If you have not noticed or heard, I’ve opened the US Electricar.net store for USE owners so they can get repairs and parts to keep their vehicles running. There are links on this blog to take you there. Enjoy!

This morning I headed over to the hardware store to see if they had any 3/8″ fuel line to help adapt the 5/8″ heater hose to the 3/8″ barb. The fuel line was difficult to push onto the barb even with lubrication. In fact I had to use the coolant bottle from my spares that had the barb cut off. This allows the fuel line to barely fit over the barbless inlet. At least it worked. Then with some lube the 5/8″ heater hose fit snugly over the fuel line. A hose clamp made the whole thing water tight. This is what prevented the truck from being finished last night.

The heater element pulls about 8.5 amps at 321vdc. That’s over 2700 watts! The air sure gets warm quickly. On the drive to work I watched the thermometer that I stuck into the vent. It peaked at 130F or so, and then the over temp sensor would shut off the heating element. The temp at the vent would drop to about 105F, then the element would come back on. It was so nice to have a real heater for a change!!!! The bad news is that the heater uses 2.7kwh. So it’s a bit of a load for my small pack.

The original heater hoses were fairly brittle. When I clamped them with long nose vice grips they cracked and leaked. So the heater got all new hoses. I’m a little concerned about using 100% coolant and no water. I may siphon some coolant out and add water. Ethylene Glycol is not as efficient at 100% concentration. I used silica free coolant. A large syringe really helped when I had to prime the pump or remove coolant without any spilling. I used a Dremel tool and fiberglass cutoff wheel to shorten the inboard mounting tab on the Hotstart heater housing. It was a lot faster than using the mill because I didn’t have to figure out a jig. Cut off enough of the tab to just remove the 2 inboard mounting holes and no more. Otherwise there won’t be enough material to keep the seal in compression.

BTW, the heater core tubes coming through the firewall were aluminum. Be careful when adding or removing hoses!

This heater upgrade could really be polished off with a variable temperature control. I thought about it today. The control circuit could be placed with the heater relay in the battery box, or if it fit, into the heater box. The heater box is a bit cramped. I suspect the circuit will need a source of metal around to thermally sink the fets to. The heater box might be too warm, but it would be the most convenient. Maybe the engine compartment is a decent mounting place for at least initial testing. This circuit would also lighten the load on the battery pack by allowing the heater to run at settings less than full current.

The temperature control knob would mount next to the heater button the dash. I think it will fit onto that small cover. An LED would be good to indicate if temperature control is on or not, and at what rate it’s pulsing. Maybe zero to 100hz would do it. The schematic is in pieces but has enough info that I could start on circuit testing in the future.

A lesson learned from an ACP failure that I witnessed, will give the circuit an indicator signal that is actually enabled when there is high voltage present at the output of the fets. This makes sure that if there is a fet failure, that there will be an indicator to tell me that.

I used a Dremel tool and fiberglass cutoff wheel to shorten the inboard mounting tab of the Kim Hotstart heater housing. It was much faster than using the mill because I didn’t have to jig up the heater to machine it.

Don’t forget to prime the pump!! It’s a pain in the butt!! You will smoke your heater if you don’t!!! You can shine a flashlight behind the coolant bottle to make the coolant glow. When you look inside the bottle or through the wall of the inlet, you can see both huge bubbles or microscopic bubbles. Both of them should be moving to show that the coolant is flowing. I used my aux battery to spin the pump without running the heater. A 50/50 mix of coolant and water will help with the priming as coolant is way too thick.

I worked all afternoon and evening putting in a Kim Hotstart heater in the #1 truck. It’s going to be a cold week. I need a better heater. I was nearly done tonight with the swap and found that there is a 5/8″ heater hose that has to fit on a 3/8″ barb. There was a smaller piece of hose adapting the two together, but I nicked it with the knife as I was removing it. The stores were closed by the time I figured this out. So the truck is not going to drive me to work in the morning.

The coolant bottle also had to be rotated 180 degrees because it would be in the way of the air conditioning hose that goes around the firewall, when I add the AC that is. So a couple more holes had to be drilled.

Hopefully the Kim Hotstart heater will have decent longevity. It’s a 240vac 1500w heater running at 300-400vdc. That’s about 2700w. At least the plastic body helps get rid of ground fault potential.

Here is the Hotstart heater before it has one of the mounting tabs shortened. Next to it is the wiring that I add to make it easy to test and remove if needed. The small connectors at the end of each of the wires are from the Hotstart. The high voltage connector with the green and blue 10ga wires, has 4 positions with two of them empty between the pins to help prevent arc-over. The 3 position connector with the 2 yellow wires is for the temperature sensor. The pump motor shown in other images, has a 2 pin connector. This keeps connectors from being confused during reassembly.Hotstart Heater.

This #1 truck was built very late in the program. 1996. So it has some improvements. Tonight I found that the hoses attached to the pump and the heater had a large diameter stainless spring inside to keep the hoses from collapsing. This could be helpful.[/caption]

The Z shaped hose that connects the pump to the heater, tends to kink at both ends. These stainless springs took care of that. I should retrofit the #2 truck with the same hose springs.

As soon as I can adapt the 5/8″ hose to the 3/8″ barb, the truck will be ready. I also pre-primed the pump by adding coolant to the heater and the pump with a syringe, then spinning the pump before it will be put back into the truck.

I was not able to test the original heater output before the swap, to generate a temperature versus time plot.


Last night I finally got the blower to stop running when the selector switch was in the off position. It turns out that USE wired it in such a way that it grabbed power from an always on source. Although it appeared that I also added to the issue. The blower was tied to a 3 amp circuit for power. So when I turned the blower up to high, it popped the 3 amp fuse. Now it’s rewired straight to the heater/ac fuse and gets all the juice it needs. The 3 amp circuit is now independent and works fine. All of this also made me update my heater/ac schematic yet again. I have not looked at an air conditioned truck before so I am not sure if my wiring will match. I made this system work the way that is the most useful and makes the most sense. This truck was an early version and their ac wiring was not tested enough to find any bugs. The big thing is that the heater and ac never worked from day one according to the original owner. So I think now the system is wired correctly. Buying the factory S10 manuals used from Ebay made a huge difference in diagnosing the electrical and vacuum issues with the #2 truck!

I also bumped the regen in first gear to the maximum. The first time I tried it the truck shuddered like mad, but without faulting. The pack voltage jumped from about 330v to 380v. There is a limit to the voltage and I exceeded it. This really points out how high the pack impedance really is. This pack is shot.

When the dash gets taken apart the orange heater switch has to get pulled out. So the small panel that it is mounted to clips into the dash bezel. One of the molded in tabs snapped off. I used my standard repair of CA (CyanoAcrylate) and Kelvar strands to fix it. It may make the tabs too stiff which would require them to be shaved down a bit so they can be installed/removed easily.

I also added 2 12v batteries to the #2 truck’s pack. The pack is showing such low voltage output as the seasonal temperatures get down into the 30’s. Then the charge curve had to be increase up to 400v since there are now 27 batteries in the pack. That should get the truck around the block over the next few months. I did notice that the 592AE processor would not accept a full download of the .set file. I think it might be because the file was for a 5B5AA processor. The only real difference is in the checksums being different. So I went through manually and changed the several settings to match the nicad settings so the truck will charge higher and run on a lower pack voltage if needed.

I have this other circuit design that looks like it could be modified
and adapted to actually giving real temperature control to the USE heaters.
Since the heater element runs on pack voltage this would be a high voltage
control with a pot on the dash that changes the temperature. The pot
would be opto isolated for safety. It would be just a single board
that connects after the heater relay to pack voltage, and uses high
voltage fets for controlling the power to the heater element.
Depending on the space available, it could mount in the heater box

Yes!!!!! The air conditioning is fixed!!! What a bunch of work that was!! The story goes like this. The factory had a learning curve as they built their first few vehicles. The #2 truck was an early version. So the wiring for the AC and heater had been set up in a way that was very untested. Instead of a switch to turn on two relays, they used one of the pots that is part of the temperature control on the dash. As the pot is rotated, it slowly brings the voltage up to the coils of the two relays. The problem is that the relays don’t come on at the same time!! So the heating element would turn on long before the water pump would and smoke the heating element. That’s why this truck never had a functional heater. The air conditioning had a bad crimp at the AC controller plus the ground for the AC controller was corroded badly. I had to clean the pins and sockets up for each of the 12 connections. That’s all it took!

I also added the lighted dash switch that most trucks have to turn on the heater. Now the AC and the heater can be run completely independent of each other, or at the same time. Nice!!

The wiring to the AC compressor and controller can reach the top of the Dolphin. This will allow me to test my spare AC parts.

What really made this debug work well, was spending a week making a schematic from crummy notes that had been faxed from the factory 12 years ago. It was a lot of work. But it made the debug of the AC system far better. Now I have a massive 18″ x 24″ drawing of the entire AC and heating system. This never existed before! I’d like to add AC to the #1 truck now that I have a schematic, parts, and wiring.

The only odd item left to repair is the heater/AC blower. It’s always on. Even when the selector knob is off, the blower runs. It’s speed can even be adjusted from the fan switch. I didn’t see any rigged wiring. But I suspect the wiring was modified somewhere and it needs to get fixed.

A rough schematic for the precharge board is done. Data sheets for many of the components have been found. So finding substitutes for these obsolete parts will be easier now.

This whole precharge project could be adapted to giving the heater element a variable temperature control instead of being just on or off.

A couple of mornings ago, it was 50F outside. The #2 truck has been
outside all night and everything about it was cold soaked. So I fired
up the Hotstart heater. The air temp through the vents or the
defroster went from 50F to 100F in about 2 minutes. I only had the
radio clock to judge by. From 100F and higher it warmed up more
slowly. I’ll use a timer and wait for colder weather for another test.
This time the Hotstart did not open the circuit due to hitting the
over temp threshold.

A 50 degree delta in 2 minutes is a great improvement in heater
performance versus stock. At least it feels that way. I will also get
the data from the #1 truck’s heater so they can be compared side by side.

It’s also important that the brown lead coming directly off of the
heater pump motor be the one that is grounded. This pump won’t work spinning
backwards. The wiring that goes to the pump are different colors.

Here are 3 full res pics of the converted heater box using the Kim
Hotstart heater. I’ve added Molex connectors to each item in the box
as it makes checking them vastly easier. The first pic is a bit
deceiving as the original red Rusco heater is quite a bit smaller in

Don’t ever forget to verify that the pump is primed and actually
moving water!!!!

Red can is the original style Rusco heater.

Red can is the original style Rusco heater.

Pump and Hostart closeup. Note simple bracket to hold Hotstart in place.

Pump and Hostart closeup. Note simple bracket to hold Hotstart in place.

Complete view of heater box with Hotstart heater and pump.

Complete view of heater box with Hotstart heater and pump.

Hotstart label.

Hotstart label.

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