Pre heater wiring

[DHartley]

hey another newbie here i have not seen any info on wiring the engine pre heater,i am thinking the early non computer trucks will have a harness and timed relay? that i can copy /rob. any thoughts? also i have hydroboost but am considering using the vaccumm to run the brakes to clean up under the hood {no hoses} any one who can give me comparison info good bad etc thx Dana ps THis is a 97 215 motor nv4500 and early 205 going into an 84 chev cc 4x4 dually

 

[HoleshotHolset]

Welcome to the TDR!



Even the early model trucks have an ECM that controls the operation of the grid heaters. In all honesty, you could just wire a momentary switch to activate a relay that would fire off the grid heaters. The ECM will (depending on how early/late model it is... ) fire the grid heaters based on coolant temp and/or ambient air temp. The later model ECMs fire the grid heaters even when it is quite warm outside (and with warm coolant temps) to help keep the emissions down and smooth out the engine.



I have owned and driven many Cummins/Dodge trucks with both vacuum and hydroboost assisted brakes. Honestly, they're both OK in my book. The hydroboost brakes seem to create a more firm pedal and better feedback... but my vacuum assist '94 Dodge stops just fine and always has.



For the sake of simplicity and reliability - you can't go wrong with vacuum assisted brakes. The only downside is that with a diesel you need a vacuum pump in good working order to make it work...



Matt

 

[DHartley]

Matt thx for the reply, can you tell me if the ecm to control the heat is stand alone for early or late styles ie something that i can rob ? wiring up a manuel one is no problem but i like the auto system[call me lazy] i imagine there are timed relays out there i will do some digging,its just that modding an existing system might be easiest. As for the brakes i must have a working vaccumm pump to run my ac controls so unless someone can give me a reason not to i like the cleaner look of the vaccumm system. THX Dana

 

[Paychk]

The 89-91. 5 trucks had a control box that mounted on the firewall near the brake booster(I think). It is a small rectangular box with 2 triangle shaped mounting ears that have a single bolt in each, the ears are on the short side of the rectangle. It is standalone, so it will be easy to retrofit to other apps.

 

[HoleshotHolset]

The 89-91. 5 trucks had a control box that mounted on the firewall near the brake booster...

That sounds like what the mechanical 6. 2L's had on them for a glow plug controller. Those are pretty cheap and easy to retrofit for other applications.



Matt

 

[RyanB]

Are alot of guys just not going full manual though with the grid heater system? I am trying to figure out what I am going to do and seeing I am just driving this in the spring/summer/fall and its only going to have 14. 5:1 compression I am going to need the heat but I think I am still going to have to give it a shot of either to get it going on the cooler days. If it lands up being that way I will just get a toggle switch to turn them on and off and so they arn't on when the either goes thru!



If I were to do a full manual control how abouts would you wire this? Can I just put 12volts right thru the switch to the grids? and forget about the relays?



Thanks in advance... Ryan

 

[B.G. Smith]

Are alot of guys just not going full manual though with the grid heater system? I am trying to figure out what I am going to do and seeing I am just driving this in the spring/summer/fall and its only going to have 14. 5:1 compression I am going to need the heat but I think I am still going to have to give it a shot of either to get it going on the cooler days. If it lands up being that way I will just get a toggle switch to turn them on and off and so they arn't on when the either goes thru!



If I were to do a full manual control how abouts would you wire this? Can I just put 12volts right thru the switch to the grids? and forget about the relays?



Thanks in advance... Ryan

The grid heaters are a big time amp draw, the wire size is #6 from battery to relays and relays to the heaters. The alternator output on my truck is like 195 amps and when the heaters are on it can't keep up. You definitely need relays and put them on a momentary switch as suggested above, don't want to forget and leave those on and I would try to stay away from the ether, nothing good can come from using it. Unles you are in extreme cold climate you won't need it, tis is a Cummins you are starting, not a V/8-71 Detroit. bg

 

[RyanB]

Thinking about it and what you said you are right about the relays... just going to have to try to figure out how to wire this all out.



As far as the either... yeah chances are I am going to need it even in the cool temps of the summer. I am getting my engine built with Low-comp pistons and a full "truck Pull" cam. Compression will be down to mid 14's from the stock 18. 5:1 or close to it anyway. It won't quite be as bad as the mod pullers are (haisleys or any of the other big boys!) where they need two people just to start it but it will still need a little kick I think to get it going.



anyway, back to the grid heaters... . anyone have a wiring diagram available.



Thanks... Ryan

 

[B.G. Smith]

The wiring is pretty straight forward, one side of the grid heaters is grounded at the monifold, the other side is connected to the relay. On my truck, they use a relay that has both ends of the pull in coil run to the outside, one end is tied to the PCM and the other is grounded. The relays look like something you would find on an outboard motor for the starting relay. If you go the manual route you can use either type relay (one with one end of the pull in coil grounded or the type that is original equipment). You will need to fuse the feed from the battery and the switch circuit. bg

 

[HoleshotHolset]

Here's a quick-n-dirty wiring diagram I just whipped up.



As shown - when possible, I like to switch the ground that feeds the relay (instead of the hot lead... )... less chance of stuff shorting out.



Matt