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OTR Central A/C -heat issue
We’ve recent experienced a problem with our OTR taking it out of service. When the “A/C – heat” switch is flipped to either the “A/C” position or the “Heat” position, an audible alarm sounds, the dash voltmeter bottoms out momentarily, and several dash lights flash (including the stop and check engine lights). Engine rpms automatically drop from high idle to low idle when the toggle switch is moved. Both the condenser and evaporator motors seem to operate without any obvious signs of an issue.
I’ve checked for a loose or heat damaged cable, replaced both motor relays, and visually checked the motor brushes. One of the circuit breakers was replaced about two years ago, the other last fall. Any suggestions would be appreciated!
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5 Replies
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Replace the ignition switch.
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With what you describe you have a tremendous load put on the electrical system when you turn on the a/c or the heat side. When you hit the a/c side you turn on both of the large motors that draw about 60 amps. each. With the heat you have only the one motor for heat air flow. Check the generator output when you put the switch on. The generator may not be aboe to keep up with hte load and the system voltage drops enough that you get the alarms and the variuos systems dipping. It appears that the problem goes away after this initial event. Correct?
Check the cable connections on the generator and on the batteries especially the gound cable. You could have a lot of corrosion and it could cause this poor current flow under load. Check the connections on the voltage regulator for the generator as it is external. It may not be able to respond to the load requirements.
If you have an clip-on ammeter, check the draws on the two large motors. Some where we have device not able to keep up or bad connections on the heavy load items.
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Thank you Boateral and Prevost Service. Those are great suggestions and we’ll explore them immediately!
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We finally have the OTR heat/ac issue resolved. It wasn’t a loose ground, a loose battery connection, nor an ignition issue…it was an intermittent battery problem. Scheduled replacement of the group 31 chassis batteries and the problem has gone away.
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This is instructional in the sense it highlights the grief and expense often associated with batteries that go bad, or are going bad. I don’t know if these were new defective batteries or aging batteries at the end of life, but from the description of the problem and what was involved in chasing it down it becomes another example of how we are dependent on good strong batteries for both the house and chassis.
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