Originally Posted by Aarcuda

so I’m revisiting this post I was a part of sometime ago because I was still having periodic problems with my air-conditioned car getting nothing but heat after driving for a while. If i shut it down came back sometime later, the air-conditioning would be perfect. No heat like before. But then after driving, for a bit id get the same problem- super hot heat on both sides.

I didn’t think it could be my climate control module because ccm had those resettable fuses installed by Jaguarclimatecontrol.com. Well, i think those resettable fuses gave me a false sense of security. I think.

I went through the whole system again earlier today and measured all sorts of values and made sure my voltages, currents and resistance values were correct and they appeared to be just fine.

I was worried because when I started having this problem, I replaced my DCCV. But I had installed a cheap $30 DCCV despite all the warnings about potential failures if I don’t get the OEM Bosch valve.

well, I went out and I measured the resistance of the solenoid coils in the DCCV and they were right on the money at 16 ohms apiece and 32ohms through both coils in series measured at the climate control module connector. I even measured the same value when I went to the FC4 chassis harness connector on the side of the instrument panel by the drivers door ( left side.)

I had correct system voltage at the center terminal on the valve so there’s only one more failure point that could’ve been causing my periodic heat. That’s inside the climate control module.

I said earlier that the low side switch inside the climate control module is extremely stout and I still believe it is. It has a 2000 V ESD protection. Overcurrent protection short circuit protection, 30 amp max capability for short period of time. Also usually when something like that burns out it burns out forever and doesn’t repair itself, and my problem is definitely periodic and it takes a while for it to happen after you start the car up so that points to something that trips and then goes back in service-like a resettable fuse maybe?

so that only leaves those damn resettable fuses shown earlier in this post. when I went to pull the data sheets on those resettable fuses, I found out something interesting- they don’t sell that value anymore. The parts that I have were marked G0 or 60. Its hard to make out. I believe it’s G0.

Looking at the little fuse catalog for PTC resetable fuses shows that the smallest value they sell now is marked G2.5, which has a 2.5 amp nominal current rating with a trip current of 4.7A. and that made me wonder if G2 .5 means 2.5 amp hold current and a 4.7A trip current, what the hell does G0 mean? How can they have a resettable fuse that has a 0A hold current? I sent an email to Little fuse to ask them about the specs to my devices and when I get an email back I’ll let everybody know what they say.

But in the short term, I am going to remove those resettable fuses and just jumper the burned out traces with a wire straight from the low side, switch straight to the connector pens and call it a day.

still interesting that nobody has found the reason for these traces to be burning up the way they are. I’m just going to assume that the traces on the climate control Module are just way under size for the potential current that can flow the resistance of the solenoid coils is between 13 and 20 ohms each, and as I said earlier, each of my coils appeared to be at 16 ohms individually or 32 ohms in series. So I’ve got about .85 A of current flowing, but if you quit resistance went down to 13 or even 10, you would get over one amp. Up to possibly 1.4 A at 10 ohms coil resistance

i’ll let y’all know what I find. Hopefully jumping straight to the low size switch fix my problems and if I hear back from Little fuse, I’ll let everybody know what a G0 resettable fuse trips at

The second the last column shows the part markings and you can see it starts at G2.5. so what is a G0?

Originally Posted by Aarcuda

I was worried because when I started having this problem, I replaced my DCCV. But I had installed a cheap $30 DCCV despite all the warnings about potential failures if I don’t get the OEM Bosch valve.

well, I went out and I measured the resistance of the solenoid coils in the DCCV and they were right on the money at 16 ohms apiece and 32ohms through both coils in series measured at the climate control module connector. I even measured the same value when I went to the FC4 chassis harness connector on the side of the instrument panel by the drivers door ( left side.)

Originally Posted by Han-S

Being a complete numpty when it comes to electronics I can't help answering your question.

But are you considering adding a 1A fuse into this jumperline to protect the PCBA?
I have done this about a year ago because it has a burned track, still going strong.

Originally Posted by xalty

https://ibb.co/n0J0gp6

zero brain cells required to do it the right way.

this one took out the aux pump driver (v8 only) which is right behind pin 5. that one is a little trickier to do

Originally Posted by kr98664

Just thinking out loud. Before installing the Fling Dung brand DCCV, did you have the same exact symptoms? Full uncommanded heat after some time in use, and then working normal again for a little while after inactivity, right? That certainly sounds like your resettable fuses are opening and closing in response to exceeding their current rating. Just wondering if the symptoms changed at all with the replacement DCCV.

One gotcha with resistance readings. Most likely those were recorded at ambient temperature. Did you ever try measuring resistance when the system was misbehaving? The wires inside a coil typically have only a thin varnish insulation. With heat, that varnish can break down and create a short circuit. Once everything cools, current flow returns to normal. Or even if nothing is shorting out, some conductors behave differently at elevated temperatures (such as the filament in an incandescent bulb, for an extreme example). And while measuring resistance is fine and dandy, whenever possible I like to take an amperage reading. That's what really matters. I'd be curious if you can get the system to fail again, and then take either a resistance or amperage (preferred) value through the DCCV coils while still warm.

FWIW, on my '02, I measured just under 15 ohms and 0.85 amps for each coil at room temperature:

https://www.jaguarforums.com/forum/s...repair-251854/

Originally Posted by xalty

Chinese DCCV used in my last repair already failed. Gets hung up and needs to be slapped with prybar to work again.

My other chinese valve works good except at WOT when the ac is clutched off and the water pump flow forces the valves open. Your mileage may vary with those 30 buck specials