Discussion
When running the AC for long periods the ignition switch (and wires behind it) get blazing hot. (too hot to hold any length of time) I'm thinking this is what caused my switch failure a few months ago. Also the volts drop from 13.5 to anywhere from 12.5 to 10.8 depending on which speed the fan blower is running.
Everything works well though.
Does anyone else have this occurr?
thanks
jeff
Everything works well though.
Does anyone else have this occurr?
thanks
jeff
This sounds very familiar, in my GTR it is also dropping down to 11V when AC is on. Discussed that once ith the factory and they told me not to be concerned. Probably this really is no problem because the alternator is fully charging the battery and when I switch off the fans and AC, I read again about 13V. Just wonder what the voltmeter is actually measuring?
My mechanic recommended to replace all wires from the battery to the fuse box and from the alternator to the starter, because he thinks the diameter is too small. Should I do that?
My mechanic recommended to replace all wires from the battery to the fuse box and from the alternator to the starter, because he thinks the diameter is too small. Should I do that?
When I created my Ultima wiring schematic by taking the Ultima loom apart and recording every circuit, there were many areas where I noticed that the wiring seemed thin for the loads it would carry.
Jeff, since I don't have A/C, I've not experienced your problem, but if you check on your schematic, try and identify the wires that are getting hot and we can discuss the solution.
Jack
Jeff, since I don't have A/C, I've not experienced your problem, but if you check on your schematic, try and identify the wires that are getting hot and we can discuss the solution.
Jack
ultimacz said:
Just wonder what the voltmeter is actually measuring?
The switched ignition circuit under the dash. If there is a heavy current draw on this circuit, that should be through a relay, then you would note a localised voltage drop.
ultimacz said:
My mechanic recommended to replace all wires from the battery to the fuse box and from the alternator to the starter, because he thinks the diameter is too small. Should I do that?
I don't think that this is a problem area on the Ultima loom at all. The wiring from the battery tot he fuse box is OK for the standard equipment that is connected. If you have fitted a fancy Hi-Fi or other significant loads then you may need to do something different.
There is nothing wrong with the std alternator wiring at all. In fact it's actually quite cunning. The thick brown power out from the alt loops round the engine bay and up to the starter. The brown wire should be plenty thick enough for the current coming from the alt and it will then piggy back on the ultra-thick starter cable for most of the run back to the battery.
Like Jack I don't have A/C and haven't seen any issues with excessive current on the blower motor circuit (which looks the same for both A/C and plain heater). The wiring for the A/C fans, clutch, etc do look a little thin however and it maybe that they would benefit from being driven through a relay.
The currents involved in these components are not beyond what a even a cheap and cheerful domestic meter can handle. Can you take the earth off the blower cable and measure the current going through it on full? Also can you measure the current going to the condenser fan?
It sounds like it may not be a general problem so the excessive current could be down to another component that is misbehaving.
Not relevant to your problem but related. If anyone is going to fit an MSD Ignition box I can thoroughly recommend fitting a thick (same cross-section as the brown) wire from the battery to the engine bay before they close up the sidepods. Fitting it after is a pain! (as both myself and Stig seem to have found out independently
) You need to do this because the only +ve high current feeds to the engine bay are to the starter and alternator. These produce serious amounts of junk on the supply when operating and it will upset the electronics on the MSD box (or other EFI boxes) if not isolated properly.I had this problem, but in my case the ignition switch got very hot but the wires remained cold. Are you sure the wires are getting hot or is this just conducted heat from the switch? I changed the ignition switch and this cured the problem. (High resistance somewhere in the switch?)
The cables used in the Ultima loom must be of the high performance, thin walled variety. These have a larger number of thinner wires in the core and can carry more than twice the current of conventional cables of the same cross-sectional area, therefore they need to be only half the size (approx) of "normal" cables to have the same performance.
The cables used in the Ultima loom must be of the high performance, thin walled variety. These have a larger number of thinner wires in the core and can carry more than twice the current of conventional cables of the same cross-sectional area, therefore they need to be only half the size (approx) of "normal" cables to have the same performance.
Everything works OK. But the factory ignition switch failed stranding me in the middle of a 20 mile long bridge across a Gator infested Bayou in Louisiana.
Just wondering if this is normal since the new switch gets hot also, only when the AC is on.
Sounds like it's normal. So I'll drive it 'til it breaks
Jeff
Just wondering if this is normal since the new switch gets hot also, only when the AC is on.
Sounds like it's normal. So I'll drive it 'til it breaks
Jeff
Steve_D said:
Jeff
If your analysis of the problem points to it only happening when the A/C is on then it has to be worth the effort of climbing under the dash and fitting a relay to the A/C.
But I presume that will only work if the excess heat is from the wire supplying the blower unit under the dash. What if it's due to the supply to the condensor fan? Or is that already supplied via a relay?
Bob
Who's about to fit his cockpit and is thinking about fitting a relay ...
Steve_D said:
I did already suggest isolating both and checking the current drawn.
You did indeed Steve!
I connected my battery up yesterday while having the alarm fitted and am now able to check out some of the circuits. The blower fan draws 3.4, 4.5 and 5.6 amps at each of the 3 positions on the switch.
I couldn't get the A/C condenser fan to work, I presume it's because there's nothing connected to the pressure switch? I'm not sure how this all works, will simply shorting the pressure switch wires get the fan running?
Bob
Steve_D said:
If all you’re doing is checking current I would just unplug the fan and bring a temporary supply to it.
Good thinking - I was also keen to just check everything works before hiding it all under the dash! It also wouldn't tell me if there's a relay already in the circuit to the condenser fan.
Edited to add joined the A/C pressure switch wires together this afternoon and condenser fan worked fine and is supplied via relay.
Steve_D said:
The blower alone is more than I would want to take through the switch bearing in mind all the other Ign. Switched circuits it is taking.
OK - I don't know much about these things. So probably better to take a live feed from the fusebox to the blower via a relay.
Bob
>> Edited by BobM on Saturday 6th September 20:46
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