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MG TD TF 1500 - Heater Installation

I have acquired a used period Smiths heater and am trying to determine the method of installation. There are no brackets included, so fashioning one is something I'll need to do. Checking the archives brings up a few questions though.

First, I see that many have chosen either initially or eventually to avoid a rheostat, as the heater is on high most of the time anyway, and use an on/off switch. My question is with both the need for a relay with the switch, and a control/shutoff valve. I assume that with a relay (and fuse), I am protecting the electrical circuit, and with the control/shutoff valve, I am keeping the hot water out of the core during the warmer months. So, my questions:

1. I have no need to control the flow from the cockpit. Can I just install a shutoff valve in the heater inlet hose? I assume the hose coming from the back of the head (mine is plumbed there from a PO) is the inlet hose. I know it's not the hottest place, but it's fine for Texas.

2. Where should I wire the switch, fuse and relay to the electrical system to have "switched power?" A4 of the fuse block? Or, is there a better place besides the ignition switch itself? Or, is unswitched power OK?

3. Anyone have p/n's for a manually controlled shutoff valve and relay?

Any and all advice is appreciated.

TIA

Larry
L Karpman

I took my power directly from the battery and fused the wire.... My shutoff valve was a 1/2" brass fitting from the local hardware store.....it is fitted just before the hose enters the firewall....I turn it off in the summer by opening the hood....
I have an on/off switch and leave the rheostat on high.

No part numbers...just hardware stuff.
gblawson

Larry, you might want to take look at http://www.ttalk.info/Lazarus%20Heater.htm
Bud
Bud Krueger

Larry

If you don't have a pattern for the hanger bracket, I can do measurements and pictures of mine. It is out of the car so easy to do.

Bruce
BEC Cunha

hello larry, if you want a car part for the shut off. moss sells the shut off used on the tr3's. for my smiths heater i just cut a 3/8" piece of plywood, painted it flat black, bolted the heater to it. i hung the heater from the tub cross brace tube. the tube just above the transmission tunnel...just forward of the shifter. i used a pair of adel clamps to hang the heater. adel clamps are rubber lined aviation clamps. you can order them from various aviation hardware supply houses. i used a tr3 heater firewall fitting sold by moss to go through the firewall. regards, tom
tom peterson

Thanks for the responses to all. Gordon thanks for your input, as usual. Bud, your page was also helpful, and Bruce I will take you up on your offer, so I'll look forward to your posting. Tom, the TR3 heater valve (635-120) appears to be a manual control, not a push/pull device. Is this correct? Also, how did you mount the valve?

Thanks again

Larry
L Karpman

I also hung a piece of ply from the cross brace and added a steel bar I made going back to the firewall to keep it from rotating.... If you have a way to get the ply back a few inches (instead of hanging straight down from the brace) you won't run the risk of catching the doors when you shift...At least with my heater...

...maybe I should post 'Test the shifting before you bolt it down'
gblawson

Larry,

You only need to valve the inlet, the outlet will take care of itself.

Your relay will provide much better power to the heater fan as its contacts are more reliable than a small switch, and it can handle more current than a small switch. Basically the relay gets a big current wire, and is switched on by a small current that comes from the small switch.

However, in this case, I can't imagine the small heater fan pulling so much power that the switch ends up being a problem. I may be inclined to wire the fan without a relay if you just pull power off the battery fuse it, go to the fan, and then take the ground to the switch, as nearly every circuit on the car is switched to ground. You will have to remember to switch off your fan as the car's ignition won't in this case.

If you use A4 which is switched and fused already, A4 is carrying a bit of a load, and using A4 to power the switching side of your relay, and then to the switch and then to ground, will keep the current requirements of A4 fuse well within its limits since the majority of the current used will be coming from the main battery to the relay to the fan and then to ground. In that case, fuse the main line from the battery to the relay. Now you can turn off your car and the fan will be off too. One convenient place to get A4 power is from the turn signal flasher as it is switched and fused and comes directly from A4.

I hope this helps,
dave
Dave Braun

I'll update my thoughts after talking with another MG'er by pointing out that if you take the power for the heater off the ammeter, you'll know what your amperage use is. So either take the power from A4 to fire a relay that gets its power from the other side of the ammeter; or wire from the ammeter to a fuse directly to the fan and go to the switch, and then ground. Going directly from the battery bypasses the ammeter.

warmly,
dave

Dave Braun

Dave. Forgive my "electrically challenged" question here. You said, "...if you just pull power off the battery fuse it, go to the fan, and then take the ground to the switch, as nearly every circuit on the car is switched to ground."

Maybe I'm not understanding, or I've been wiring accessories wrong, but normally I do the following: If I have an accessory, say a driving lamp controlled by a separate 2 pole Lucas switch, I have one wire from the lamp to ground, the other from the lamp thru a fuse to the switch, and the other wire from the switch to the power source. Therefore I am completing the connection at the switch using the hot wire. Sounds like you are telling me to make the heater unit electrical connection at the switch with the ground wire. Am I doing incorrect wiring?

TIA

Larry
L Karpman

hello larry, i did not put in a shut off valve. i noted the tr3 valve when i was researching parts. i thought i would add it if i ever felt the need. so far...no need. for what it is worth, using the correct adel clamp for installation requires NO mods to the car for mounting and keeps the heater in place. the tr3 firewall fitting for the hoses makes it a very clean, neat installation under the bonnet. regards, tom
tom peterson

Thanks Tom. I'll probably just use a standard plumbing valve if I use one. The holes in my firewall are already there from a PO, but they are rough and I'm not sure how I'll deal with that. Still concerned about the proper way to wire this, as I was confused by Dave B.'s instructions. Being dumb on electronics as I am is not helpful :-)

Cheers

Larry
L Karpman

Larry,
Hopefully, this might help. The TD-TFs were originally positive ground. On the TF the power to the windscreen wiper motor comes from the negative (or “live”) side of the battery, there is no switch on that side of the circuit. Thus there is always power “flowing” to the wiper motor, but the motor will only run when the circuit is complete and that occurs when the motor is grounded. There is a double wire that runs from the wiper motor to a very primitive contact switch that is attached to one of the two wiper control knobs. When the knob is pushed in, contact is made and the wiper motor is grounded and the motor starts to run.
David Werblow

David: Yes I agree, but my heater fan is a single wire which connects to power, and the heater case itself must be grounded to complete the circuit. If I mount the heater to the tub cross brace below the dash with metal brackets, it's going to be grounded and run all the time, unless I run the "hot" wire thru the switch which prevents power to the unit when the switch is in the off position.

Larry
L Karpman

larry, on my smiths i had two wires. i tapped off switched power, put an inline fuse and a switch in that wire and ran the ground wire to ground. regards, tom
tom peterson

I woke-up in the middle of the night thinking that I’m wrong! If the power in an automotive circuit runs from the positive terminal to the negative terminal of the battery, then on a positive ground/earth system, the power would flow from the ground into the wire harness and its related accessories. So any accessory not grounded will not get power. Of course if it is grounded but not connected to the wire harness the item won’t work either.

David Werblow

You got it... now, which wire do you put the fuse on?
gblawson

....on a positive ground car, the power goes through the body/frame/metal and up the ground wire to the accessory, then back to the switch, then to the fuse box, then back to the battery.....???
gblawson

Larry,

If indeed you only have a single wire coming from the fan, and the fan case is grounded, then wire the switch to the single wire, and ground the case as you suggested.

warmly,
dave
Dave Braun

If you look at the wiring diagram for the TF you will see that there is NO switch in either the green wire from the fuse box to the screenwiper or in the wire from the motor to ground. However, they did actually install a switch in the ground wire that is activated by the control knob. In the TD there is not switch in either of the two wires (green & black) leading to the screenwiper but in that case the switch is in the screenwiper itself.
David Werblow

Thanks All. Tom, I will do the same, except as I have no ground wire from the motor (it apparently is grounded to the case) I will connect and fuse the hot wire from power to the switch, then from the switch to the single hot wire on the motor, and let the case be grounded via the mounts to the frame. If I choose a mounting system that doesn't ground the case, I'll run a ground wire from the case to ground.

To my "very basic" knowledge, it should not matter if a car is pos. or neg ground. to determine whether to switch the hot wire or the ground wire. I believe placing a switch in either wire will work to turn power on and off. My '53 TD is converted to neg. ground, and as most of my added accessories are switched and fused thru the pos. hot wires, I may be driving around a rolling time bomb if I'm wrong :-) Some one let me know :-)

Cheers

Larry
L Karpman

larry, i am not sure if you rebuilt this heater/fan..if not does it run well on the bench? regards, tom
tom peterson

Tom. I bought it used, and it appears to work fine when connected to power. Fan blows air out of the doors, but it's not the quietest fan. No rattles, just loud. I plan on taking it to my radiator shop and have them test the core for leaks.

Larry
L Karpman

Just fill it up using one of the copper pipes and let it sit for an hour...oh, your pressurized...yep, take it to the rad shop....
A drop of oil on the fan shaft may fix the noise...did on my first one.
gblawson

Thanks Gordon. Not pressurized ('53 TD), so I can do it as you suggest, but my buddy at the rad shop will do it no charge if I wish.

I did some more inspection of the unit. There is a ground wire for the motor inside that is attached to the case by a screw. So I suppose I could disconnect that and wire the ground any way I choose. We'll see.

Cheers

Larry
L Karpman

The idea that "power" (actually current) flows from the positive terminal of a battery thru the circuit to the negative terminal is a fiction created by Ben Franklin to explain his theory of electricity. In his theory all matter is filled with an invisible electrical fluid, A current of electrical fluid will flow from a place that has an excess of electrical fluid ( + for excess terminal) to a place that has less electric fluid (-). He did not know about positive and negative charge electrons) and that the negative charges were what was moving to make the current. In effect he just pointed to a terminal on his equivalent of the battery (a capacitor) and said that current comes out here (positive or excess) and goes in there (negative or less). He was right if it was positive charges that made up the current, but he was exactly wrong since negative charges (electrons) actually are the current (they weren't identified for another 75 years.) Physics still uses the convention of Positive current flow.

For us and our T's, wire from someplace hot (the ungrounded terminal of the battery for example), thru a fuse (if needed) thru a switch to the fan (or whatever) to a good chassis ground. The circuit is then completed from chassis to the battery ground strap,
Don Harmer

Thanks, Don,
It is only fitting that as a T-type owner that Ben Franklin should be my authority on things electrical. Surely his theory that all matter is filled with an invisible electrical fluid is correct. We all have experienced what happens when this fluid escapes from its wiring system and is exposed to air—instant visible vaporization. ;)

Have a good Christmas, everyone!
David Werblow

Ok Larry. I took pictures and measurements of the bracket. I posted them here

http://community.webshots.com/myphotos?action=refreshPhotos&albumID=576035366&security=FMgQWb

Large plate is 6" wide x 5" high with a 90 degree bend at 2 1/2 inches on the 5" high side.

A 1 1/2 x 5 3/4 smaller bracket is welded so that 3 1/4 inch sticks out past the edge of the plate. This is welded so there is a gap of 1/2 inch from the weld to the edge of the plate. This space is used to attach the heater to the lip on the bottom of the tool box.

There is a 1/4" hole centered 3" out from the edge of the plate. A bolt goes through this and the lower bracket through the bottom of the tool box.

The lower bracket is 9 inches long including 2 1" tabs that are bent at 45 degrees with 1/4" holes in each tab. This hooks to the lower bolt on the heater and up to the bolt coming through the tool box.
BEC Cunha

Link is not working correctly. Try this one for the bracket pictures

http://rides.webshots.com/album/576035366FMgQWb
BEC Cunha

Found another error. Small bracket should form a 1 1/2 inch space between the top bracket for the edge of the tool box.
BEC Cunha

Thanks Bruce! Great info, great pics. Thanks for taking the time. Although mine is not an Arnolt heater like yours, the bracket should work with some small mods to my case if I choose to go that route. Tom Peterson's method also is interesting and it's worth considering both methods.

Thanks again

Larry
L Karpman

Anyone have a front to an Arnolt heater that is languishing in a pile of junk?
I have 2 Arnolts but one is missing the front panel. I'm at the crossroads of installing 1 complete or 2 with some modifications.
jrn Northrup

By the way, there is a complete Arnolt heater assy. on ebay
http://cgi.ebay.com/ebaymotors/MG-parts-used-orig-Arnolt-heater-assembly-MG-TD-TF_W0QQcmdZViewItemQQhashZitem4838be53acQQitemZ310189642668QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
I don't want to bid against other club members.
jrn Northrup

Larry

Principle of how the arnolt attaches should work similarly for other heaters
BEC Cunha

This thread was discussed between 22/12/2009 and 24/12/2009

MG TD TF 1500 index

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