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Algoma · 04-02-2009, 06:10 PM

While checking the ground fuse I noticed a problem with the grid heater relay. There are no wires connected to the relay coil. Evidently my grid heater is not working and never has since I've owned the coach. I cannot find any cut wires close by so I have no idea where the coil should be connected to.
Could someone with an older coach check their wiring and tell me where it connects to please.

Old Scout · 04-03-2009, 09:41 AM

Very interesting--havent looked at my 2003 but am sure the wiring is similar. Grid relay would have to wired to the ignition switch to accommodate the 10 sec pre-heat cycle between the on position and the engine start position--if you exceed the 10 sec pre-heat cycle before starting the engine, you must re-cycle by going from off to on position again. Not sure how the grid relay manages the 10 sec pre-heat cycle. Too obvious perhaps, but there are no extra wires hanging from the wiring bundle in front of/behind the plate where the grid relays are mounted?

Algoma · 04-03-2009, 10:04 AM

The large box in the picture is the "heater control module" which I assume connects to the ignition and a temperature probe somewhere. The "wait to start" light works and stays on longer in cooler weather so I guess the module is working. I am assuming there should be a connection from the module to the relay but there isn't, even behind the panel. Would be nice to get a wiring diagram for the module.
The chassis wiring diagram on the ACA tech. page shows 2 relays but I only have one so there may be some differences on how this works between the C engine I have and the ISL.

EngineerMike · 04-03-2009, 08:39 PM

Chassis wiring schematic, page 3 of 4, dated 3/25/00 shows two grid heater solenoids. They each have 4 studs, 2 small & 2 large. The small studs get ground from the engine's ECU 50 pin plug, pin #27, Grid1 is energized by pin #41 and Grid2 by #31. All this wiring is on the engine, and the ECU is mounted to the engine block, PS, just about the middle front to back and behind the diesel lift pump.
Of the large studs, one on each solenoid goes to a 125A fuse then to the heater. The other large studs each show a #6 red wire running to something called a "Cab Power Fuse" with the number 105 on it (105Amps?) and the pair of CPFs are fed by a red #2 wire direct from the Chassis Battery Disconnect switch.

If you trace the #2 from the CBD to the CPFs, you should find the 6ga red wires that go to the large hot studs on the GHSolenoids. A simpler exercise might be to check voltage across the large studs as a trusted chum turns the ingition switch on to see if the solenoid is getting energized t light the grid heater.
Hope this helps.

Algoma · 04-04-2009, 05:02 PM

Mike,
As I said previously I have a "C" engine which is not electronic and therefore I do not have an ECU. I have a separate control module for the grid heater. Power to my relay (only 1) does come from the Cab Power fuse (actually a 105A thermal breaker) but the control signal must come from the control module. I guess 2000 was a major change for the Alpine so I need info from a '98 or '99 coach. Thanks for trying to help.

EngineerMike · 04-05-2009, 10:38 AM

John- I was told, I think by Phil Mattoon, that all Alpines produced were electronic, and the 2000 schematic is for ISC engines. The ISL didn't come till later. If you have a non-electronic engine that would be news to me.
Do you have "common rail" fuel delivery, i.e. a pipe like extension off the injection pump along the length of the engine?

Algoma · 04-05-2009, 12:22 PM

Mike, My engine is a 6CTA 275HP. There is no common rail and another clue is that I have a separate cruise control box mounted to the frame made by Cruise King. I also have a PAC brake on the engine, not a Jake brake. Alpine stopped using these when they started installing the ISC/ISL engines. Cummins Atlantic confirmed this when I had it serviced. I have been through this with Mark Harrah and he agreed I am missing 2 wires but he couldn't tell me where they come from.
P.S. I didn't see the schematic you mentioned on the ACA tech. page.

EngineerMike · 04-05-2009, 12:32 PM

J- the schematic isn't up yet on ACA. It is in an 18"x24" format & the first scan I got was so rough that it isn't usable. I have to pursue higher resolution scan methods to get it into electronic format, which for the large format are not too common. I'll get it there.

It would be easy to set up a stand alone switch to operate the heater, tho it would be better to move the rig where it isn't needed (and of course, better still to get it wired as it should be). Does the solenoid have wire to any of the 4 studs?

Algoma · 04-05-2009, 02:48 PM

Like a large number of people we normally only use our coach in warm weather so starting without the heater hasn't been a problem. Except this January when we made a trip South and I had to start up in 10 degree weather. That's when I noticed the problem. Power is getting to the input side of the contact and the output goes to the heater via a fuse, there are just no wires connected to the small terminals to activate the relay.

EngineerMike · 04-05-2009, 03:57 PM

Perfect. Sounds like it came wired from Cummins for heater power, to be controlled by coach mfgr wiring. IIWM, I'd run one small stud to ground wherever it is convenient, and the other (with an inline fuse of about 5A) to a switch located by the rear panel of wiring devices & then to 12V. Then with the rear lid open I'd activate the switch manually, start engine, do a walk-around & shut off switch, then close the lid.

Some day when parked next to another 97 or 98 you can see how it is "supposed" to be wired (or maybe tht this feature was never activated?) and you can revise accordingly. One good thing, your grid solenoid should be good as new.

dgerstel · 04-05-2009, 09:08 PM

I like things to be automatic when possible. I would install a time delay relay like this one.

http://www.smarthome.com/manuals/7279.pdf

It could be wired to power the grid heater relay when the ignition is turned on and then would cut off the power after a time you set.

Old Scout · 04-06-2009, 07:43 AM

For my two cents--I agree with dgerstel and would be concerned about a manual solution overheating the grids. Its entirely possible that the existing relay[s] has a built-in time delay so maybe just a wire from an ignition-switchable source will get you back in business[you should be able to conduct a test of the relay to confirm a delay function.] If not, a manual switch on your dash would be easy enough to install and would allow you to simulate the delay--besides, this isnt something you need to use alot anyway.