View Full Version : TR6 Pressure testing a TR6 Heater core

01-28-2007, 05:26 PM

Does anyone know what pressure to test for leaks on a TR6 heater core?


01-28-2007, 06:12 PM
The cooling system is pressurized to 13 lbs. That said, I took my core to a local shop who boiled, pressure tested, and inspected the unit for $20. What a deal.

An aside note. When I asked them about painting the unit, they strongly recommended against it since you cannot get all the surfaces painted. In their opinion, all you accomplish is painting the outside and leaving over spray on the inside to capture dust and dirt.


01-28-2007, 06:25 PM
2 saw bucks is a deal. If you aren't in the market for a new heater core, try this avenue. However, I am of the opinion that if you have the heater out on a TR6, then by darn, change everything for new, you DON'T want to repeat that chore. You will kick yourself if something fails next month.

I just redid my heater and I replaced everything but the rheostat resistor bar for the fan speed. I was told my someone in great authority (Dave at TRF) that he has never seen one of these buggers go out. He said they almost never, or even never, sell one.

Mine went out.

I performed arthroscopic surgery on my heater in situ. I used some dental tools to snip the wires off the bar and ran a new wire direct to the high end of the bar and simply bypassed the rheostat. I only operate on high speed. But have you ever seen a TR6 heater that was worth anything on low speed?

Have I talked you into buying a new heater core yet?

01-28-2007, 08:10 PM
Ray & Bill,

Thanks. Has anyone ever tried rebuilding their core at home using TRF components?

01-28-2007, 08:14 PM
Daniel, I'm not quite sure what you mean, using TRF components.
To my knowledge, The Roadster Factory, nor anyone else sells components for the heater core. At least this is what it sounds like you are saying. TRF does well new heater cores, which I bought one and installed.

Are you referring to the whole heater unit as a heater core?
The heater core is the little radiator inside the unit.

The only parts not currently available are new fans. I found one on ebay some time back.

Are we on the same page?

01-28-2007, 09:26 PM

I was referring to the entire unit as the heater core. Thanks for the correction. I had seen where TRF was selling new fans and heater cores for at home rebuilds.

Anyway, I just bench tested my unit with 12V and I couldn't get the fan working...until I gave the fan blade a little help getting started by giving it a slight twirl. And this was at full voltage. It wouldn't even turn on the lower voltage wire.

I guess the wisest thing to do would be to replace the entire unit and KNOW it is good.

As always,

Thanks for your advice!


01-28-2007, 09:36 PM
I bought a new TRF heater motor, which I had installed in my TR6 when the tranny was out this spring. My original was seized. Since then, I've located two very nice complete heater assemblies on ebay, which I am preparing to disassemble and rebuild. I just ordered the new grommet packages from TRF and will take the cases to be powder coated when they're all apart.

The cores will go to a local shop to be cleaned and recored. The motors seems to be fine, but will go to my buddies at Yankee Auto Electric for disassembly and testing.

The resistor is the only item not available at this time. I may take a spare two speed switch along with the motor to see if they can find me a switch that will have the same style shaft, or interchange them, so that I can get a variable switch that does not rely on the resistor.

For the most part, Lucas electrical parts get a bad rap, but putting a resistor that is prone to failure inside a case that requires dash disassembly to remove is beyond dumb. Smith's heater engineers were sleeping when that design was approved.

I plan to do a pictorial for those who are planning to do the job. I will not be tearing he car apart at this time, but everyone will see what the heater case and cores are about.

01-28-2007, 09:43 PM
The only way that you will KNOW that a rebuilt unit is good is to test it PRIOR to installing. Hook up your switch to a power supply and run both speeds to insure that the resistor is not blown. These have not been available for years, so even if you buy an assembly, which Dave at TRF told me months ago were no longer available, you will not be getting a new resistor.

Remember Mulder's wall poster in the X-Files; "Trust No One"

Except dear sweet Dana Scully..............

01-28-2007, 11:57 PM
Ok...please check my logic if this would work:

If the assemblies are NLA, then I can have a local radiator shop renew the core, bead blast the housing and powder paint it, buy a new electrical motor from TRF and just live with one speed?

When taking the cases apart, are these just screwed or riveted or is any welding involved?


01-29-2007, 08:51 AM
I meant that the resistors are no longer listed or available according to Dave. However, last night I found two numbers in my old green TRF catalog, that I want to ask them about when Level II opens this morning.

The cases are originally riveted together. Simply a matter of drilling out about (8) rivets with a 1/8" bit and knocking the heads off. The heater motor frame plate bolts onto the riveted plate with (3) bolts.

I have two used assemblies, one is riveted and one has screws. I'd be willing to bet that I find a newer motor or core in the screwed together case. If you can wait until tonight, I'll take some pictures, post them to my website and to this thread and I will show what the case looks like when apart.

TRF advertises that they would take your assembly and do what you and I are planning to do for about $350 with used parts or $399 for new. They will only paint the cases with enamel, not powder coat. https://www.zeni.net/trf/TR6-250GC/43.php

01-29-2007, 09:43 AM
I just confirmed with Tim at TRF that the cores are in short supply, one left and the motors will not be in for several weeks. Resistors are no longer available.

Now I know for sure that I'm going to work on a different switch arrangement.

Andrew Mace
01-29-2007, 10:19 AM
...For the most part, Lucas electrical parts get a bad rap, but putting a resistor that is prone to failure inside a case that requires dash disassembly to remove is beyond dumb. Smith's heater engineers were sleeping when that design was approved....Having heard tell from a first-hand source (nearly 50-year Lucas employee) that British Leyland in particular did their best to demand suppliers provide parts more to a price rather than to a quality, I suppose there is a grain of truth to the "legend" of British electrical system quality. In fairness, though, we're discussing here a 30-year-old + component on a car designed back when a 10-year product life cycle was probably the maximum.

Trying doing similar jobs on a more modern car such as a Honda or Toyota. I was thrilled by the fact that the heater core of my long-gone '91 Ford Explorer could be changed without removing half the car to get at it! That was especially good, since that beast went through four heater cores in 12 years! But that seems to be more an exception. Thankfully, the heater core in my daughter's '92 Toyota Paseo is still functional, but it looks as if I'll be replacing the heater blower motor. THAT job appears to be somewhere between nightmare and...uh...never mind. It will NOT be fun. /bcforum/images/%%GRAEMLIN_URL%%/frown.gif

But I readily admit that what I love most about these old Triumphs is the relative simplicity. Granted, the Toyota does have a much more powerful and efficient heater, but with that comes a motor buried deep under the dash, behind various A/C bits, and controlled by a multi-position switch AND a resistor unit of some sort behind that switch...AND a n electrical relay that may actually operate the blower motor somehow. My Herald? One toggle switch turns on the heater. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

Paul Johnson
01-29-2007, 10:33 AM
But have you ever seen a TR6 heater that was worth anything on low speed?

Interesting. The heater on mine is first rate, but I don't know if the core is stock. Yesterday I drove about 100 miles with temps in the low 30s. The heater water valve was barely opened and I used no blower while at speed, turning on the low speed when back in town. It's been that way for the six years I've owned the car. Maybe though, I'm still just happy to be away from the 356C that, when you turned on the heater, all you got was warm air and lots of fumes.

01-29-2007, 05:10 PM
Having owned several early 60's VW's, that were used as winter "donut cars", I can relate to that remark. My 911 never had those issues. Sigh.......

I'm sure that the core is stock. No one would ever redesign a case to fit a bigger core, not even TR6 Bill or Kodanja!

TR6's all had good heaters, as long as you got all of the air out when you drained and refilled the system. Of course doing so almost always stopped the dreaded overheating issues as well.

Andrew Mace
01-29-2007, 05:53 PM
Frankly, I don't think a bigger core necessarily translates directly into a more powerful heater. The core in my (long gone, thankfully!) '91 Explorer isn't a whole lot larger than that in my Herald!

01-29-2007, 10:33 PM
I'm starting a new thread that will eventually lead you here for more pictures and details.


This one can remain for the answers to Daniel's further questions.

01-29-2007, 11:00 PM
Hi Paul,
I was able to get the heater core out and the fan blade off without breaking the fan. Mine had only a rectangular friction clip retaining the fan blade to the motor shaft. Anyway, I'll get my heater core checked out at a local radiator shop. As for the motor, It only works with the full voltage lead...even then, it runs rather slowly. Is it worth while to have a local motor shop rebuild this motor?

I'd be really interested in knowing how you finalize your switch set up for getting two speeds on your motor.

Many thanks,