat Steps 3 through 6. If the voltage drop reading is still greater than 0.5 volt when checked at the M-terminal or less than 0.5 volt when checked at the B-terminal, the concern is in the solenoid contacts. Install a new starter motor.
9. If the voltage reading taken at the solenoid B-terminal is still greater than 0.5 volt after cleaning the cables and connections at the solenoid, the concern is either in the positive (+) battery cable connection or in the positive battery cable itself.
10. By moving the Rotunda 73 Digital Multimeter negative lead toward the battery and checking each mechanical connection point, the excessive voltage drop can be located. When the high reading disappears, the last mechanical point that was checked is the concern. Repair or install a new connection as required.

Ground Circuit Test
A slow cranking condition can be caused by resistance in the ground or return portion of the cranking circuit. Check the voltage drop in the ground circuit as follows:

1. Disconnect the inertia fuel shutoff switch.
2. Connect a remote starter switch between the starter solenoid S-terminal and the battery positive (+) terminal.
3. Connect the Rotunda 73 Digital Multimeter positive lead to the starter motor housing (the connection must be clean and free of rust or grease). Connect the negative lead to the negative (-) battery terminal.
   
   

   Fig. Motor ground circuit-Rotunda 73 digital multimeter (1), battery (2), S-terminal (3), M-terminal (4), B-terminal (5), remote starter switch (6)
   

4. Engage the remote starter switch and crank the engine. Read and record the voltage reading. The reading should be 0.2 volt or less.
5. If the voltage drop is more than 0.2 volt, clean the negative cable connections at the battery and body connections, and retest.
6. If the voltage drop is greater than 0.2 volt, determine which way the current is flowing in the cable.
7. Connect the Rotunda 73 Digital Multimeter positive lead to the end of the cable nearest battery positive.
8. Connect the multimeter negative lead to the terminal at the other end of the cable.
9. Crank the engine and observe the voltage reading. The voltage reading should be 0.2 volt or lower. If the voltage drop is too high, clean the terminal ends. Retest, and if still high, install a new cable. If the voltage reading is less than 0.2 volt and the engine still cranks slowly, install a new starter motor.

Voltage Drop Test

WARNING When servicing the starter motor or performing other underhood work in the vicinity of the starter motor, be aware that the heavy gauge battery input lead at the starter solenoid is "electrically hot" at all times.

WARNING A protective cap or boot is provided over the battery input terminal on all vehicle lines and must be installed after servicing. Be sure to disconnect the battery ground cable before servicing the starter motor.
Always make the Rotunda 73 Digital Multimeter connections at the component terminal rather than at the wiring end connector. Making a connection at the wiring end connector could result in false readings because the meter will not pick up a high resistance between the wiring connector and the component.

If you have some electrical know how you can try to trace the draw yourself. You will need a multimeter capable of measuring amps.

First dis-connect the negative terminal, and make sure your dome light and everything else is turned off.

Next connect the multimeter in between the terminal and battery connection basically completing the circuit, and make sure the meter is set to amperage.

You should get a reading somewhere around 14-25 milliamps depending on how old or new the vehicle is. If you have a reading of say 200 milliamps then you have a draw somewhere.

Now once you get a clear level reading start by removing individual fuses and seeing if the reading goes down. Once you find the fuse that drops the reading down to an acceptable level you found the circuit that has the problem.

At this point you would have to trace individual parts of the circuit to find the specific draw which requires a fair bit of know how, and should be done by someone with this knowledge.

I assume a "DM-350a" is some kind of a digital multimeter. I Googled and found it might be a "A.W. Sperry DM350A 5 Function 17 Range Digital Multimeter" and looking at the ranges available on that meter, you can't really thest the battery "under load" the only reasonable way to test small batteries. the DC current only goes up to 200 milli amperes. A "C" or "D" size flashlight battery puts out 1 to 4 amps depending on conditions. That's 5 to 20 times the current readable by that meter. The volts on one of those batteries is probably 1.6 volts to 1.3 volts etc. If you live in the United States, I'd say go to Radio Shack and spend $5 to $15 and buy a battery tester like "Enercell Analog 9-Range Battery Checker, $14.99, Model 22-156, catalog # 22-156"
Then you and anyone in your family can read the instructions and test 8 or 9 different type batteries. Battery types: 1.5V button-cells, "AAA"/"N"/"AA"/"C"/"D", 6V, 9V, 12V, 15V and 22.5V..
This is not supposed to be an advertizement, and I have no interest in RadioShack,... but it's supposed to be instructional.

Small price, Good instruction to anyone who can read, and if anyone forgets, they can re-read. Testing a lot of batteries in a sitting goes very fast with these.

Differently, with the sperry, or any voltmeter, you'd have to select a resistor small enough to draw the current, and large enough not to overheat or burn, connect it and measure the loaded voltage drop, compare the voltage and current of the loaded battery, and compare it to that of a new battery, and a battery you might consider too weak for your application.. Voltage equals amps times resistance, and power equals amps squared times resistance... Really, buy a battery tester.
Regards --- GooseBay_Camper

The most obvious solution to your problem is that you may have the meter simply connected backwards. To make life easy, Groovetubes sells a thing called a bias probe that makes biasing tube amps a breeze.