Summer is here - It's heating up - the aircon becomes more important - if you live in the tropics, as I do, it is REALLY important.
Since I bought my 88, nearly 3 years ago, I have been working on several aspects of the aircon. I just had a big win, with constant vent temps of 6.6C to 7.7C while outside road temps were showing 33C - so before something else goes wrong here's my report -
My vette was converted to R134 gas during the Corvette Qld conversion about 8 years ago. It has the C68 climate control. When I bought the car 3 years ago, I disconnected the heater hoses, to maximise the efficiency of the aircon. Since then, I have been working on getting the aircon more efficient.
I was disappointed with the airflow from the blower - I bought a new blower from Dave at Pontiworld – very good value, and it drew less amps than the old blower, but the airflow was disappointingly the same - about half what’s needed.
I took the dash apart - found a beerbottle top, half blocking a disconnected airvent tube, and a few other problems like that. The Airbox is moved from RH to LH side during the conversion and also inverted. I cleaned out the evaporator because when new, they have a sheet of foam in front of them and this melts/deteriorates over time, especially in hot climates. I fixed several air leaks from poorly sealed joins etc.
I fitted a dual digital thermometer, from Dick Smith Electronics, so I could measure the centre vent temperature and the cabin temps – and get an accurate view of what was happening.
The aircon kept the car coolish but never cold enough. There is an adjustable inline screw, beside the evaporator box, that sets the low pressure going into the evaporator. In my attempts to get colder air, I have turned it down very low, (anticlockwise,1/2 turn) but the evaporator iced up. The signs were the vent temps going from a nice 9 or 10C and rising to past 22C - always fixable by leaving the fan on and turning A/C off so it could thaw out. I turned it the other way (1/2 turn clockwise) and the vent temps were not cold enough- 12 - 13C ,and still the evap eventually iced up, sometimes after an hours driving.
I also found that when the car was parked and hot, upon restarting, hot air would blow from the vent until the car was moving – the inline coolant fan switch was not working – it should turn the coolant fan on when the aircon is turned on, so that air flows across the accumulator, in front of the radiator –I fitted a manual switch to turn the fan on and this solved that problem – I recently ordered a new replacement switch from the US.
I had the gas checked this year, thinking I was low and needed topping up – but everything tested out OK. Recently I spent a few days chasing airleaks in the vent system .
The aircon box is in two halves and I found some major leaks on the engine side of the firewall, where the aircon box joins had split open. I also found two oblong section air tubes under the dash, venting air into the dash cavity – if they were a bit longer, that air might have reached the footwell, but the size of the pipe was too extravagant for the amount of moving air. First priority, for me, is to blow cool air on chest and face – then onto feet. So I partially blocked them –I also found the heater door was not closed, my previous fix not being good enough.
After I sealed these significant airleaks, full blower was now giving maybe 7 out of 10 airflow. I then discovered that this had cured the frozen evaporator problem – a huge and unexpected win. Here’s the details -
Last Sunday I saw the incredible vent temps of between 6.6 and 7.7C, and no icing up of the evaporator. Aircon mechanics are happy to set the vent temps at 10C so this is a significant achievement. I can only assume that fixing the airleaks and closing the heater door has increased the airflow through the evaporator and that has stopped it icing up.
I drove for 30 mins, at 8.30am - outside temps were 28C - I saw 10C vent temps within a few minutes - and it continued to lower until an amazing 6.6 then raised to 7.7 and then lowered back to 6.6, completing this cycle perhaps every 3-5 minutes. I saw it cycle like that at least 4 times - I was getting quite cold and had to point the vents away from me!!! WOW - no evaporator icing up!!!!
At 11.30am, the parked the car was very hot - over 55C I would guess - I opened the windows and hatch and waited until cabin temps were 46C. Road temps were 33C. It took the aircon most of the 30 min trip home to get the vent temps down to 10C - the seats and most things inside the car (including me) were still hot, but it was cooling down. (So I would still like to double the airflow – but it seems that all the fan motors are similar - according to an auto electrician - I'm looking for more revs.)
I started to think about the new cured icing problem - if increasing the flow through the evap has fixed the icing up, then it should ice up when I turn the fan to low.
That afternoon I drove for another 30mins. It was v hot, outside temps 33, so I left the aircon on max - and saw the same cycling between 6.6 and 7.7 – good confirmation that I may have a cure for the icing up evaporator.
On the way home, at dusk, I ran the aircon on max, till it went down to below 10C, then turned the blower down to 2. The vent temps stayed around 9-10C, and no signs of icing. I had expected the lesser airflow to re-create the usual scenario where the vent temps suddenly rise from around 9 or 10 to 22,which is what I assume is the evaporator icing up.
Strangely, there was still a more than expected amount of air coming out of the vent, I expected 2 to be very light. Next time I’ll try 1.
I reckon the heater door has not been closed for a long time, the way I originally wedged it was not very good. So maybe that is it? But I always got 9-10C vent temps before and it was always icing up at around 8.5 -9C. Does that mean that with most of the leaks sealed and the heater door closed, the evap now gets enough air through it, even on low fan speed?
I shall have to test this on a 1 or 2 hour drive before I can say all is well, and if it does eventually ice up may sneak the low pressure screw clockwise a very little bit.
Two other things I have discovered are – if the blower only blows full speed, an inline fuse, near the bulkhead has blown – I replaced mine with a 15 amp fuse and have had no further trouble.
Recently the blower was stuck on, even with the ignition key out - the blower module had failed. I bought a new one from Dave at Pontiworld for $212, once again good value - and the shipping was free. (Jeez Dave, if you’re reading this, I should be getting commission for all this advertising!). On LH drive cars, the module is on top of the aircon box, so on RH drive cars it’s on the bottom and not so easy to replace. I got some great help from the Corvette Forum, including two NSW Aussie vette owners – rodj and Aussie Vet
It's nice to get a bit of good news sometimes, and I thought I’d share this with the forum. I’d like to thank SunCr from the Corvette Forum for all the advice he’s given me – he knows the vette aircon inside out, but of course the RH Drive conversion can change a lot of factors.
S’nut
