MCI SERVICE INFORMATION

 

"Not Generating" Troubleshooting Guide

MCI coaches have been equipped with Delco alternators and external regulators for many years. When working properly, this charging system provides up to 270 amps of 24 volt power to the coach electrical system. It can be very confusing and time consuming to troubleshoot this system if it is not working properly, so a troubleshooting guide has been created to assist in following specific steps to determine the cause of the system failure.

This guide is created in the form of a series of questions that require yes and no answers, and applies to all MCI coaches equipped with Delco alternators prior to the D4000 and D4500 equipped with multiplex (MUX) electrical systems. Each answer directs you to the next step in the troubleshooting sequence. This guide can be printed out, or you can utilize it directly off of the MCI website. When using the Internet, selecting the underlined yes and no answers will automatically advance you to the next step.

STEP CONDITION ACTION RESULT GO TO
1

Engine running
Air pressure built up

Alternator is not charging and "no gen" tell tale light at the dash is on. Yes
No
Step 2
Step 26
2 Engine running Check stud #33 located in the rear electrical box for 12 volts. Yes
No
Step 9
Step 3
3 Engine running Check stud #49 located in the rear electrical box for 24 volts. Yes
No
Step 4
Step 12
4 Engine running Check stud #48 located in the rear electrical box for 6 to 11 volts (voltage depends on the condition of the batteries and output of the alternator). Yes Step 52
  Stud #48 reads battery voltage (24 volts). Yes Step 53
  Stud #48 reads 0 to 5 volts. Yes Step 5
5 Engine stopped
Master on
Remove cover on voltage regulator located in the #3 baggage compartment. Check for 24 volt power. (On old regulator part #7G-4-1, terminal marked "A1". On new regulator part #07-04-1001, terminal marked "A1, Ing.") Yes
No
Step 6
Step 49
6 Engine stopped
Master on
Check "F1" on the voltage regulator located in the #3 baggage compartment for output voltage. Yes
No
Step 17
Step 19
7 Engine stopped
Master off
Remove "F1" wire located in the #3 baggage compartment from the voltage regulator "F1" terminal, and measure the resistance of the wire to chassis ground. It should read 3 to 5 ohms of resistance. Yes
No
Step 18
Step 8
8 Engine stopped
Master off
Remove the "F1" wire located in the #3 baggage compartment from the "FLD" terminal on the alternator (tape it up and make sure that it is not touching anything). Read the resistance of the "F1" wire. It should read Infinity. Yes
No
Step 15
Step 42
9 Engine running Check for a ground on pin #7 of the discharge and blower relay located in the rear electrical box. Yes
No
Step 10
Step 43
10 Engine stopped
Master off
Check for a ground on pin #7 of the discharge and blower relay located in the rear electrical box. Yes
No
Step 11
Step 24
11   Replace the discharge and blower relay located in the rear electrical box with 12 volt relay part #7D-5-1. Continue Step 54
12   Go to the field relay located in the rear electrical box and check pins 1 & 8 for 24 volts. Yes
No
Step 13
Step 38
13   Go to the field relay located in the rear electrical box and check pins 3 & 6 for 24 volts. Yes
No
Step 14
Step 33
14   Go to stud #49 located in the rear electrical box and check for 24 volts. Yes
No
Step 4
Step 50
15 Engine stopped
Master off
Remove wire "F1" off the "FLD" terminal on the alternator. Meter the resistance of the "FLD" terminal. It should meter 3 to 5 ohms of resistance. Yes
Open
Shorted
Step 16
Step 22
Step 21
16 Engine stopped
Master off
Main disconnect on
Remove wire "R1" off the relay terminal on the alternator. Meter the voltage of relay terminal. It should be less than 1.5 volts. Yes
No
Step 11
Step 22
17 Engine running Check for 12 volts on stud #33 located in the rear electrical box. Yes
No
Step 54
Step 30
18 Engine stopped
Master off
Make sure that wires are hooked back up to the alternator - "F1" to "FLD" terminal and "R1" to relay terminal. Replace the voltage regulator and put "A1" wire on "A1" or "POS" terminal (with new style regulator, hook up to "B"). Continue Step 53
19   Check for a ground on "NEG" of the voltage regulator ("G" on the new regulator) located in the #3 baggage compartment. Yes
No
Step 7
Step 49
20 Engine stopped
Master off
Remove wire "F1" from the "FLD" terminal on the alternator. Meter the resistance of "FLD" terminal. It should meter 3 to 5 ohms of resistance. Yes
No
Step 42
Step 21
21 Engine stopped
Master off
Main disconnect off
Change out the alternator and the voltage regulator. Continue Step 23
22 Engine stopped
Master off
Main disconnect off
Change out the alternator. Continue Step 23
23   After installing new alternator, pull the field relay located in the rear electrical box and run engine for five minutes. Stop engine and plug in the field relay. Continue Step 52
24   Prior to unit #47071 - Check for a ground from the low air switch located in the rear electrical box. Effective with unit #47471 - Check ground studs located in the rear electrical box. Yes
No
Step 10
Step 25
25   Prior to unit #47071 - Replace low air switch located in the rear electrical box. Effective with unit # 47071 - Clean and repair ground studs located in the rear electrical box. Continue Step 10
26   Push the press to test button and see if the "no gen" tell tale comes on at the dash. Yes
No
Step 2
Step 27
27   Replace light bulb (part #19-11-1105) in the tell tale cluster at the dash. Yes
No
Step 26
Step 28
28 Engine stopped
Master on
Check for 24 volts on pin #1 of the discharge and blower relay located in the rear electrical box. Yes
No
Step 32
Step 29
29   Check circuit breaker #54 (load side) for 24 volts on the master buss bar located in the rear electrical box. Yes
No
Step 45
Step 31
30 Engine running Check relay terminal on alternator for 12 volts. Yes
No
Step 10
Step 22
31   Remove and replace circuit breaker #54 located in the rear electrical box; part #7C-13-127. Continue Step 28
32 Engine stopped
Master on
Check pin #4 of the discharge and blower relay located in the rear electrical box for 24 volts. Yes
No
Step 36
Step 11
33 Engine stopped
Master on
Check for 24 volts on pin #7 on the field relay located in the rear electrical box. Yes
No
Step 34
Step 51
34 Engine stopped
Master off
Check pin #2 on the field relay located in the rear electrical box for a ground. Yes
No
Step 35
Step 39
35   Check the field relay terminals located in the rear electrical box, and replace field relay, part #7D-5-24. Continue Step 36
36 Engine stopped
Master on
Check for 24 volts on stud #49 located in the rear electrical box. Yes
No
Step 54
Step 12
37   Check for 24 volts on battery buss bar on the load side of circuit breaker "A" (15 amp) located in the rear electrical box. Yes
No
Step 46
Step 40
38   Check for power on circuit breaker "A" (load side) on battery buss bar located in the rear electrical box. Yes
No
Step 48
Step 45
39 Engine stopped
Master off
Check stud #47 located in the rear electrical box for ground. Yes
No
Step 47
Step 41
40   Remove and replace circuit breaker "A", part #7C-13-127, located in the rear electrical box. Continue Step 36
41   Remove and replace triple function protective device located in the rear electrical box. Continue Step 36
42   Repair or replace harness from the voltage regulator to stud #48 located in the rear electrical box to alternator "FLD" terminal. Continue Step 18
43   Repair or replace the jumper wire with diode assembly from stud #33 located in the rear electrical box to pin #2 on the blower discharge and cut-in relay. Continue Step 54
44   Repair or replace harness from relay terminal of the alternator to stud #33 located in the rear electrical box and F1 terminal of the alternator to stud #48 in the rear electrical box. Continue Step 54
45   Repair or replace jumper from circuit breaker #54 located in the rear electrical box to pin #1 on discharge and blower relay. Continue Step 28
46   Repair or replace the jumper from circuit breaker "A" located in the rear electrical box to field relay pin #'s 8 & 1. Continue Step 13
47   Repair or replace jumper wire from pin #2 on the field relay located in the rear electrical box to stud #47. Continue Step 36
48   Repair or replace wire from circuit breaker "A" on the battery buss bar located in the rear electrical box to pin #'s 1 & 8 on field relay. Continue Step 12
49   Repair or replace harness from stud #49 located in the rear electrical box to voltage regulator "A1" terminal; stud #48 in the rear electrical box to "F1" terminal on voltage regulator; and ground stud in the rear electrical box to "NEG" on voltage regulator and jumper to mounting box. Continue Step 6
50   In the rear electrical box, repair or replace jumper between field relay pin #'s 3 & 6 and stud #49. Continue Step 36
51   Repair or replace jumper between studs 24 & 25 located in the rear electrical box and pin #7 on field relay. Continue Step 36
52 Engine running Measure the voltage on "R1" terminal of the alternator for 12 volts. Yes
No
Step 44
Step 22
53 Engine stopped
Master on
Check "FLD" terminal on alternator for battery voltage. Yes
No
Step 15
Step 44
54 Engine running on fast idle and charging
Head lights and exterior lights on
Check or adjust the voltage regulator to 27.5 volts. Yes
No
Step 55
Step 1
55   Make sure that all clamps, terminals, relays and covers are secured.   Job Done

This generator check-out guide was created from extensive research conducted by Lanny Martin. If you have any questions, please call the MCI Customer Support Center at (800) 241-2947.

Motor Coach Industries - A New Flyer company: Corporate Address 200 East Oakton Street, Des Plaines, Illinois 60018 | Phone: 866-MCICOACH

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