Club 80-90 Forums

Last year my Propex started to play up. It would spin up the fan but fail to light. The gas would light with a "pop", shoot flame out the exhaust and then it would go out. I had a poke around underneath. (where Autohomes in their wisdom fitted it thirty years ago.) Let's say the time and road salt hadn't been kind to it. The case was rotten and I ended up bodging a bit of a video recorder's case over it to keep the water out and gave up with any repair plans.

Yesterday I was chatting to the owner of the garage who does some work on the van now and again. I noticed an orange box in the pile of scrap metal by their front door. It turned out to be a Propex they had pulled off a van with a supposedly burnt out fan. I said I'd like to have the it for the case and they said I could take it.

Today I managed to remove the original unit from my van and discovered swapping the case isn't that straight forward thanks to assorted spot welds and the progress of the rust. I'm now hoping I can make one working unit out of the two. The two units look basically the same internally but the circuitry is slightly different. I guess the "new" one is a bit more modern?


Rotten unit


"New " unit

Before tearing apart the one I got yesterday I decided to try to test it. I plugged a 12v feed to the fan motor and it spun up without any obvious problems. Next I put a feed to the gas solenoid and that clicked away happily. When I put a 12v feed to the main power lead all that happens is the green light (burner on) comes on. The yellow wires in the middle of this photo are connected to a small black solid state "switch" between the control box and the fan motor. Does anyone know what this is?



Does anyone have a wiring diagram or a test procedure so I can check it out properly?

I think I'm making progress and might have a working Propex again by this time tomorrow. As both units seem to have all the major bits working, fan, igniter, and gas solenoid I decided to experiment with the rusty X1 heater first.



There was nothing obviously wrong with the control board and thanks to google I managed to work out what most of the bits actually do. Just in case it's useful for any one else.

The black "switch" I mentioned in the first post (not in this photo) is a thermal cut-out, it's marked Otter C65 I think. If the temp in the box gets over 60-65'c it switches the heater off.

In the photo above are two black chips with 8 legs each. One of these is a 555 timer and the other is a 741 op-amp I think. I think the timer just lets the heater run for about 15 seconds before powering off. I guess the amp takes the signal from the blue wire that goes to the burner unit and uses it to keep the fan and gas solenoid powered as long as there is a flame. If the flame goes out the amp loses its signal and the gas solenoid shuts off and the fan stops.

This afternoon by checking the voltages around the board I noticed that one of the contactors (on the right of the photo) was moving and clicking but not putting out a voltage. I cleaned up the contact and closed the gap between the contactor arms and this time everything started up. After 15 seconds because there was no gas connected everything switched off. I know the newer Propex heaters have cooling cycles etc but I'm pretty sure mine justed stopped as soon as it was switched off. It doesn't have a thermostat or a cool air only setting.

Now I had a working board I took it out of the X1 and fitted it to the "new" heater. Everything seems to work like it should.
I've given the surface rust on the case a coat of zinc primer and hopefully I'll get it bolted back under the van and see if it will actually light the gas tomorrow.

Was going to say overheat stat, then found you've worked it out. Well done getting it working

The van has got heating again

I screwed it back under the van again this morning. After checking for gas leaks I flicked the switch and it lit & ran first time. All I've got to do now is find a better way of weather-proofing it than Autohomes did 30 years ago.